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  • National-scale assessment of pan evaporation models across different climatic zones of China
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-10
    Yu Feng, Yue Jia, Qingwen Zhang, Daozhi Gong, Ningbo Cui

    Evaporation is an essential component in hydrological processes, and accurate estimation of evaporation is of importance for sustainable management of water resources. This study conducted a national-scale assessment of different models for pan evaporation (Epan) estimation at 178 meteorological stations across different climatic zones of China, including the temperate continental zone (TCZ), temperate monsoon zone (TMZ), mountain plateau zone (MPZ) and subtropical monsoon zone (SMZ). Firstly, three data-driven models, including extreme learning machine (ELM), artificial neural networks optimized by particle swarm optimization (PSO-ANN) and genetic algorithm (GA-ANN), were trained with nine input combinations of climatic variables. The performance of the 27 proposed models along with the empirical Stephens and Stewart (SS) and physically-based PenPan models were investigated and compared using relative root mean square error (RRMSE), Nash-Sutcliffe coefficient (NS) and mean absolute error (MAE). The three statistical indicators were further normalized to global performance indicator (GPI), by which all the evaluated models can be easily ranked. The results showed that the data-driven models with complete inputs generally obtained more accurate Epan estimation, where the ELM model with full input data provided the best accuracy at 69.6% stations, with average RRMSE of 12.5%∼15.2%, NS of 0.909∼0.936 and MAE of 11.7∼19.9 mm/m. Air temperature was found to be the most influential parameter to data-driven models, followed by sunshine duration, wind speed and relative humidity. The SS model provided slightly better results in MPZ and TCZ, and slightly less accurate results in SMZ and TMZ, compared with the data-driven models under the same input conditions. Overall, ELM was recommended as the best model for Epan estimation when all the selected climatic data are available, while temperature-based PSO-ANN is recommended in MPZ and SMZ and temperature-based GA-ANN is recommended in TCZ and TMZ when the other climatic data are missing.

    更新日期:2018-07-12
  • An experimental detrending approach to attributing change of pan evaporation in comparison with the traditional partial differential method
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-11
    Tingting Wang, Fubao Sun, Jun Xia, Wenbin Liu, Yanfang Sang, Hong Wang

    In predicting how droughts and hydrological cycles might change in a changing climate, change of pan evaporation (Epan) is one crucial element to be understood. The derived partial differential (PD) form of the PenPan equation is a prevailing attribution approach worldwide. However, small bias exists and the application of PD method is limited within the derivation of partial differential form of the equation, which impede the attribution analysis in hydrology. Here we designed a series of numerical experiments by detrending each climatic variable, i.e., an experimental detrending (ED) approach, to attribute changes of Epan over China. We compared the attribution results using these two methods and further analyzed the plausible advantages of ED approach. The comparison shows that both the ED approach and PD method perform well in attributing changes of Epan and to the input variables in China over 1960-2017. The first advantage of ED approach is that it can help make robust adjustment for the PD method in attribution analysis. Another advantage lies in its ability to attribute to the observed meteorological variables in China when the PD method fails to quantify the contribution of relative humidity and air temperature in net radiation. We highlight that the ED approach is recommended in attribution analysis for hydrologic research. Together with the adjusted PD method, both methods can assist a better understanding and prediction of water-energy cycles change in a changing climate.

    更新日期:2018-07-12
  • Effects of irrigation-induced water table fluctuation on arsenic mobilization in the unsaturated zone of the Datong Basin, northern China
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-11
    Ziyi Xiao, Xianjun Xie, Kunfu Pi, Yijun Yan, Junxia Li, Zeyong Chi, Kun Qian, Yanxin Wang

    High level of arsenic-containing groundwater has been used for irrigation purposes for several decades in Asia, leading to fluctuating water table and redox conditions in the unsaturated zone, thereby potentially affecting the mobilization of arsenic in the unsaturated and saturated zones. A field plot experiment was conducted in the arsenic - affected area of the Datong Basin, China to determine the effects of irrigation return flow on the hydrogeochemical behavior of arsenic and iron in the unsaturated zone. High-arsenic groundwater was extracted from a shallow aquifer far from the irrigation site and used as irrigation water. Soil water/shallow groundwater and soil/sediment samples were collected at different depths from the field site during the experiment. Water samples were analyzed to determine hydrochemical properties and arsenic concentrations, and soil/sediment samples were analyzed to determine total iron and arsenic. Infiltration of irrigation water into the unsaturated zone led to fluctuations in the water table, varying redox conditions, and the redistribution of arsenic and iron in the near-surface soil/sediment. Soil/sediment bulk geochemical analysis results indicate obvious increases of arsenic and iron in topsoil after irrigation. Infiltration of irrigation water carrying organic matter, sulfate, and nitrate into the subsurface affects the (bio)geochemistry of the unsaturated and saturated zones, and ultimately the behavior of arsenic and iron. Geochemical modeling results suggest desorption and leaching processes are responsible for the temporal changes of arsenic concentrations in both pore water, groundwater and sediment during irrigation. The results of this study indicate that flood irrigation using arsenic-contaminated groundwater should be controlled and gradually replaced by drip irrigation, sprinkler irrigation or irrigation using non-contaminated water resources to mitigate arsenic accumulation in the unsaturated zone and shallow groundwater.

    更新日期:2018-07-12
  • Effect of Eucalyptus plantations, geology, and precipitation variability on water resources in upland intermittent catchments
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-11
    P. Evan Dresel, Joshua F. Dean, Fahmida Perveen, John A. Webb, Peter Hekmeijer, S. Michael Adelana, Edoardo Daly

    Land-use change and climate variability have the potential to alter river flow and groundwater resources dramatically, especially by modifying actual evapotranspiration. Seven catchments with intermittent flow dominated by either winter-active perennial pastures (4 catchments) or Eucalyptus globulus plantations (3 catchments), located in 3 geologic settings of southeastern Australia, were studied for over 6 years to determine the primary controls on water resources. Groundwater levels in the pasture sites were stable through the 2011-2016 study period, while levels in the plantations declined in the same period. Streamflow occurred mainly during winter. Annual streamflow showed no difference clearly attributable to pasture versus plantation land use. The presence of grass buffers along streams enhances groundwater recharge and saturation-dependent overland flow, reducing the impacts of the plantations on streamflow. Site water balances indicated that the average annual actual evapotranspiration was 87-93% of precipitation for pasture catchments and 102-108% of precipitation for plantation catchments. Actual evapotranspiration greater than precipitation at the plantations was attributed to uptake of groundwater by the root system in parts of the catchments. Thus, change to groundwater storage is a critical component in the water balance. Actual evapotranspiration from pasture catchments was higher than previously estimated from global pasture and cropping data, instead matching global precipitation versus actual evapotranspiration curves for treed catchments.

    更新日期:2018-07-12
  • Double-sided stochastic chance-constrained linear fractional programming model for managing irrigation water under uncertainty
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-11
    Chenglong Zhang, Bernard A. Engel, Ping Guo, Xiao Liu, Shanshan Guo, Fan Zhang, Youzhi Wang

    A double-sided stochastic chance-constrained linear fractional programming (DSCLFP) model is developed for managing irrigation water under uncertainty. The model is developed by incorporating double-sided stochastic chance-constrained programming (DSCCP) into a linear fractional programming (LFP) optimization framework. It can address ratio optimization problems with double-sided randomness (i.e. both left-hand and right-hand sides). More importantly, it also improves upon the existing stochastic chance-constrained programming for handing random uncertainties in the left-hand and right-hand sides of constraints simultaneously. A non-equivalent but sufficient linearization form of the DSCLFP is provided and proved, which will greatly reduce the computational burden. Then, the model is applied to a case study in Yingke Irrigation District (YID) in the middle reaches of the Heihe River Basin, northwest China. Four confidence levels (e.g. α i = 0.85, 0.90, 0.95 and 0.99) are provided to examine and compare the results. The objective function values are slightly decreased from 5.284 Yuan/m3 to 5.276 Yuan/m3 when α i level is raised from 0.85 to 0.99. The results from the DSCLFP can identify desired irrigation water allocation plans under the objective function of maximizing water productivity under different confidence levels. Therefore, the results can provide tradeoffs among water productivity, confidence level and constraint-violation risk level. Moreover, comparisons with double-sided stochastic chance-constrained linear programming (DSCLP) model and deterministic model are introduced to highlight advantages and feasibility of the developed model. Therefore, these results can provide decision-support for managers in arid areas.

    更新日期:2018-07-12
  • Spatial Modelling of the Regulating Function of the Huangqihai Lake Wetland Ecosystem
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-11
    YiCheng Fu, Jinyong Zhao, Wenqi Peng, Guoping Zhu, Zhanjun Quan, Chunhui Li

    The regulating function is the least understood but probably most valuable service provided by an ecosystem. To estimate the impact of externalities on the regulating function of a wetland, we modelled the interdependence between activities that affect wetland characteristics and land utilization patterns. Nature-based solutions (NBS) can provide benefits for society, the economy and nature. The NBS solution for wetland bioremediation is proposed through a combination of ecosystem value provided by nature-based or artificial arable land. We constructed a model to simulate the dynamic spatial and temporal changes in the regulating function of a wetland to study the impact of agricultural and fishing activities on the functions and services of a wetland ecosystem. The model was used to determine the relationship between land use change, wetland range, water quality, and fish stocks. Huangqihai Lake (HQHL) is a relatively isolated lake in an area interlaced with agriculture and pasture zones. From 1973-2014, the “shrinkage” of the water area of HQHL approached 60%. Under the influence of humans and natural disturbances, the HQHL wetland faced enormous ecological risks, water pollution, area reduction, sharp biodiversity reduction, and fish extinction. The phosphorus (P) concentration seems to be a key factor affecting both the reed growth in the nearshore areas of the Huangqihai Lake wetland and the breeding of phytoplankton in the core lake water area. Dividing this value by the 25,821 hectares of the core wetland area affected by the reclamation, the cost per unit of lost fish production is USD$166/ha/yr. After deducting the externalities of the fishery, the net sustainable income from the conversion is USD$1717/ha. The spatial distribution of nutrient load externalities varies with the use of wetlands. In terms of fishery value, the additional nutrient load associated with the conversion of wetland uses would result in a reduction of at least 8% of the maximum sustainable yield. The conversion of wetland uses resulted in the loss of nutrient buffering functions. To compensate for the farmland's nutrient load buffer service, the government should provide arable land farmers USD$8.1M/yr. It is theoretically feasible to implement an ecosystem service payment system that can effectively compensate for the loss of nutrient buffer function caused by the conversion of wetlands. The approach based on BNS we described may also have value in other ecosystems where regulatory functions include similar mechanisms.

    更新日期:2018-07-12
  • The fate of urban springs: pumping-induced seawater intrusion in a phreatic cave
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-09
    Robert J. Scharping, K. Michael Garman, Ryan P. Henry, Prahathees J. Eswara, James R. Garey

    Sulphur Springs Cave is an extensive phreatic cavity that produces a large, historic spring in the middle of metropolitan Tampa, Florida, USA. The city of Tampa extracts groundwater from the spring to supplement municipal water supply and to support low-salinity habitat in the estuarine Hillsborough River. Extraction at this site has occurred for many decades, but has intensified since the early 2000s, rapidly increasing the salinity of the spring and cave water. The purpose of this study was to address the potential sources and mechanisms of saltwater intrusion at this site using historical and current hydrochemical data published in the literature and online by government agencies. We also explored the cave to identify point-sources of intrusion, and collected water and biological samples from inside the cave to identify potential ecosystem impacts of increasing cave salinity. From 1946 to present, Sulphur Springs water shifted from being fresh (specific conductance <500 µS cm-1) and of calcium-sulfate type to being brackish (specific conductance ∼5,000 µS cm-1 and higher) and of sodium-chloride type. We found numerous vents in the cave that issue saline, thermal, sulfidic water and host distinct microbial mat communities. These vents are likely connected to bedrock fractures that provide preferential flow-paths along which confined, deep-sourced saline water enters the freshwater portion of the aquifer, probably originating from the coastal mixing zone. Salinity increased at the spring during dry-season pumping activity and after wet-season recharge events, which likely increased artesian pressure in confined saline aquifer units. Salinization of Sulphur Springs may disrupt the cave microbe and stygobite communities and eventually make the spring unsuitable to maintain low-salinity habitat in the Hillsborough River.

