Original Research
Impacts of land use and land cover changes on hydrological processes and sediment yield determined using the SWAT model

https://doi.org/10.1016/j.ijsrc.2021.04.002Get rights and content

Highlights

  • Changes in land use impact sediment yield in the Amazon.

  • The SWAT model was calibrated and validated for an Amazon subbasin.

  • Soil types, land use, and slope are the main factors affecting sediment yield.

  • Subbasins dominated by pasture showed a positive trend and a break point.

  • Over 57% of forest areas have been converted to pasture on the IRW.

Abstract

Land use and land cover (LULC) changes strongly affect local hydrology and sediment yields. The current study focused on a basin in the Brazilian Amazon and had the following three objectives: (1) to perform an effective diagnosis of flow and sediment yield, (2) to evaluate the impacts of LULC changes over the last 40 years on the hydro-sedimentological variables, and (3) to investigate the impacts of the possible trends or breaking points in the flow, surface runoff, and sediment yield series. The Soil and Water Assessment Tool (SWAT) model validation showed that the simulated results were consistent with the data measured in the dynamic reproduction of flow seasonality. Furthermore, changes in LULC altered surface runoff, sediment yield, and flow according to the Mann-Kendall and Pettitt non-parametric tests. It was also observed that the sub-basins in which pastureland is predominant are more susceptible to increased surface runoff and sediment yield. According to trend and homogeneity tests, these sub-basins had break points in the time series of these variables. On the other hand, in the sub-basins whose land cover is predominantly forest, the time series is homogeneous and trendless. The current study highlighted the impacts that 40 years of LULC changes in an Amazonian basin had on hydro-sedimentological variables, which, in turn, can play an important role in changing the hydrological cycle, consequently these changes can also impact diverse human activities in the region, such as agribusiness, livestock, energy production, food security, and public water supply. Thus, it is concluded that the SWAT model is a good estimator of hydro-sedimentological processes in Amazonian basins and can be used by decision makers in the management of water and environmental resources.

Introduction

Current global trends such as population and economic growth, which often lead to increased food demands, exert great pressure on environmental resources worldwide (Aghsaei et al., 2020, Grey et al., 2014). These trends trigger changes in land use and land cover (LULC) with major impacts on hydrological processes (Aghsaei et al., 2020; Anand et al., 2018; Chow et al., 1988; Coe et al., 2009; de Oliveira Serrão et al., 2020; Guo et al., 2008; Scanlon et al., 2007). In addition to changes in the hydrological cycle, research attests to changes in the consumptive uses of water (energy production, food security, public water supply and industrial purposes). Studies have also demonstrated the environmental effects on the total suspended sediment and nutrient concentrations (Hwang et al., 2016), groundwater recharge and base flow (Budiyanto et al., 2015), flood frequency and interval (Alexakis et al., 2014), peak runoff (Ahn et al., 2014; Serrão et al., 2019; Silva et al., 2018a), and evapotranspiration (Silva et al., 2018b; Souza-Filho et al., 2016). According to Aghsaei et al. (2020), the main factors that contribute to LULC changes are rapid socioeconomic development, national resource conservation policies, and climate variability.

Brazil's largest biome, the Amazon, has been at the center of discussions when it comes to the ill-conceived transformation of forests into illegal grazing areas (Nature Editorial, 2018a). Recent changes in Brazil's environmental policies, namely the reduction of environmental licensing requirements and the deregulation of indigenous lands, have resulted in increased deforestation, wildfires, and even damage to the existing protected areas (Andrade, 2019; de Oliveira Serrão et al., 2020; Escobar, 2019; Nature Editorial, 2018a, Nature Editorial, 2018b; Rajão et al., 2020; Tollefson, 2019). The Amazon basin represents a large area of tropical forest and exerts a significant influence on local and global climate due to its role in the energy and water fluxes in the atmosphere-biosphere system (Stickler et al., 2013). Increasing deforestation rates in the Amazon put the water balance and environmental systems at a significant risk (Coe et al., 2009; de Oliveira Serrão et al., 2020; Lamparter et al., 2018; Nepstad et al., 2014; Serrão et al., 2019).

The conversion of forests into pasture lands in the Amazon began in the early 1970s with the construction of the Trans-Amazon Highway (Fearnside, 2005). Several settlements were established and later became the great cities known today as Marabá, Parauapebas, and Canaã dos Carajás among others. In order, to understand the dynamic processes of LULC changes, a detailed spatial and temporal scale analysis is necessary. In this context, hydrological models are powerful instruments for the monitoring and prognosis of LULC changes and have greatly evolved over the years (Arnold et al., 1998; Beven & Kirkby, 1979; Crawford & Linsley, 1966; Migliaccio & Srivastava, 2007; Pandey et al., 2016). For example, the Soil and Water Assessment Tool (SWAT) model has been used in various river basin-scale studies to simulate the quality and quantity of surface and ground water and also to predict the environmental impacts of land use, land management practices, and climate on the hydrological cycle (Abbaspour et al., 2015; Arnold et al., 1998; Bressiani et al., 2015; de Oliveira Serrão et al., 2020, de Oliveira Serrão et al., 2021; Gassman et al., 2014; Pereira et al., 2016; Silva et al., 2018a; Wang et al., 2019)

The Itacaúnas River Watershed (IRW) is one of the most affected by deforestation and mining watersheds in the Amazon. This large basin (42,000 km2) located in the eastern Amazon had 50% of its area deforested between 1970 and 2013 (Souza-Filho et al., 2016). Intense mining activities of great economic, environmental, and social relevance are carried out in this region. Therefore, the objectives of the current study follow three lines: (1) to perform an effective diagnosis of flow and sediment yield, (2) to evaluate the impacts of LULC changes over the last 40 years on the hydro-sedimentological variables, and (3) to investigate the impacts of the possible trends or break points in the flow, surface runoff, and sediment yield series.

Section snippets

Study area

The Itacaúnas River is a tributary of the Tocantins River. The IRW drains an area of 42,000 km2 and is located in the eastern part of the Brazilian Amazon in the southeast of the state of Pará (Fig. 1). Eleven cities with approximately 700,000 inhabitants are found within the area of the IRW, and the gross domestic product (GDP) of the area was worth approximately $ 7 billion in 2019 (Pontes et al., 2019). Amazon rainforest originally covered the area, but 57% of this coverage has been

Sensitivity analysis, flow calibration, and validation

Eleven parameters were chosen for the calibration process in the sensitivity analysis. According to Abbaspour et al., 2015, Abbaspour et al., 2018 and Arnold et al. (2012), the success of the calibration depends on two main factors: the physical factors of the input data (soil types, climate, and land use) and the dependence on the sensitivity analysis and calibration of the model.

Bruijnzeel (2004), Giertz et al. (2005), and Igwe (2011) pointed out that the types of soils in basins located in

Conclusions

This study evaluated the impacts of historical land use changes on hydrological processes using the SWAT model. The calibration of the model made it possible to note that some parameters are more influenced by water processes than others, providing the opportunity to improve the simulation of the basin. After the validation, the hydrological simulation efficiently represented the variability of the flows studied.

The temporal evolution of land-use changes resulted in great impacts on the basin's

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This study was conducted as part of the doctoral thesis of the first author, who would like to thank the National Council for Scientific and Technological Development (CNPQ) and the Academic Unit of Atmospheric Sciences (UACA) of the Federal University of Campina Grande (UFCG) in Brazil, for the financial aid (process number, 140740/2018-0) and support during this research study. We are very grateful to the anonymous reviewers and editors for their comments and considerations, which helped to

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