    更新日期:2018-07-09
  • Morphological variability of the active Yellow River mouth under the new regime of riverine delivery
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-09
    Hongyu Ji, Shenliang Chen, Shunqi Pan, Congliang Xu, Chao Jiang, Yaoshen Fan

    The Yellow River subaqueous delta (YRSD), once the most rapid depo-center among river deltas worldwide, has been under the risks of subsidence and degradation due to the new regime of riverine delivery affected by human interventions. Utilizing hydrologic and bathymetric surveying datasets, we examined the latest regime of river input from the perspective of water-sediment relationship, and the responding morphological evolutionary processes of active YRSD over a period of 20 years between 1996 and 2016. Results show that new discharge regime is strongly interfered by the Water-Sediment Regulation Scheme (WSRS), characterized by a more drastic decline of sediment load than that of water discharge; more harmonious relationship between water and sediment discharges in the lower reach of the river to the sea; coarser sediment delivery and low suspended sediment concentration (SSC). We identified inverse erosion-accretion trends in the subaqueous region: net accretion of 0.15 m/yr in the active Yellow River mouth (AYRM) and severe erosion of -0.1 m/yr in the Gudong littoral zone (GDLZ). As the primary sink for sediment delivery, AYRM received approximately 68% of sediment delivery during the study period and sedimentation was mainly occurred in the shallower area where water depth was less than 10 m. In addition, recent morphological evolution of AYRM is found to have undergone through four stages, namely: moderate accretion (1996-2002), rapid accretion (2002-2007), reduced accretion (2007-2015) and rapid erosion (2015-2016). The new regime of riverine delivery presents multiple spatiotemporal scales in shaping deltaic morphology. Compared with the previous research, we present the morphological evolution of deltaic system over decadal timescale is strongly influenced by reduction of sediment supply derived from basin-scale human impacts, and the variability of subaqueous portion during the study period is closely related to inter-annual variability of river input. Besides, the building of AYRM is shaped by event-scale WSRS induced-floodwater, and decade-scale change of sediment pathway governed by frequent mouth channel migration. The results show, for the first time, that AYRM has experienced a significant erosion since the implementation of WSRS, with a decline of 99% sediment delivery in 2016 compared to the natural mode during 1950s. The results also indicate that to maintain the erosion-accretion balance of AYRM, an estimation of 41.4-62.3 Mt/yr sediment delivery should be kept. Due to the fluvial regime change from the natural to the highly human-regulated modes, the AYRM, as well as the whole YRSD, is expected to be transforming from the accretion to erosion states.

    更新日期:2018-07-09
  • Sensitivity of Drought Resilience-Vulnerability- Exposure to Hydrologic Ratios in Contiguous United States
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-09
    Anoop Valiya Veettil, Goutam Konapala, Ashok K. Mishra, Hong-Yi Li

    The atmospheric water supply and demand dynamics determine a region’s potential water resources. The hydrologic ratios, such as, aridity index, evaporation ratio and runoff coefficients are useful indicators to quantify the atmospheric water dynamics at watershed to regional scales. In this study, we developed a modeling framework using a machine learning approach to predict hydrologic ratios for watersheds located in contiguous United States (CONUS) by utilizing a set of climate, soil, vegetation, and topographic variables. Overall, the proposed modeling framework is able to simulate the hydrologic ratios at watershed scale with a considerable accuracy. The concept of non-parametric elasticity was applied to study the potential influence of the estimated hydrologic ratios on various drought characteristics (resilience, vulnerability, and exposure) for river basins located in CONUS. Spatial sensitivity of drought indicators to hydrologic ratios suggests that an increase in hydrologic ratios may result in augmentation of magnitude of drought indicators in majority of the river basins. Aridity index seems to have higher influence on drought characteristics in comparison to other hydrologic ratios. It was observed that the machine learning approach based on random forests algorithm can efficiently estimate the spatial distribution of hydrologic ratios provided sufficient data is available. In addition to that, the non-parametric based elasticity approach can identify the potential influence of hydrologic ratios on spatial drought characteristics.

    更新日期:2018-07-09
  • Simulation and forecasting of streamflows using machine learning models coupled with base flow separation
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-05
    Hakan Tongal, Martijn J. Booij

    Efficient simulation of rainfall–runoff relationships is one of the most complex problems owing to the high number of interrelated hydrological processes. It is well-known that machine learning models could fail in simulating streamflows from only meteorological variables in the absence of antecedent streamflow values. The main reason for this could be low and lagged relationships between streamflow and meteorological variables. To overcome this inefficiency, for the first time, we developed a simulation framework by coupling a base flow separation method to three machine learning methods. It was demonstrated that separating streamflow into different components such as base flow and surface flow can be useful for improving simulation and forecasting capabilities of machine learning models. We simulated streamflow in four rivers in the United States with Support Vector Regression (SVR), Artificial Neural Networks (ANNs) and Random Forest (RF) as a function of precipitation (P), temperature (T) and potential evapotranspiration (PET). We concluded that the base flow separation method improved the simulation performances of the machine learning models to a certain degree. Apart from the simulation scheme, we also employed a forecasting scheme by using the antecedent observed discharge values in addition to P, T, and PET. We discussed performances of models in simulation and forecasting of streamflow regarding model types, input structures and catchment dynamics in detail.

    更新日期:2018-07-08
  • Unsupervised Ensemble Kalman Filtering with an Uncertain Constraint for Land Hydrological Data Assimilation
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-05
    M. Khaki, B. Ait-El-Fquih, I. Hoteit, E. Forootan, J. Awange, M. Kuhn

    The standard ensemble data assimilation schemes often violate the dynamical balances of hydrological models, in particular, the fundamental water balance equation, which relates water storage and water flux changes. The present study aims at extending the recently introduced Weak Constrained Ensemble Kalman Filter (WCEnKF) to a more general framework, namely unsupervised WCEnKF (UWCEnKF), in which the covariance of the water balance model is no longer known, thus requiring its estimation along with the model state variables. This extension is introduced because WCEnKF was found to be strongly sensitive to the (manual) choice of this covariance. The proposed UWCEnKF, on the other hand, provides a more general unsupervised framework that does not impose any (manual, thus heuristic) value of this covariance, but suggests an estimation of it, from the observations, along with the state. The new approach is tested based on numerical experiments of assimilating Terrestrial Water Storage (TWS) from Gravity Recovery and Climate Experiment (GRACE) and remotely sensed soil moisture data into a hydrological model. The experiments are conducted over different river basins, comparing WCEnKF, UWCEnKF, and the standard EnKF. In this setup, the UWCEnKF constrains the system state variables with TWS changes, precipitation, evaporation, and discharge data to balance the summation of water storage simulations. In-situ groundwater and soil moisture measurements are used to validate the results of the UWCEnKF and to evaluate its performances against the EnKF. Our numerical results clearly suggest that the proposed framework provides more accurate estimates of groundwater storage changes and soil moisture than WCEnKF and EnKF over the different studied basins.

    更新日期:2018-07-08
  • Emulator-enabled approximate Bayesian computation (ABC) and uncertainty analysis for computationally expensive groundwater models
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-05
    Tao Cui, Luk Peeters, Dan Pagendam, Trevor Pickett, Huidong Jin, Russell S. Crosbie, Matthias Raiber, David W. Rassam, Mat Gilfedder

    Bayesian inference provides a mathematically elegant and robust approach to constrain numerical model predictions with system knowledge and observations. Technical challenges, such as evaluating a large number of models with long runtimes, have restricted the application of Bayesian inference to groundwater modeling. To overcome such technical challenges, we use Gaussian process emulators to replace a transient regional groundwater MODFLOW model for computing objective functions during model constraining. The regional model is designed to assess the potential impact of a proposed coal seam gas (CSG) development on groundwater levels in the Richmond River catchment, Clarence-Moreton Basin, Australia. The emulators were trained using 4000 snapshots derived from the MODFLOW model and subsequently used to replace the MODFLOW model in an Approximate Bayesian Computation (ABC) scheme. ABC was deemed the more appropriate choice as it relaxes the need to derive an explicit likelihood function that the formal Bayesian analysis requires. The study demonstrated the flexibility of the Gaussian process emulators, which can accurately reproduce the original model behavior at a fraction of the computational cost (from hours to seconds). The gain in computational efficiency using the proposed approach allows the global calibration and uncertainty algorithms to become more feasible for computationally demanding groundwater models. Based on the ABC analysis, the probability for the simulated CSG development causing a water table change of more than 0.2 m was less than 5%. In addition to a probabilistic estimate of the prediction, an added value of emulator-assisted ABC inference is providing information on the extent to which observations can constrain parameters and predictions, as well as the flexibility to include various quantitative and qualitative parameter constraining information.

    更新日期:2018-07-08
  • Influence of the β parameter of the Haverkamp model on the transient soil water infiltration curve
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-05
    B. Latorre, D. Moret-Fernández, L. Lassabatere, M. Rahmati, M.V. López, R. Angulo-Jaramillo, R. Sorando, F. Comín, J.J. Jiménez

    Soil water infiltration can be described with the quasi-analytical Haverkamp et al. (1994) equation, defined by the hydraulic conductivity (Ks), sorptivity (S) and the β parameter. Ks and S are commonly estimated from the transient cumulative infiltration curve, using a constant β value. The objective of this work was to study the influence of β on the estimation of Ks and S. The study was first performed on synthetic 1-D infiltration curves generated at different infiltration times for loam sandy, loamy and silty soils, and next extrapolated to a 3-D loam synthetic soil and on 10 infiltrations curves measured on the field with a disc infiltrometer on different types of soils. The infiltration measurements lasted between 600 and 900 s. The results showed that, while early infiltration times (i.e. 100 s) promoted good estimations for S, longer infiltrations (i.e. 1.000s) were required to estimate accurately Ks. Only very long infiltration (i.e. 10.000 s) allowed defining the actual β value. A similar behaviour was observed for the 3-D infiltration measurements. Except for β, significant relationships (R2 = 0.99) were obtained between the Ks and S of the three theoretical soils and the corresponding values calculated by optimizing the three hydraulic parameters on 2.000 s 1-D infiltration curves. The large confidence interval observed in β (between 0.3 and 2.0) resulted from the fact that β had a small effect on the infiltration curve. A significant relationship (R2 = 0.99) was also obtained between the Ks and S optimized from the exprimental curves using a β = 1.1 and the corresponding values obtained by simultaneous optimization of the three hydraulic parameters. These results demonstrated that S and Ks can be accurately estimated using a constant β and that downward infiltration is not an appropriate procedure to estimate β.

    更新日期:2018-07-08
  • A Lattice Boltzmann model for 2D fractional advection-dispersion equation: Theory and application
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-05
    Feng Wang, Xiaoxian Zhang, Xiaojun Shen, Jingsheng Sun

    Natural soils and aquifers are inherently heterogenous and chemical transport through them is anomalous characterized by an early arrival followed by a persistent tail. How to describe such anomalous phenomena has been an interest and, as a result, a number of approaches have been proposed over the past few decades. Among others, the fractional advection-dispersion equation (FADE) is a model able to describe anomalous transport when the dispersion is regional rather than local as presumed in the classical advection-dispersion equation. Practical application of FADE needs numerical solutions, which is challenging because its spatial discretization gives rise to a full coefficient matrix. In this paper, we propose a Lattice Boltzmann model to solve the two-dimensional FADE. Given that the anomalous dispersion in soils and aquifers is hydrodynamic and caused by spatial variation in water velocity across the pore space and that the chemical plume spreads preferentially along the mean water-flow direction, the dispersion coefficient and the order of the fractional derivative should be both anisotropic. The anisotropies are solved by the two-relaxation time Lattice Boltzmann model using different relaxation parameters in different directions. Compared with existing numerical methods for the FADE, the proposed model has advantages that it is explicit, second-order accurate in both time and space, mass-conservative, and free of numerical dispersion; its stability is independent of dispersion coefficient. We verify the model against the analytical solution of a benchmark problem and then apply it to simulate Cl- movement in a tracer experiment conducted on an up-catchment hillslope. The results show that the FADE with backward skewness can reproduce the breakthrough curves measured from the experiment.

    更新日期:2018-07-08
  • Regionalization study of maximum daily temperature based on grid data by an objective hybrid clustering approach
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-06
    Yue Yu, Quanxi Shao, Zhaohui Lin

    Regionalization plays an important role in climatology and hydrology research, as it can be used to understand the changing pattern of a hydroclimate variable better and explore its underlying drivers effectively by identifying homogeneous regions which are determined by topography and climatic conditions. However, as climatic drivers change over time, homogeneous regions should vary when the intra-annual patterns are of interest. In this paper we investigate the regionalization and changing patterns of maximum daily temperature in China based on the maximum air temperature (Tmax) derived from the CN05.1 daily surface air temperature gridded data from 1981 to 2010. We also propose an objective variable-based regionalization approach by combining the rotated empirical orthogonal function (REOF) method and K-means clustering analysis, to determine homogeneous regions effectively for such a large volume of daily grid data. The REOF approach is not able to identify discrete regional boundaries easily, but it is efficient at determining the number of regions and their rough spatial location. Furthermore, while clustering analysis suffers from convergence when the number of observations is large, it is able to provide clean boundaries between regions. The hybrid method tends to overcome their individual disadvantages while maintaining their individual advantages. The results show that the patterns of homogeneous regions have distinct features in both summer and winter seasons. The reasonableness of regionalization is then examined by the first principal component within regions, which shows the homogeneity within regions, and the scatterplots of Tmax time series between regions, which show the heterogeneity between regions. Furthermore, the boxplots of normalized Tmax within regions for both summer and winter seasons also clearly show the different characteristics of inter-annual variability in each region. In order to reveal detailed process of the change in the number and pattern of regions, we further conducted the regionalization for individual months and explored the potential linkages between regionalization and climatic conditions over time. This research is noteworthy in promoting research on regionalization with consideration of seasonal and intra-annual variation as well as extreme temperature events. The proposed hybrid regionalization method is broadly applicable to other regionalization studies.

    更新日期:2018-07-08
  • Evaporation from bare soil: Lysimeter experiments in sand dams interpreted using conceptual and numerical models
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-06
    Ruth Quinn, Alison Parker, Ken Rushton

    Unlike evaporation from open water, the magnitude of evaporation from bare soil decreases as the water table falls. Bare soil evaporation studies have included field and laboratory experiments, mathematical formulations and semi-empirical models. However, there is only limited field information, especially concerning evaporation from bare sand. The semi-empirical approach of the FAO1 Irrigation and Drainage Paper 56, which contains guidelines for computing crop water requirements, can be adapted for bare soil evaporation with a three stage process. The suitability of the FAO 56 approach for bare sand evaporation is investigated by installing lysimeters in sand dams. Sand dams are shallow groundwater storage systems, which are designed on the assumption of reduced evaporation as the water table falls. The field results from the lysimeters are simulated adequately by a water balance model based on FAO 56 with an additional component to represent both the difference between the variable saturation with depth, which occurs in practice, and the assumption in standard water balance models of a sudden change from dry to fully-saturated conditions at the water table. This study demonstrates and quantifies the reduction in bare soil evaporation compared to open water or cropped areas and confirms the validity of the three stage FAO semi-empirical approach.

    更新日期:2018-07-08
  • Spatio-temporal modelling of the status of groundwater droughts
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-06
    B.P. Marchant, J.P. Bloomfield

    An empirical (geo)statistical modelling scheme is developed to address the challenges of modelling the severity and distribution of groundwater droughts given their spatially and temporally heterogeneous nature and given typically highly irregular groundwater level observations in space and time. The scheme is tested using GWL measurements from 948 observation boreholes across the Chalk aquifer (UK) to estimate monthly groundwater drought status from 1960 to 2013. For each borehole, monthly GWLs are simulated using empirical mixed models where the fixed effects are based on applying an impulse response function to the local monthly precipitation. Modelled GWLs are standardised using the Standardised Groundwater Index (SGI) and the monthly SGI values interpolated across the aquifer to produce spatially distributed monthly maps of SGI drought status for 54 years for the Chalk. The mixed models include fewer parameters than comparable lumped parameter groundwater models while explaining a similar proportion (more than 65%) of GWL variation. In addition, the empirical modelling approach enables confidence bounds on the predicted GWLs and SGI values to be estimated without the need for prior information about catchment or aquifer parameters. The results of the modelling scheme are illustrated for three major episodes of multi-annual drought (1975-76; 1988-92; 2011-12). They agree with previous documented analyses of the groundwater droughts while providing for the first time a systematic, spatially coherent characterisation of the events. The scheme is amenable to use in near real time to provide short term forecasts of groundwater drought status if suitable forecasts of the driving meteorology are available.

    更新日期:2018-07-08
  • Development of Non-Parametric Evolutionary Algorithm for Predicting Soil Moisture Dynamics
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-04
    Yongchul Shin, Binayak P. Mohanty, Amor V.M. Ines

    Prediction of soil moisture is critical for water resources management. With Global Precipitation Measurement (GPM) and Soil Moisture Active Passive (SMAP) satellites by NASA, spatio-temporal interrelation between rainfall and soil moisture fields (at different extents) will be of great value for satellite product calibration/validation and other hydrologic science investigations. In this study, we explored a non-parametric evolutionary algorithm for prediction of soil moisture from a time series of spatially-distributed rainfall across multiple weather locations under two different hydro-climatic regions. A new genetic algorithm-based hidden Markov model (HMMGA) was developed to estimate long-term soil moisture dynamics at different soil depths using precipitation data as a proxy. Also, we tested transposability of our approach across time under different climatic conditions. To test the new approach, we selected two different soil moisture fields, Oklahoma (130 km × 130 km) and Illinois (300 km × 500 km), during 1995 to 2009 and 1994 to 2010, respectively. We found that the newly developed framework performed well in predicting soil moisture dynamics at different spatial extents. Although our approach has limitations in predicting daily values, it estimates well the weekly soil moisture across the spatial and temporal domains with predictable uncertainties. Furthermore, this approach could provide advantages for good transposability under different weather conditions compared to those of physically-based hydrological models. Overall, our suggested approach could predict weekly soil moisture estimates with precipitation and soil moisture histories and showed the potential of transposability under different weather and land surface conditions. Since the proposed algorithm requires only precipitation (and historical soil moisture data) from existing, established weather stations, it can serve an attractive alternative that can forecast soil moisture using climate change scenarios.

    更新日期:2018-07-05
  • Groundwater dynamics at the hillslope – riparian interface in a year with extreme winter rainfall
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-03
    B. Scheliga, D. Tetzlaff, G. Nuetzmann, C. Soulsby

    Water movement in hillslopes is determined by the subsurface characteristics that control flow paths connecting precipitation to stream flow generation. The hydrological response of hillslopes is notoriously non-linear and non-stationary; with the relative importance of vertical and lateral flow paths also depending on event characteristics and antecedent conditions. In northern boreal regions, climate change projections indicate that wetter and warmer winter conditions are likely to generate more extreme flood events. Here, we report a study from an upland catchment in northern Scotland where a monitoring year provided an opportunity to contextualise observations during the hillslope response to a winter rainfall event that locally caused the most extreme flooding for over 200 years. Monitoring the hillslope water table, soil moisture and isotopes in precipitation, groundwater and stream flow provided invaluable insight into hillslope – riparian coupling. Groundwater with a shallow water table (<0.05 m deep) in poorly drained valley bottom drift deposits maintained almost fully saturated and stream-connected peat soil profiles in riparian areas. In the wettest periods, the groundwater beneath the peat was artesian. On steeper hillslopes, soils were drier and the water table was generally deeper (0.5 to 1 m below ground level), though the profile could fully saturate and groundwater levels reach the surface during the wettest period. Groundwater in deeper wells typically showed an anti-clockwise hysteresis compared to stream flow, and peak levels typically lagged behind the stream by a few hours in the valley bottom and >1 day in the upper hillslope. In contrast, shallower wells in the soil profiles in the riparian area showed more a responsive perched groundwater system with transmissivity feedback in the upper soil layers resulting in much more rapid responses which generally peaked before the stream and exhibited clockwise hysteresis. Analysis of stable isotopes in precipitation, groundwater and streamflow, indicated that groundwater was remarkably well mixed with limited fractionation effects, inferring precipitation on the upper, unconfined hillslopes was the dominant source of recharge - particularly during the winter. The study shows that groundwater plays two roles in generating stream flow: a constant baseflow supply to the stream and time varying-exfiltration into the edge of the riparian zone, which contributes to surface runoff during storm events.

    更新日期:2018-07-04
  • Building socio-hydrological resilient cities against flash floods: Key challenges and a practical plan for arid regions
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-03
    Finlay Horn, Nadir Ahmed Elagib

    The objective of this research is to improve the understanding and recognition of the management challenges to flash flooding hazards and the potential adaptive measures within the arid urban areas through a socio-hydrological framework. Considering the capital of Sudan, Khartoum, as an example of urban arid areas with increasing flash flood risk, the analysis was founded on expert views and opinions collected from a range of different flood management actors following the 2013 and 2014 flash flood events. The qualitative research methods included participant observation, expert interviews and focus groups. The main themes of management challenges recorded included weak institutional capacity, bad governance, limited resources, and poor urban planning. These four themes, in turn, include different types of challenges, among which civil society engagement and lack of coordination of actors, political will, data and tools, and urban development strategy shared the highest number of comments from the professional actors in each theme, respectively. These findings presented a management perspective to the lessons previously established and learned from an impact assessment. Accordingly, the amalgamation of all the lessons learned from the flood research findings enabled a suitable Master Flash Flood Management Plan (MaFFMaP) to be proposed as a final product. This plan would operate within an Integrated Flash Flood Management (IFFM) framework. The facets of the MaFFMaP include steps toward improving the quantity and quality of data resources regarding this hazard, aspects for use of these new datasets within a mixed-measure (structural and non-structural) approach from the authorities, and programmes for building community and civil society capacity through improving awareness and engagement. Furthermore, it is intended that this plan would be a replicable design, which could therefore be adopted and implemented in the wider context of the urban arid regions.

    更新日期:2018-07-04
  • Characterization of horizontal transmissivity anisotropy using cross-hole slug tests
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-03
    Xiaoguang Wang, Hervé Jourde, Mohammed Aliouache, Gérard Massonnat

    Traditional methods for characterizing horizontally anisotropic aquifers are all based on pumping tests. In this paper, we present a new method for the identification of horizontal anisotropy using cross-hole slug tests, which is much more easily accessible comparing to pumping tests. Through scaler transform, an anisotropic medium was converted into an equivalent isotropic medium. When applying the analytical solutions derived for isotropic media to interpret cross-hole slug tests performed in anisotropic media, the estimated transmissivity is the geometrical mean of the anisotropic transmissivity tensor, regardless of sampling direction. However, the apparent storativity calculated from different observation wells, is equal to the true storativity scaled by a factor defined by the formation anisotropy. Thus, anisotropy can be resolved through apparent storativity that bears directional information. The proposed method was first validated by a numerical experiment and then applied to field data. It was found that the tensor results obtained by this new method with cross-hole slug tests are consistent with that obtained by applying the classical Papadopulos’ method with cross-hole pumping tests conducted in the same wells. When applied to heterogeneous media, tensor results produced by the new method may be subject to considerable errors. This is because the results are strongly sensitive to the connectivity between measurement boreholes and the formation medium. To reduce the error level, responses from a large number of observation wells located in various directions around the source well are needed. In addition to the adopted KGS solution for confined aquifers, the proposed methodology can be applied to incorporate other analytical methods for a variety of aquifer types, as long as the characteristic relationship between the measure scale and the aquifer storativity can be established.

    更新日期:2018-07-04
  • Rooting depth controls potential groundwater recharge on hillslopes
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-03
    Han Li, Bingcheng Si, Min Li

    Land use changes may modify ecohydrological processes in soil, altering groundwater quantity and quality in arid and semi-arid regions. The effects of land use change were well documented on flatlands, but the effect of rooting depth on groundwater recharge is poorly understood. This study is to evaluate how conversion of shallow-rooted to deep-rooted vegetation affects groundwater recharge at different landscape positions (i.e. tableland, upslope, midslope, and downslope). Two adjacent transects were selected for a paired plot design: one was covered with shallow-rooted perennial grasses and the other was planted with deep-rooted apple trees or apricot trees in 1990’s. Soil cores (as deep as 13 to 25 m) were collected at each of the four landscape positions along the two transects for the determination of soil water contents, root distributions, and soil tritium contents. Groundwater recharge rates beneath shallow-rooted vegetation were determined from the tritium peak method, and that beneath deep-rooted vegetation were calculated by subtracting the annual soil water deficit from recharge rates beneath shallow-rooted vegetation. Results show that, there is no significant difference in groundwater recharge between the four landscape positions under shallow-rooted vegetation (p > 0.05); however, there is a substantial difference between different slope positions along the other transect (p < 0.05). Cross comparison between the two transects show that conversion from the shallow-rooted to deep-rooted vegetation resulted in a significant reduction of groundwater recharge (p < 0.05) which reduced to virtually zero when the rooting depth is deeper than 15 m. Therefore, we conclude that rooting depth is a major control of groundwater recharge. This study is the first attempt to evaluate the effect of deep-rooted vegetation in the deep unsaturated zone on groundwater recharge on hillslopes with terraces, having important implications to afforestation and to understanding ecohydrological processes in natural ecosystems.

    更新日期:2018-07-04
  • Bisphenol A in the Yellow River: Sorption Characteristics and Influential Factors
    J. Hydrol. (IF 3.727) Pub Date : 2018-07-02
    Yufeng Jiang, Longmiao Yuan, Lanlan Liu, Leiping Shi, A-long Guang, Zhongfeng Mu

    Sorption is an important means for pollutant migration in aquatic environments and an important mechanism of pollutant transfer and transformation. Thus, understanding the sorption/desorption of organic pollutants in an aquatic environment is vital to predicting pollutant fate. In this study, Bisphenol A (BPA) was selected as the target pollutant for an investigation of sorption characteristics on three sediments in the Lanzhou section of the Yellow River, with examination of sorption thermodynamic parameters and the effects of temperature, pH, and sediment particle size. Sorption is described well by the pseudo-second-order kinetic model, occurring at two stages, fast (0–6 h) and slow (6–16 h), with equilibrium reached within 16 h. The results suggested that the intraparticle diffusion was dominant in the sorption process. Sorption thermodynamics was nonlinear, fitting well with the Freundlich isotherm model. Physical sorption is the likely mechanism, combining the contributions of π–π interaction and hydrophobic interaction. Thermodynamic parameter analysis showed that Gibbs free energy, enthalpy, and entropy were less than zero, showing that it is spontaneous, exothermic, and chaos-decreasing. Among tested influence parameters, pH values, ionic strengths, temperatures, and particle sizes were found to considerably influence the sorption of BPA. Sorption capacity decreased as sediment particle size increased and as pH increased. Sorption capacity increased with increasing Ca2+ and decreased with increasing Na+. The results have important implications regarding the impact of sorption/desorption at different environmental factors and fate of BPA in Yellow River.

    更新日期:2018-07-02
  • Geochemical Characterization and Modeling of Regional Groundwater Contributing to the Verde River, Arizona Between Mormon Pocket and the USGS Clarkdale Gage
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-30
    Kimberly Beisner, W. Payton Gardner, Andrew G. Hunt

    We use synoptic surveys of stream discharge, stable isotopes, and dissolved noble gases to identify the source of groundwater discharge to the Verde River in central Arizona. The Verde River more than doubles in discharge in Mormon Pocket over a 1.4 km distance that includes three discrete locations of visible spring input to the river and other diffuse groundwater inputs. A detailed study of the Verde River between Mormon Pocket and the USGS Clarkdale Gage was conducted to better constrain the location of groundwater inputs, the geochemical signature and constrain the source of groundwater input. Discharge, water quality parameters (temperature, pH, specific conductance, and dissolved oxygen), stable isotopes (δ18O and δ2H), noble gases (He, Ne, Ar, Kr and Xe), and radon (222Rn) from river water were collected. Groundwater samples from springs and wells in the area were collected and analyzed for tracers measured in the stream along with some additional analytes (major ions, strontium isotopes (87Sr/86Sr), carbon-14, δ13C, and tritium). Groundwater isotopic signature is consistent with a regional groundwater source. Groundwater springs discharging to the river have a depleted stable isotopic signature indicating recharge source up to 1000 m higher than the discharge location in the Verde River and are significantly fresher than stream water. Spring water has a radiocarbon age of several thousand years and some areas have tritium less than the laboratory reporting level or low concentrations of tritium (1.5 TU). The strontium isotopes indicate groundwater interaction with tertiary volcanic rock and Paleozoic sedimentary rocks. Along the study reach with distance downstream, Verde stream water chemistry shows increased 222Rn, freshening, increased 4He, and isotopic depletion with distance downstream. We estimated total groundwater discharge by inverting a stream transport model against 222Rn and discharge measured in the stream. The salinity, 4He, and stable isotope composition of discharging groundwater was then estimated by fitting modeled values to observed in-stream values. Estimated groundwater inflow to the stream was well within the ranges observed in springs, indicating that the main source of streamflow is deep, regional groundwater. These results show that synoptic surveys of environmental tracers in streams can be used to estimate the isotopic composition and constrain the source of groundwater discharging to streams. Our data provide direct field evidence that deep, regional groundwater discharge can be a significant source of streamflow generation in arid, topographically complex watersheds.

    更新日期:2018-07-01
  • Ecohydrological effects of biological soil crust on the vegetation dynamics of restoration in a dryland ecosystem
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-30
    Ning Chen, Xinping Wang, Yafeng Zhang, Kailiang Yu, Changming Zhao
    更新日期:2018-07-01
  • A spatial downscaling approach for the SMAP passive surface soil moisture product using random forest regression
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-30
    Wei Zhao, Nilda Sánchez, Hui Lu, Ainong Li

    The low-resolution characteristic of passive microwave surface soil moisture (SSM) products greatly limits their application in many fields at regional or local scale. Aiming to overcome this limitation, a random forest (RF)-based downscaling approach was proposed in this study to disaggregate the Soil Moisture Active and Passive (SMAP) SSM product with the synergistic use of the Optical/Thermal infrared (TIR) observations from the Moderate-Resolution Imaging Spectro-radiometer (MODIS) onboard the Terra and Aqua satellites. The Iberian Peninsula was selected as the study area during the period from 2015 to 2016.First, the performance of the RF-based approach in building the SSM relationship model with surface variables (surface temperature, vegetation index, leaf area index, albedo, water index, solar factor, and elevation) was compared with that resulting from a widely used polynomial-based relationship model. Good agreement was achieved for the RF-based method with a correlation coefficient (R) above 0.95 and a mean root-mean-square deviation (RMSD) of 0.009 m3/m3.Next, four data combinations (AM+Terra, AM+Aqua, PM+Terra, and PM+Aqua) were generated according to the different overpass times of the SMAP and MODIS observations, and they were separately used to derive the spatially downscaled SSM with the proposed RF-based downscaling method. Validation was performed with the in situ measurements from the REMEDHUS network of the University of Salamanca in Spain. The results indicated that all combinations have similar good performances with an unbiased root-mean-square difference (ubRMSD) of 0.022 m3/m3, and the downscaled SSM at 1-km spatial resolution presented better accuracy while showing higher spatial heterogeneity and more detailed temporal pattern.Finally, the temporal changing pattern of the downscaled SSM was assessed with the precipitation time series from eight meteorological stations in the study area, and the rainfall effect on the variation of SSM was well tracked from its temporal changes.Overall, this study suggests that the proposed RF-based downscaling method is able to capture the variation of SSM well, and it should be helpful to improve the resolution of passive microwave soil moisture data and facilitate their applications at small scales.

    更新日期:2018-07-01
  • Stochastic generation of daily rainfall events: A single-site rainfall model with Copula-based joint simulation of rainfall characteristics and classification and simulation of rainfall patterns
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-30
    Chao Gao, Yue-Ping Xu, Qian Zhu, Zhixu Bai, Li Liu

    Rainfall event simulation can be very useful in many hydrological and hydraulic practices such as dam design. The aim of this study is to propose a new single-site stochastic model for generating daily rainfall events. The model has two components: Copula-based joint simulation of rainfall characteristics and rainfall temporal pattern simulation. Compared with prevailing stochastic rainfall models, this new model can not only preserve the dependence relationship between rainfall duration and rainfall depth by using Copula functions, but also take different temporal rainfall patterns that can cause various hydrological responses of watersheds into consideration. Additionally, the internal clustering validation index is introduced in this study to objectively determine the number of representative rainfall patterns in this model. Lastly, a framework is designed to apply the developed stochastic model to 39 gauged meteorological stations in Zhejiang Province, East China and to extend its application to one ungauged site for validation. The final validation results were sound and indicated that the developed stochastic model is robust and can be applied at both gauged stations and ungauged sites for generating long rainfall records.

    更新日期:2018-07-01
  • Modelling of River Faecal Indicator Bacteria Dynamics as a Basis for Faecal Contamination Reduction
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-30
    M.M. Majedul Islam, Ekaterina Sokolova, Nynke Hofstra

    To improve microbial water quality and to prevent waterborne disease outbreaks, knowledge on the fate and transport of contaminants and on the contributions from different faecal sources to the total contamination is essential. The fate and transport of faecal indicators E. coli and enterococci within the Betna River in Bangladesh were simulated using a coupled hydrodynamic and water quality model. The hydrodynamic model for the river was set up, calibrated and validated with water level and discharge in our earlier study. In this study, the hydrodynamic model was further validated using measured water temperature and salinity and coupled with the water quality module. Bacterial load data from various faecal sources were collected and used as input in the water quality model. The model output corresponded very well with the measured E. coli and enterococci concentrations in the river; the Root Mean Square Error and the Nash-Sutcliffe efficiency for Log10-transformed concentrations were found to be 0.23 (Log10 CFU/100 ml) and 0.84 for E. coli, and 0.19 (Log10 CFU/100 ml) and 0.86 for enterococci, respectively. Then, the sensitivity of the model was tested by removing one process or forcing at a time. These simulations revealed that the microbial decay, the upstream concentrations and the discharge of untreated wastewater were the primary factors controlling the concentrations in the river, while wind and the contribution from the diffuse sources (i.e. urban and agricultural runoff) were unlikely to have a major influence. Finally, the model was applied to investigate the influence of wastewater treatment on the bacteria concentrations. This revealed that wastewater treatment would result in a considerable improvement of the microbial water quality of the Betna River. This paper demonstrates the application of a comprehensive state-of-art model in a river in a data-poor tropical area. The model can potentially be applied to other watersheds and can help in formulating solutions to improve the microbial water quality.

    更新日期:2018-07-01
  • Design of Sponge City: lessons learnt from an ancient drainage system in Ganzhou, China
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-28
    Ye-Shuang Xu, Shui-Long Shen, Yue Lai, An-Nan Zhou

    This paper presents a case study on an ancient drainage system in the Hetao old urban center, Ganzhou, China, which is playing a key role in the prevention of urban flooding. The system includes ancient city walls, a Fushou ditch, and ponds. The ancient city walls were constructed to defend the river water intrusion. The Fushou ditch and ponds primarily served for the drainage and storage of the rainwater, respectively. The process of rainwater management in the Ganzhou ancient drainage system, including the guidance, storage, infiltration, purification and utilization, and drainage of rainwater, confirms the feasibility of the design concept of modern sponge city. Based on the lessons learnt from this ancient drainage system, the guideline for the rainwater management and design of Sponge City is proposed. It is suggested that the sponge city should be planned before the new urban development. During the construction of sponge city, the dispersed ponds and the ditches made of durable and permeable materials in Ganzhou ancient drainage system are recommended to increase the amount of infiltration, storage and utilization of rainwater.

    更新日期:2018-06-30
  • Landscape and Anthropogenic Factors Affecting Spatial Patterns of Water Quality Trends in a Large River basin, South Korea
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-28
    Janardan Mainali, Heejun Chang

    Understanding changes in water quality over time and landscape and anthropogenic factors affecting them are of paramount importance to human and ecosystem health. We analyzed the seasonal trends of total nitrogen, total phosphorus, chemical oxygen demand, and total suspended solid (SS) in the Han River Basin (HRB) of South Korea using the Mann-Kendall test. We explored the effects of anthropogenic (land cover and population) and natural factors (topography and soil) on the trends by using Moran's Eigenvector based spatial filtering regressions at four different spatial scales. Water quality of the HRB generally improved from the early 1990s to 2016 with decreasing summer nutrient and winter SS concentrations. Water quality trends were spatially autocorrelated with distinct spatial variations within the basin. Some stations close to the Seoul metropolitan area, however, still exhibited poor water quality conditions. Approximately 20 to 70 percent of spatial variation of different water quality trends were explained by some combination of current agricultural land cover, forest land cover, % area covered by water, change in those land covers and slope variations. The 100 meter buffer and one-kilometer upstream scale analyses generally showed higher explanatory power than the sub-watershed scale analyses, while the effect of seasons differed for different parameters. The significant factors in each regression model typically differed among different scales but not among different seasons of the same scale. The spatial filtering approach removed the residual spatial autocorrelation and thus significantly increased the explanatory power of water quality trend models.

    更新日期:2018-06-30
  • Switching the Richards’ equation for modeling soil water movement under unfavorable conditions
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-27
    Jicai Zeng, Yuanyuan Zha, Jinzhong Yang

    Simulation of variably saturated soil water flow requires the use of pressure head, or soil moisture, or a switching between the two, as the primary variable for solving Richards’ equation. Under unfavorable conditions, such as heterogeneity, rapidly changing atmospheric boundary, or sudden infiltration into dry soils, the traditional non-switching method suffers from numerical difficulties. Solving this problem with a primary variable switching method is less preferred due to the mathematical complexity. While the Picard method is more popular for solving the non-switching models due to its simplicity and stability, two different forms of Richards’ equation are combined into one numerical scheme for switching under specific hydraulic conditions. The method is successfully implemented in a one-dimensional model solved by a Picard iteration scheme. A threshold saturation based on the soil moisture retention relation is used for switching between either form of the Richards’ equation. The method developed here is applicable for simulating variably saturated subsurface flow in heterogeneous soils. Compared with traditional methods, the proposed model conserves mass well and is numerically more stable and efficient.

    更新日期:2018-06-28
  • Effects of dynamic land use inputs on improvement of SWAT model performance and uncertainty analysis of outputs
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-27
    Qingrui Wang, Ruimin Liu, Cong Men, Lijia Guo, Yuexi Miao

    The objective of this study was to evaluate the impacts of static and dynamic land use input conditions on the performance of non-point source (NPS) model and find out whether dynamic land use input can improve the model accuracy. Soil and Water Assessment Tool (SWAT) model was selected as the evaluation model and seven different land use input conditions were set by setting the land use update file in SWAT. The results showed that the land use pattern in the study area changed from 2000 to 2015 due to climate change and human activities, leading to inconsistencies between different land use patterns. The calibrated results indicated that dynamic land use input conditions could apparently improve the simulation accuracy of total nitrogen (TN) and total phosphorus (TP). CE5Y condition had the best calibrated result with R2R2 and NSE larger than 0.7 and 0.6, respectively. However, for flow simulation, the land use input conditions had no apparent effect on the model calibration and validation results. The deviation analysis of the model outputs indicated that monthly outputs were more affected by the land use input conditions than annual outputs and that deviations in wet seasons were larger than those in normal and dry seasons. The highest MAD occurred in June and August with a value of 82.87 t and 1.56 t for TN and TP, respectively. This study revealed the importance to consider the land use change when simulating the NPS pollution, and could provide support for land use input settings of NPS pollution models.

    更新日期:2018-06-28
  • Temporal streamflow analysis: Coupling nonlinear dynamics with complex networks
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-27
    Nazly Yasmin, Bellie Sivakumar

    This study presents a new approach for complex networks-based analysis of temporal streamflow dynamics. The novelty comes in the form of using nonlinear dynamic concepts to construct the temporal streamflow network. The approach involves three steps. First, the single-variable streamflow time series is represented in a multi-dimensional phase space using delay embedding, i.e. phase space reconstruction. Next, this reconstructed phase space is treated as a network, with the reconstructed vectors (instead of the streamflow values themselves) serving as the nodes and the connections between them serving as the links. Finally, the strength of each node in the network is determined using a distance metric. The approach is employed independently to monthly streamflow time series observed over a period of 53 years (January 1950–December 2002) from each of 639 stations in the contiguous United States. For each time series, different delay time values for phase space reconstruction are considered and the optimum embedding dimension is determined using the false nearest neighbor (FNN) method. The results indicate the usefulness of the phase space reconstruction-based network construction for examining the temporal connections in streamflow. The distribution of the strengths of nodes for any streamflow network is used to identify the type of the underlying network. The average node strength of each of the 639 streamflow networks are also interpreted: (1) to identify similarities and differences between the stations; (2) to explain the role of catchment and flow properties (drainage area, elevation, and flow mean) on network strength; and (3) to assess the influence of time (i.e. month of the year) on network strength.

    更新日期:2018-06-28
  • Global Intercomparison and Regional Evaluation of GPM IMERG Version-03, Version-04 and its latest Version-05 Precipitation Products: Similarity, Difference and Improvements
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-27
    Cunguang Wang, Guoqiang Tang, Zhongying Han, Xiaolin Guo, Yang Hong

    The overarching goal of this study is to intercompare the newly released Integrated Multi-satellitE Retrievals for GPM (IMERG) Version 05 (V05) products with its former Version 04 (V04) and Version 03 (V03) products and also assess any differences and improvements, with cross-evaluation against the Global Precipitation Climatology Project (GPCP) Version 2.3, Multi-Source Weighted-Ensemble Precipitation (MSWEP) Version 2.1 and the dense gauge networks in China. Firstly, the gauge-adjusted products (Final run) of V03, V04 and V05 are compared over the globe. Then, the near-real-time products without gauge adjustments (Early and Late run) and Final run products of all versions are evaluated against ground-based observations comprised of more than 30000 gauges over Mainland China at 0.1° × 0.1° grid and hourly and daily temporal scales. The primary conclusions are: (1) globally, both V04 and V05 Final run show significant differences and improvements from V03. Particularly, the overall mean oceanic precipitation of V04 and V05 increases by +31.36% and +28.81% respectively from that of V03 and much closer to GPCP and MSWEP; (2) over Mainland China, the Early and Late run products of the same version (V03 or V04) generally have similar performance, while V04 Early and Late run have better performance in most regions than the corresponding run of V03 except in the arid Xinjiang Province and the mountainous Tibetan Plateau; and (3) V04 and V03 Final run show comparable performance, while V05 Final run generally improves upon both V04 and V03 and has the best performance among the seven standard IMERG products. The improvement of V05 Final run is particularly evident in southeastern and western China. At a timely matter, the study provides first-hand global and regional assessment feedback to IMERG algorithm developers and also sheds insights for GPM precipitation product users across the world.

    更新日期:2018-06-28
  • Accounting public and individual flood protection measures in damage assessment: A novel approach for quantitative assessment of vulnerability and flood risk associated with local engineering adaptation options
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-28
    Balqis M. Rehan

    A typical engineered flood protection for a community exposed to fluvial flooding is constructions of flood defense dedicated for public-wide protection. Over the past few years, there have been efforts to mainstreaming individual precautionary measures as to reduce risk of flooding. Consideration of individual protection measures alongside public protection measures is mainly to increase resistance of local communities to flood impacts whilst deliberating the spatial constraints of public protection measures and optimizing cost of adaptation. However, quantification of vulnerability and risk reduction of combined public and individual protection measures has not received much attention, far less a risk-based economic analysis. In assisting flood risk management decision making, a systematic approach to quantify vulnerability and flood risk of conditions with the combined protection measures is deemed crucial. This study proposes a methodology to assess vulnerability and flood risk of flooding considering combined public and individual protection measures, aiming for relevant applications in economic appraisal of local protection options. The applicability of the methodology is demonstrated using a case study of a residential area of Teddington near the Greater London. A range of different possible levels of protection was also included to exemplify the usefulness of the methodology in search for an optimal protection level. The results show that the combined public and individual protection can reduce flood risk significantly. The study highlights that the methodology can serve as a tool for a practical and manageable vulnerability and flood risk assessment.

    更新日期:2018-06-28
  • Global River Slope: A New Geospatial Dataset and Global-scale Analysis
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-28
    Sagy Cohen, Tong Wan, Md Tazmul Islam, J.P.M. Syvitski

    A rivers’ longitudinal gradient (i.e. slope) is a key parameter in fluvial hydrology, hydraulics, and geomorphology. It affects a multitude of fluvial variables such as flow velocity and sediment transport. Limitations in river slope data, both its availability and accuracy, constrain the fidelity of fluvial modeling, particularly at larger or global scales. Traditional slope calculation algorithms cannot accurately predict river slopes as these are based on cell-by-cell calculation, which is only suitable for hillslopes and small mountainous streams. This paper presents a methodology for calculating global river slope and a procedure to upscale it for relatively coarse resolution, suitable for global scale modeling. The methodology is based on a simple principle of calculating slope from elevation depression over the length of a river segment, which is automated to allow global scale calculations. Version 1.0 of the Global River-Slope (GloRS) geospatial dataset is introduced and shown to be a step improvement over a previous product (NHDplus for the contiguous United States) and compares favorably to observed slope data collected from the literature. Statistical analysis of Earth’s continents and large basins highlights interesting spatial trends. A semi-empirical regression analysis between basin-average river slope and other basin-scale parameters show that terrain slope accounts for 67% of the variability in basin-average river slope, with average discharge, sediment load and basin temperature contributing additional improvements to global predictions of 3%, 4%, and 3%, respectively.

    更新日期:2018-06-28
  • The response of crop water productivity to climatic variation in the upper-middle reaches of the Heihe River basin, Northwest China
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-28
    Jun Niu, Qi Liu, Shaozhong Kang, Xiaotao Zhang

    The Heihe River basin is one of the important bases for commercial grain production in China. The climate change impacts on crop yield and crop water productivity (CWP) need to be examined for sustainable development of regional agriculture, especially under the pressure of population growth and regional water scarcity. A distributed hydrological model was constructed for the upper-middle reaches of the Heihe River basin on the basis of the Soil and Water Assessment Model (SWAT). The sensitivity ranks of hydrological parameters were evaluated for the runoff and evapotranspiration processes, and then independently calibrated with the observations of three gauging stations (Qilian, Zhamashike, and Yingluoxia stations) and the evapotranspiration data derived by remote-sensing. The study first simulated crop yield and CWP for four typical crop types, namely corn, spring wheat, spring barley, and spring canola-Polish, for the period of 1966-2014 using the SWAT model, calibrated with the crop yield data (during the period of 2005-2014) from Zhangye Statistics Yearbook. The spatial-temporal features of crop yield and CWP were analyzed. A fluctuating growth was found for the 49 year trend of corn, spring wheat, and spring canola-Polish. The spring barley shows a slightly decreasing trend. The high-yield area moved from the west part (Suzhou and Gaotai counties) to the east part (Linze, Ganzhou, and Shandan counties) of the basin for the past 49 years, and the area of high CWP concentrated in the Gaotai and Linze Counties. The responses of CWP to climatic forcing were further studied using wavelet coherence method. It is found that maximum temperature dominated the CWP evolutions, especially at the long-term scales. The corn showed the largest elastic responses to the climatic factors, which may be favorable to improve regional CWP by expanding planting area. In addition, the strategies of regional CWP improvement were discussed based on the results.

    更新日期:2018-06-28
  • Agricultural economic losses caused by protection of the ecological basic flow of rivers
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-26
    Bo Cheng, Huaien Li

    Equitable distribution of agricultural and ecological water is a great challenge, which has important implications for food safety, with models required to calculate agricultural economic losses caused through protection of the ecological basic flow of rivers. A new model has been used to calculate agricultural economic losses caused by river ecological basic flow in the Baoji Section of the Weihe River, which is the largest tributary of the Yellow River, China. Results show that agricultural economic losses were negatively correlated to high levels of water runoff, with the agricultural water sector often unable to safeguard river ecological basic flow systems when annual food safety guarantee levels of 400kg per person were met. Water-saving measures could be used to help protect river ecological basic flow, based on policies of agricultural ecological compensation, water rights transactions and encouraging the public to employ appropriate water-saving measures. However, whilst recommendations from this study enabled the agricultural water department to decrease economic losses and improve food safety guarantee levels, they could not provide full protection of river ecological basic flow.

    更新日期:2018-06-27
  • 更新日期:2018-06-27
  • How reliable are satellite precipitation estimates for driving hydrological models: a verification study over the mediterranean area
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-26
    S. Camici, L. Ciabatta, C. Massari, L. Brocca

    Satellite-based rainfall products (SRPs) are nowadays available at ever increasing accuracy and higher spatial and temporal resolution with respect to the past. Despite this, they are scarcely used in hydrological modeling. The main reasons may be related to: 1) the large bias characterizing satellite precipitation estimates, which is dependent on rainfall intensity and the season, 2) the relatively large spatial/temporal resolution with respect to the applications, 3) the timeliness, which is often insufficient for operational purposes, and 4) a general (often not justified) skepticism of the hydrological community in the use of satellite products for land applications.The objective of this study is to explore the feasibility of using SRPs to force a lumped hydrologic model – MISDc – over 15 basins in the Mediterranean area with different sizes and physiographic characteristics. Specifically, TMPA 3B42-RT, CMORPH, PERSIANN and a new soil moisture-derived rainfall datasets, SM2RAINCCI, obtained through the application of SM2RAIN algorithm (Brocca et al., 2014) to ESA CCI soil moisture product are used in the analysis. The performances obtained with the selected SRPs are compared with those obtained from a ground-based rainfall product (E-OBS). In addition, the performance obtained by an integration of the SRPs is investigated to see whether merged rainfall observations are able to improve flood simulations.The results highlight that SRPs provide relatively low performances when used to force MISDc model with respect to the case where ground observations are used. Worst results are obtained in smaller basins (<500 km2) that, however, represent the main target for flood modelling in the Mediterranean area. Relatively better performances are obtained when independent SRPs are integrated each other, and particularly for the case where TMPA 3B42-RT is integrated with SM2RAINCCI. In accordance with previous studies, this suggests that the exploitation (via integration) of independent sources of rainfall offers a potential way to reduce rainfall-induced streamflow errors, even in challenging areas like the Mediterranean.

    更新日期:2018-06-27
  • Response to “Comment on the paper Scale dependent solute dispersion with linear isotherm in heterogeneous medium (Journal of Hydrology 520 (2015) 289-299)”
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-26
    Mritunjay Kumar Singh, Pintu Das

    Transformation plays a significant role in solving hydrological problems. In response to the comment on Singh and Das (2015) by Deng et al., regarding the transformation, boundary conditions and subsequent analytical solution of advection dispersion equation in semi-infinite heterogeneous porous media, it is argued that the transformation used by Singh and Das (2015) for finding the analytical solution is correct and mathematically valid. Also, the different expression of f(mt)f(mt) used to obtain the solution are explained with their physical relevance in the field.

    更新日期:2018-06-27
  • Quantifying the roles of single stations within homogeneous regions using complex network analysis
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-23
    A. Agarwal, N. Marwan, R. Maheswaran, B. Merz, J Kurths

    Regionalization and pooling stations to form homogeneous regions or communities are essential for reliable parameter transfer, prediction in ungauged basins, and estimation of missing information. Over the years, several clustering methods have been proposed for regional analysis. Most of these methods are able to quantify the study region in terms of homogeneity but fail to provide microscopic information about the interaction between communities, as well as about each station within the communities. We propose a complex network-based approach to extract this valuable information and demonstrate the potential of our approach using a rainfall network constructed from the Indian gridded daily precipitation data. The communities were identified using the network-theoretical community detection algorithm for maximizing the modularity. Further, the grid points (nodes) were classified into universal roles according to their pattern of within- and between-community connections. The method thus yields zoomed-in details of individual rainfall grids within each community.

    更新日期:2018-06-25
  • Hysteresis in Hydrology and Hydrological Modeling: Memory, Path-Dependency, or Missing Physics?
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-23
    S. Gharari, S. Razavi

    Hysteresis is a widely reported phenomenon in natural and engineered systems across different temporal and spatial scales. Its definition is non-unique and rather context-dependent, while systems with hysteretic behavior, including hydrological systems, are commonly referred to as path-dependent systems or systems with memory. Despite widespread existence of hysteretic processes, the current generation of hydrologic models do not directly account for hysteresis. In this paper, we review the fundamentals, theories, and general properties of hysteresis in the broad scientific literature and then focus on its representations in hydrological sciences. Through illustrative examples, we show how an incomplete understanding or representation of the underlying processes in a system can lead to considering the system as path-dependent. We argue that, in most cases, hysteresis is a manifestation of our dimensionality-reducing approach to process understanding and representation. We further explain that modelling hysteresis in an ideal world requires a full-dimensional process representation based on a perfect understanding of the processes and their spatio-temporal scale dependency. We discuss, however, that the missing dimensions/physics in a hydrologic model may be compensated to some extent by enabling the model with formal hysteretic components and also that the conventional model structure and parametrization may be designed in a way to partially reproduce a desired hysteretic behavior.

    更新日期:2018-06-25
  • A new efficient Bayesian parameter inference strategy: application to flow and pesticide transport through unsaturated porous media
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-23
    Anis Younes, Thierry.A. Mara, Marc Voltz, Lamia Guellouz, Husam Musa Baalousha, Marwan Fahs

    Statistical calibration of flow and transport models in unsaturated porous media is often carried out with Markov Chain Monte Carlo (MCMC) methods. However, the practicality of these methods is limited by their computational requirement, particularly when large prior intervals are assigned to the model parameters. In this work, a new operational strategy is investigated to alleviate the computational burden of MCMC samplers using results from a preliminary calibration performed with the First-Order Approximation (FOA) method. With the new strategy, the posterior distribution is approximated using a high-order Polynomial Chaos Expansion (PCE) surrogate model constructed over reduced parameter ranges. The latter are obtained from the 99.9 FOA confidence intervals. Two challenging test cases are investigated to assess efficiency and accuracy of the new strategy. The first test case considers estimation of flow and pesticide transport parameters from a synthetic infiltration experiment. The second test case deals with the assessment of unsaturated hydraulic soil parameters from a real-word laboratory drainage experiment. The results of the proposed strategy are compared to those of FOA, of the standard MCMC method and of an improved MCMC method in which the sampler is preconditioned with draws from the FOA posterior distribution. For both test cases, the new strategy provides accurate mean estimated parameter values and uncertainty regions and is much more efficient than the other MCMC methods. It is up to 50 times more efficient than the standard MCMC method.

    更新日期:2018-06-25
  • A modelling study of rainfall-induced shallow landslide mechanisms under different rainfall characteristics
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-22
    Qihua Ran, Yanyan Hong, Wei Li, Jihui Gao

    Rainfall-induced shallow landslide is a common geological hazard around the world that can pose serious threat to both lives and property. Previous studies suggested that rainfall induced shallow landslides always occurred either above the bottom of a downward wetting front in infiltration, or below a rising water table. This paper proposed a different mechanism of shallow landslides in a modelling approach. The comprehensive physics-based Integrated Hydrology Model (InHM) and the infinite slope stability model were employed on a virtual slope to simulate the hydrologic response and estimate the slope stability. Different failure mechanisms with various characteristics were investigated under diverse rainfall scenarios (i.e., various combinations of rainfall depths, durations and temporal patterns). The results showed a novel mechanism of shallow landslides: a significant vertical change in saturated hydrologic conductivity causes the accumulation of infiltrated water, and subsequently leading to an increase pore pressures and landslides in unsaturated soil layer. More importantly, this kind of landslide would bring larger landslide volume even with smaller total rainfall depths. This study expanded our understanding about landslides and had important application in alleviating the loss of lives and property.

    更新日期:2018-06-22
  • Sequential data-worth analysis coupled with Ensemble Kalman Filter for soil water flow:A real-world case study
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-22
    Yakun Wang, Liangsheng Shi, Yuanyuan Zha, Xiaomeng Li, Qiuru Zhang, Ming Ye

    Given the high cost of data acquisition in soil water problems, it is becoming increasingly essential to collect the measurements as cost-efficient as possible. By introducing the data-worth analysis framework coupled with Ensemble Kalman Filter (EnKF), this real-world case study attempts to assess the worth of potential soil moisture observations before data collection. A field experiment was implemented to demonstrate the feasibility of quantifying the effect of future data on uncertainty reduction under real circumstances in a sequential way. The data worth of future observations is defined regarding soil hydraulic parameter estimation or soil moisture profile retrieval. Four information measures, including the trace (Tr T r ), Shannon entropy difference (SD), relative entropy (RE) and degrees of freedom for signal (DFS), are introduced to quantify the information content. The sequential data worth analysis framework is examined by a number of cases, including under different irrigation intensities, with different prior data (existing observations that have already been collected), and with data of various depths and different measurement errors. We demonstrated the ability, and the challenge as well, of quantifying the data worth sequentially. Our results showed that data worth assessment regarding soil moisture profile retrieval is more difficult than that regarding parameter identification. Variance-type and covariance-type metrics have relatively loose accuracy requirement on potential observations (future possible observations to be collected), while mean-covariance-type metrics require higher accuracy. The vertical covariance of soil moisture is susceptible to the effect of atmospheric boundary condition, which eventually imposes a challenge on the quantification of data worth with covariance involved indices. The match between the expected and reference data worth can be improved by assimilating more prior data. However, more prior data cannot compensate for the damage from possible model structural error due to the changed scenarios between the prior stage and the posterior or preposterior stage. Shallow soil moisture data generally has larger data worth than deep observations in our study, but evaluating data worth with shallow data is subject to considerable uncertainty if covariance-type or mean-covariance-type index is employed. Smaller measurement error does not always lead to improved data worth estimation.

    更新日期:2018-06-22
  • Comparing evapotranspiration characteristics and environmental controls for three agroforestry ecosystems in a subtropical humid karst area
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-22
    Rongfei Zhang, Xianli Xu, Meixian Liu, Yaohua Zhang, Chaohao Xu, Ruzhou Yi, Wei Luo

    Karst landforms account for 10% of the Earths land surface, and it is well-known that water is a limiting factor for karst ecosystems because numerous underground fractures and conduits induce rapid drainage. Therefore, an understanding of ecosystem water consumptions (evapotranspiration) and environmental controls is particularly important for land management on karst landforms. This study compared the actual evapotranspiration (AET) characteristics and analyzed the controls of three agroforestry ecosystems by field observations using a refitted ventilated-chamber, thermal dissipation probes and micro-lysimeters in a subtropical humid karst catchment from 12th March 2015 to 26th May 2016. Results show that: 1) the diurnal transpiration curves of trees plateau at noon with low fluctuations at a high level, while evapotranspiration curves of grass and crop ecosystems present single peaks; 2) AET of the forest-grass mixed ecosystem (7.64 ± 5.75 mm·day-1) was significantly higher than crop (4.24 ± 3.35 mm·day-1) and grass ecosystems (5.78 ± 3.53 mm·day-1); 3) AET of grass and crop ecosystems were most sensitive to temperature, while the forest-grass mixed ecosystem was more sensitive to leaf area index (LAI) than other factors; 4) AET of the forest-grass mixed ecosystem was more sensitive to deep soil moisture (>30 cm), while grass and crop ecosystems were more sensitive to shallow soil moisture (10 cm and 20 cm). This study suggests that soil water content was not key limit factors to AET in humid karst landscapes. However, LAI, which can be controlled by land management, heavily influenced AET rates and E/AET (E, evaporation) ratio through changing water demand.

    更新日期:2018-06-22
  • Comparative Study of 1D entropy-based and conventional deterministic velocity distribution equations for open channel flows
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-19
    Hao Luo, Vijay Singh, Arthur Schmidt

    Velocity distributions for open channel flows have been investigated using deterministic and probabilistic approaches. It is well known that the vertical velocity profiles in wide open channels (aspect ratio width/depth> > 5) can be approximated by logarithmic velocity laws and power laws. Recently the entropy concept in the forms of Shannon entropy and Tsallis entropy has been employed to estimate velocity distributions in open channels with different aspect ratios. The accuracy of conventional velocity equations is highly dependent on their parameters that can only be estimated by empirical or semi-empirical analytical relations which requires either a good knowledge of velocity field and/or physical properties of the channel, such as topographic conditions, sedimentation conditions and boundary roughness. In contrast, the entropy based velocity distributions derived based on the least-biased probability density function (PDF) by treating time-averaged velocities as random variables are resilient regardless of the flow and channel conditions. However, a comparison of the velocity profiles computed using deterministic approaches and probabilistic approaches have not been rigorously conducted. Furthermore, the accuracy and reliability of associated velocity distribution equations have not been tested thoroughly using data sets collected using advanced techniques. This paper presents a comprehensive and comparative study to analyze the distinctions and linkages between four commonly used velocity laws and two entropy-based velocity distributions theoretically and quantitatively using selective laboratory and field measurements available in the literature, considering typical sedimentation and channel hydraulic conditions. Amongst all, Tsallis entropy based velocity distribution developed from a generalized form of informational entropy exhibits universal validity to sediment-laden flows in wide alluvial open channels, and is found to be superior to others to predict velocity profiles in large waterways with unmanageable rough beds.

    更新日期:2018-06-22
  • An embedded VPMM-AD model for riverine transient flow and non-reactive contaminant transports
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-19
    Ratnakar Swain, Bhabagrahi Sahoo, Muthiah Perumal

    Although umpteen studies are available in the hydrologic literature for modeling the contaminant transports under steady flow conditions, similar trend is not seen while modeling this process under unsteady flow conditions and, thereby, limiting their field application for pollution monitoring in semi-gauged rivers. In this study, three simple model variants, namely, VPMM-AD(ΨDc), VPMM-AD(ΦDf) and VPMM-AD(Dc) were developed for unsteady state contaminant routing by tight-coupling the physically-based Variable Parameter McCarthy- Muskingum (VPMM) flow-transport sub-model with the Advection-Dispersion (AD) contaminant-transport sub-model. These model variants were extensively tested under unsteady and steady flow conditions using the numerical experiments, and USGS laboratory and real-world river application datasets considering the popular MIKE11-AD model as the benchmark. The study results revealed the consistent superior performance of the VPMM-AD(ψDc) and VPMM-AD(ΦDf) model variants over the benchmark model. The developed approach is a novel one as it is fully physically-based, free from numerical stability problem as the governing equations are solved iteratively, can work at meso-scale with the same computational space and time-steps in the flow and solute routings compatible with the spatiotemporal scales of observation, very simple to use, and do not compromise with the routing accuracy as encountered in the benchmark hydrodynamic model even with a fully implicit finite difference scheme.

    更新日期:2018-06-22
  • Moraine dam breach and glacial lake outburst flood generation by physical and numerical models
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-19
    Sazeda Begam, Dhrubajyoti Sen, Subhasish Dey

    The areas of glacial lakes in the Himalayas continue to increase alarmingly due to global warming with consequent risk of glacial lake outburst flood (GLOF). The outburst is most common for moraine-dammed lakes as a result of a failure of the dam by overtopping and erosion or piping due to seepage. In the present context, GLOF events, especially for the moraine dam failure process needs to be predicted to assess the drastic and detrimental impacts on the downstream river valley. This study focuses on validating an integrated model for simulating the failure of moraine dam by overtopping and erosion using a coupled numerical simulation model. The proposed numerical methodology is validated with the data from experiments in laboratory scale physical models. The results of the model are compared for both the erosional profiles during collapse of the dam and the resulting outflowing flood hydrograph. The primary finding is that the moraine dam height and the volume of the lake upstream of the dam are the most sensitive parameters influencing the GLOF peak. The model is also applied to the field problem of the Tangjiashan lake outburst and dam failure and shows reasonably good agreement with observations. The validated model is also run for the South Lhonak glacial lake in the Sikkim Himalayas, India to obtain the probable flood hydrograph in case of failure of the moraine dam.

    更新日期:2018-06-22
  • Watershed- to continental-scale influences on winter stormflow in the Southern Blue Ridge Mountains
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-19
    Jacob M. McDonald, David S. Leigh, C. Rhett Jackson

    Spatial and temporal influences on the winter (December-March) stormflow characteristics of fifteen United States Geological Survey (USGS)-gaged watersheds in the Southern Blue Ridge Mountains are identified: (1) watershed-scale differences in geomorphology; (2) continental-scale teleconnections during periods of wetness/dryness (based on the relative amount of winter precipitation over a consistent 20 year dataset); and (3) land cover in the context of soil parent material (e.g., development on alluvium/colluvium). Multiple regression was used to determine how much variance could be explained in five hydrologic variables describing the flashiness of peak flow (three original metrics), total seasonal flashiness (Richards Baker flashiness index), and the ratio of total winter stormflow to total discharge (the stormflow index). Models were constrained to three uncorrelated (|0.65|) variables to prevent overfitting to the dataset. Average-, dry-, and wet-years were subset using the z-scores for winter precipitation derived from the 4 km monthly PRISM (Parameter-elevation Relationships on Independent Slopes Model) dataset, for the period of 1986-2006. Relief, slope, and landscape connectivity explain the majority of explained variance in all five of the hydrologic variables during all time periods. During dry-, average-, and wet-years, atmospheric circulation patterns (i.e., North Atlantic Oscillation and Pacific/North American Pattern) explain more variance than total seasonal precipitation (PRISM), which is not true in the majority of the all-years models. Land cover explains only a small portion of the variance in regional stormflow and only when sub-divided based on soil parent material. Results provide a framework for connecting watershed-scale characteristics to regional- and continental-scale processes.

    更新日期:2018-06-22
  • Evaluation of hydrological utility of IMERG Final Run V05 and TMPA 3B42V7 satellite precipitation products in the Yellow River source region, China
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-20
    Fei Yuan, Bing Wang, Chunxiang Shi, Wei Cui, Chongxu Zhao, Yi Liu, Liliang Ren, Limin Zhang, Yonghua Zhu, Tao Chen, Shanhu Jiang, Xiaoli Yang

    Global satellite precipitation products, such as Tropical Rainfall Measuring Mission (TRMM) and its successor, Global Precipitation Measurement (GPM), have provided hydrologists with a critical precipitation data source for hydrological applications in data-sparse or ungauged basins. This study conducts a comparative analysis on the quality of the TRMM Multi-satellite Precipitation Analysis 3B42V7 and the Integrated Multi-satellite Retrievals for GPM (IMERG) Final Run version 05 precipitation products and their hydrological utilities in the Yellow River source region (YRSR), a mountainous Alpine region in northwestern China, from April 2014 to December 2016. Results indicate that when evaluated against the ground precipitation observations, IMERG generally improves the daily precipitation estimates relative to its predecessor 3B42V7. In addition, and the correlation coefficients (CCs) of IMERG (0.328 and 0.527) are significantly higher at grid and basin scales than those of 3B42V7 (0.287 and 0.458). However, the 3-hourly precipitation estimates from both products poorly correlate with the ground observations at grid and basin scales. By using the grid-based Xinanjiang (GXAJ) hydrological model calibrated with the gauge-based precipitation for daily streamflow simulations, the 3B42V7-driven model run shows acceptable hydrological simulation skill with regard to the Nash-Sutcliffe model efficiency coefficient (NSE = 0.729), whereas IMERG demonstrates improved performance (NSE = 0.810), which is comparable with the gauge-based simulation (NSE = 0.807). Input-specific model recalibration effectively enhances the hydrological performance of both satellite products (NSE = 0.856 for IMERG and NSE = 0.840 for 3B42V7). Additionally, the gauge-benchmarked GXAJ model with 3B42V7 has limited hydrological skill in simulating three historical flood events at 3-hourly time intervals (NSE = -0.070–0.702), while IMERG has a slightly better performance (NSE = 0.266–0.792). Model recalibration also significantly improves the simulations of two out of three flood events, and the NSE skill cores of IMERG (0.581–0.901) and 3B42V7 (-0.795–0.852) are relatively lower than that of the gauge-based simulation (0.753–0.969) but comparable. Overall, the IMERG and 3B43V7 satellite precipitation products can be adopted as reliable precipitation sources for hydrological simulations at daily and sub-daily time scales in the study area, with IMERG better suited than 3B42V7. Considering that the low CC values exist in both IMERG and 3B42V7 products, in particular, at a sub-daily temporal scale, the GPM research community should further improve the calibration algorithms and enhance the quality of IMERG products in YRSR. Performing bias-correction of satellite precipitation products is also necessary for hydrological modelers to effectively improve their hydrological utilities.

    更新日期:2018-06-22
  • An improved gene expression programming model for streamflow forecasting in intermittent streams
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-20
    Ali Danandeh Mehr

    Skilful forecasting of monthly streamflow in intermittent rivers is a challenging task in stochastic hydrology. In this study, genetic algorithm (GA) was combined with gene expression programming (GEP) as a new hybrid model for month ahead streamflow forecasting in an intermittent stream. The hybrid model was named GEP-GA in which sub-expression trees of the best evolved GEP model were rescaled by appropriate weighting coefficients through the use of GA optimizer. Auto-correlation and partial auto-correlation functions of the streamflow records as well as evolutionary search of GEP were used to identify the optimum predictors (i.e., number of lags) for the model. The proposed methodology was demonstrated using monthly streamflow data from the Shavir Creek in Iran. Performance of the GEP-GA was compared to that of classic genetic programming (GP), GEP, multiple linear regression and GEP-linear regression models developed in the present study as the benchmarks. The results showed that the GEP-GA outperforms all the benchmarks and motivated to be used in practice.

    更新日期:2018-06-22
  • Effect of embedded-rock fragments on slope soil erosion during rainfall events under simulated laboratory conditions
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-20
    Tiexiong Gong, Yuanjun Zhu, Ming'an Shao

    Quantifying the role of embedded-rock fragments in soil-water processes on a slope is crucial for the application of rock fragments in soil and water conservation practice. In this study, a laboratory runoff and erosion experiment was conducted in the soils embedded with rock fragments (including five rock fragment content (RC) of 0, 0.1, 0.2, 0.3, and 0.4 kg kg-1) in a metal flume under three slopes (5°, 10° and 15°). Results showed that the mean steady infiltration rate in the soil without rock fragment (NULL) was lower than that in the soils containing rock fragment contents (low rock fragment contents of 0.1-0.2 kg kg-1 and high rock fragment contents of 0.3-0.4 kg kg-1, labeled as LOW and HIGH, respectively) as slope gradient = 5°, but was higher than the latter two soils as slope gradients = 10° and 15°. Initial infiltration rate significantly increased with RC (P<0.05). Runoff discharge was negatively related to RC as slope gradient = 5° and was positively related to it as slope gradients = 10° and 15°. There was a steady sediment concentration (SC) after runoff generated as slope gradient = 5°. Sediment discharge and soil erosion modulus for the treatment of HIGH significantly increased with slope gradient (P < 0.05). Reynolds number (Re) decreased with RC and the other hydraulic parameters of friction coefficient (f), shear stress (τ), and stream power (ω) increase with RC. In general, the embedded-rock fragment in the soil can accelerate soil erosion by changing the ratio of infiltration/runoff, surface roughness, and related hydraulic parameters, especially under higher slope gradients. Our findings suggest that using rock fragments to control soil erosion is workable only under the conditions of lower slope gradients and rock fragment contents.

    更新日期:2018-06-22
  • Impacts of reservoir operations on multi-scale correlations between hydrological drought and meteorological drought
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-20
    Jiefeng Wu, Zhiyong Liu, Huaxia Yao, Xiaohong Chen, Xingwei Chen, Yanhui Zheng, Yanhu He

    Although numerous studies have investigated the relationships between hydrological drought (HD) and meteorological drought (MD) in different regions, few studies have examined the influence of reservoir operations during drought periods on such relationships, particularly at multiple time scales. This study presents a useful framework to examine the influences of reservoir operation rules during drought periods on the multi-scale correlations between HD and MD. Two standardized drought indices (Standardized Streamflow Index (SSI) and Standardized Precipitation Index (SPI)) with different timescales (1, 3, 6, 12, and 24 months) were used to compare the pre-reservoir and post-reservoir periods. Also, a simple algorithm was proposed to examine the difference value (Dvalue) between the inflow and outflow under different reservoir operation rules and it was used to evaluate the impacts of the reservoir operation rules during the drought on the correlation of the HD and MD. Monthly streamflow and precipitation records from 1960 to 2015 and monthly inflow and outflow records of a large reservoir (Xinfengjiang reservoir) during 1974–2009 in the basin of the Dongjiang River in south China were used to demonstrate the applicability of the analysis methodology. The results indicate that (1) the reservoir operations during the post-reservoir period (1974–2015) exerted a significant influence (positive impact) on the evolution of the short-term (1 and 3 months) HD by reducing the drought duration and alleviating its magnitude and altered the linear correlation between the HD and MD compared to the pre-reservoir period (1960–1972). However, the effects on the long-term (e.g., 12 and 24 months) HD and its correlation with the MD were not apparent. (2) The impacts of the reservoir operation under the drought condition on the relationship between the HD and MD were clearly different from those under normal rules. This study provides additional information for policy-makers to regarding reservoir management during a drought.

    更新日期:2018-06-22
  • Assessment of the impact of sea-level rise on steady-state seawater intrusion in a layered coastal aquifer
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-20
    Wenlong Shi, Chunhui Lu, Yu Ye, Jichun Wu, Ling Li, Jian Luo

    Previous studies on the impact of sea-level rise (SLR) on seawater intrusion (SWI) are mostly based on the assumption of a homogeneous coastal aquifer. In this study, we extend those studies by investigating SLR-induced SWI in a layered coastal aquifer using the analytical method developed by Strack and Ausk (2015). We provide analytical solutions for steady-state SWI in confined and unconfined coastal aquifers, where both constant-head and constant-flux inland boundary conditions are considered. The analysis based on a three-layer aquifer indicates that in general aquifer stratification affects either or both the initial location and response distance of the interface toe. Specifically, for flux-controlled unconfined coastal systems, the toe response distance driven by SLR is a linear function of the hydraulic conductivity of the top layer and independent of hydraulic conductivities of lower layers. Using an equivalent homogeneous hydraulic conductivity (derived based on the initial interface toe location before SLR) would result in overestimation or underestimation of the toe response distance, depending on the hydraulic conductivities and thicknesses of the layers. For flux-controlled confined layered coastal systems, by contrast, SLR can not cause variation of the steady-state interface toe location, which is consistent with previous findings for homogeneous coastal aquifers. The interface toe location in head-controlled layered coastal systems is only a function of relative hydraulic conductivities between the layers. Moreover, the effect of the layer thickness on the interface toe location and response distance in the head-controlled system exhibits a more complicated pattern than in the flux-controlled coastal system, as changing the layer thickness changes both the overall aquifer transmissivity and inland freshwater flux. The results obtained enhance the understanding of the impact of SLR on SWI, which could provide a first-order assessment tool for relevant practitioners.

    更新日期:2018-06-22
  • Temporal dynamics of soil moisture and rainfall erosivity in a tropical volcanic archipelago
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-20
    Abelardo Antônio de Assunção Montenegro, Thais Emanuelle Monteiro dos Santos Souza, Edivan Rodrigues de Souza, Suzana Maria Gico Lima Montenegro

    Soil water availability has a strong role on vegetation conservation and biodiversity, particularly at vulnerable environments such as archipelagos, subject to significant temporal changes of climate and rainfall, which influence soil weathering and erosion processes. Few field studies on hydrology of volcanic islands in the Atlantic Ocean have been developed focusing on soil and water temporal dynamics and conservation, mainly because such studies require data with high temporal resolution, and also due to the financial costs involved with field data acquisition at such remote places. Considering the importance of soil moisture content to several hydrological processes and islands environmental sustainability, this study aimed to investigate the soil water temporal dynamics in relation to different rainfall patterns and also the rainfall erosivity and its temporal variation, and the resulting infiltration depths, during a typical hydrological period, in an experimental plot at the main watershed of Fernando de Noronha, in the Brazilian Atlantic Coast. Rainfall was recorded every 5 minutes, and soil moisture was intensely monitored by 16 moisture probes, installed at 10-40 cm and 40-70 cm layers, during three years, representing the typical local hydrological regime and seasons. Rainfall bursts pattern were identified and described. Experimental data allowed a hydrological model to be calibrated and validated, providing estimates of infiltration depths, which can be valuable for water resources planning and management. Hydrological patterns were determined for each erosive rainfall, depending on the precipitation peak position, as advanced, intermediate and delayed. The soil water effectiveness was also evaluated and related to the different rainfall patterns. Soil moisture is highest from April to June, close to saturation; whilst for the other months the values were close to the residual value. The rainfall erosivity in the archipelago was identified as moderate to strong, and the most frequent rainfall pattern was the advanced. Fast wetting-drying cycles during the rainfall events were observed, due to rainfall intermittency, evapotranspiration, and to soil hydraulic conductivity. It was observed the prevalence of high moisture indexes, with percentages higher than 40% (extremely effective level) for both investigated depths within the first 70 cm of soil, essential for plant water uptake. The observed rainfall erosivity highlights the importance of defining local strategies for soil and water conservation aimed at water security in the island. Based on a simulation model, which was successfully calibrated (Nash-Sutcliffe Eficiency Index NS=0.76) and validated (NS=0.81) for periods in the wet season, high infiltration depths have been identified, which contributes to canopy conservation in the archipelago.

    更新日期:2018-06-22
  • Hydroclimatic Response of Evapotranspiration Partitioning to Prolonged Droughts in Semiarid Grassland
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-21
    Dongmei Han, Guoqiang Wang, Tingxi Liu, Bao-Lin Xue, George Kuczera, Xinyi Xu

    A warming climate is expected to perturb the hydrological cycle, resulting in changes to both the frequency and duration of drought, especially in arid and semiarid grassland. Although considerable attention has been paid to the responses of key water fluxes to severe drought, few have explored the effects of prolonged drought on evapotranspiration (ET), its partitioning into vegetation transpiration (T) and soil evaporation (E), and its relationship with vegetation productivity. In this study, we used a combination of the eddy covariance (EC) flux technique and satellite remote sensing products to evaluate the effects of prolonged drought on ET components based on the concept of underlying water use efficiency (uWUE). The results showed T accounted for about 51% (standard deviation ± 0.03%) of ET during prolonged drought lower than those in normal and/or wet years (range, 59- - 62%). We detected strong positive relationships between the T/ET ratios and aboveground biomass (AGB), leaf area index (LAI), and precipitation (R2 of 0.80, 0.58, and 0.49, respectively). The specific responses of ecosystem functioning to prolonged drought indicated that grassland ecosystem was able to resist the drought disturbance and retain vegetation growth to a certain extent unless extreme drought hit. The results implied that more intense and prolonged droughts will result in ecological degradation and substantial changes in ecosystem functioning. And these results improve our understanding of how the climate change will affect the function and structure of grassland ecosystem.

    更新日期:2018-06-22
  • From ENSEMBLES to CORDEX: evolving climate change projections for Upper Danube River flow
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-21
    Philipp Stanzel, Harald Kling

    Regional Climate Models (RCMs) generate past and future climate simulations that serve as input for subsequent modelling of impact projections. The most recent coordinated regional climate modelling initiative, CORDEX, provides RCM data for Europe with increased spatial resolution (12.5 km for the CORDEX EUR-11 ensemble) and based on the new Representative Concentration Pathways (RCPs). RCM data from the previous initiative ENSEMBLES had a spatial resolution of 25 km and was based on the SRES emission scenarios. In this contribution we explore the development from ENSEMBLES to CORDEX in a hydrological impact study for the Upper Danube, focussing on the representation of past climate and projections of the future for climate and resulting river discharge. We replicated a hydrological modelling framework, including RCM downscaling and bias correction, that used data of 21 ENSEMBLES RCMs under SRES A1B emission scenario (Kling et al. 2012), and now applied CORDEX EUR-11 data of 32 RCM simulations under RCP4.5 and RCP8.5 emission scenarios. Results with CORDEX show a small improvement in the representation of historical precipitation, but a decline in the accuracy of historical temperature simulations, despite the increase in spatial model resolution. The tendency of ENSEMBLES climate projections is reproduced with the CORDEX RCMs, albeit with slightly higher precipitation in the CORDEX data, yielding a less pronounced reduction in future mean annual discharge for the Upper Danube at Vienna. The previously identified change in discharge seasonality – increasing winter discharge and decreasing summer discharge – is confirmed with the new CORDEX data. Updating climate impact simulations in the presented rigorous replication framework allows analysing specific new information in the latest generation climate model data as well as crystallizing essential expectable patterns of change that need to be addressed in adaptation strategies.

    更新日期:2018-06-22
  • Spatio-temporal diel DOC cycles in a wet, low energy, northern catchment: highlighting and questioning the sub-daily rhythms of catchment functioning
    J. Hydrol. (IF 3.727) Pub Date : 2018-06-21
    C. Tunaley, D. Tetzlaff, H. Wang, C. Soulsby

    Sub-daily variations in the rates and dominance of the main controls of stream dissolved organic carbon (DOC) concentration (production, mobility and instream processes) have the potential to create a subtle sub-daily rhythm of DOC variation in streams. We used high-frequency data, covering the spring-summer-autumn period, which included discharge, specific conductivity, pH, groundwater levels, temperature, evapotranspiration and solar radiation to investigate the interplay between factors potentially driving diel DOC cycles in northern catchments. We focused on a peatland dominated 1st order stream (0.65 km2) before investigating the propagation of the signals downstream to a 2nd order stream (3.2 km2), with a lower percentage of peat fringing the stream channel. DOC cycles in the 1st order stream had a median peak time of 14:00 hrs and temporally varying amplitude, with a median of 0.61 mg l-1. Results supported the hypothesis that diel DOC cycles at the site are driven by hydrological processes, specifically the viscosity-effect theory: viscosity-driven increases in flow from the riparian area in the afternoon flush DOC from the peat to the stream. The temporal variability in the amplitude of the diel DOC cycle was controlled by antecedent temperature. Downstream, the diel DOC signal was weaker, with around 4-fold lower amplitudes and minima in the afternoon. The lower proportion of riparian peat downstream appeared to reduce the influence of terrestrial processes on DOC cycles. In-stream photodegradation and decomposition likely became more dominant as connectivity between DOC sources and stream reduced. The study highlighted that even in climates such as the Scottish Highlands, where energy input is relatively low and precipitation frequent, sub-daily hydrological and biogeochemical rhythms occur. Unravelling the intricacy of such diel cycles is fundamental to fully understanding stream functioning and the global carbon cycle.

    更新日期:2018-06-22
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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