Since the 1980s, the state of Mato Grosso, Brazil, exhibits high rates of Cerrado conversion in favour of soybean expansion and cattle ranching. This conversion process becomes obvious in the upper Rio das Mortes macro-catchment. The objective of this study was to assess the influence of future land use changes on the discharge dynamics of the Rio das Mortes River. A single catchment approach was applied with the physically-based water balance simulation model WaSiM 8.5.0 (Schulla and jaSper 2007) to simulate land use scenarios. In Scenario 1, only small pasture sites (< 1 km²) were converted into the respective land use type surrounding them (i.e. cropland or Cerrado vegetation), whereas in Scenario 2 all pasture sites were converted into cropland and all Cerrado patches were then transformed into pastures. The WaSiM model was calibrated and validated based on discharge data measured at two gauging stations, achieving Nash-Sutcliffe coeffcients of 0.81 calibration) and 0.68 (validation). Main problems in modelling arise because of scarce spatial distributed data on subsurface parameter and vegetation parameter (Cerrado biome). Therefore, the use of the numerical groundwater model and manifold calibration runs were essential in this modelling approach to allow the simulation of the high levels of baseflow during the dry season and the transition from the dry to the wet season. The immediate rise of the baseflow in response to the increasing precipitation at beginning of the rainy season is a result of high soil hydraulic conductivity and groundwater recharge. These soil characteristics apparently persist on newly-created pasture and cropland sites, which still exhibit high ksat values after deforestation. Simulated evapotranspiration is comparable to literature values (Eddy flux measurements, MODIS-EVI calculation) and recently done paired micro-catchment studies in this catchment. The scenario analysis indicates that there are only small differences in runoff volume, which is directly related to the precipitation changes. In the scenario 2, groundwater recharge and base flow increase, whereas surface runoff does not. Therefore, the ongoing land use intensification with pasture conversion to cropland, remaining high infiltration and slight increase of evapotranspiration may not change runoff volume and discharge characteristics.

中文翻译：

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土地利用变化对塞拉多生物群落（巴西里约达斯莫特斯）水平衡影响的基于过程的建模

自 1980 年代以来，巴西马托格罗索州的 Cerrado 转化率很高，有利于大豆扩张和养牛。这种转化过程在 Rio das Mortes 大流域上游变得明显。本研究的目的是评估未来土地利用变化对 Rio das Mortes 河流量动态的影响。单一集水区方法与基于物理的水平衡模拟模型 WaSiM 8.5.0（Schulla 和 jaSper 2007）一起应用于模拟土地使用场景。在情景 1 中，只有小型牧场（< 1 平方公里）被转换为它们周围各自的土地利用类型（即农田或塞拉多植被），而在情景 2 中，所有牧场都被转换为农田，然后所有塞拉多斑块都被转换为牧场。WaSiM 模型根据在两个计量站测量的排放数据进行校准和验证，实现了 0.81 校准）和 0.68（验证）的 Nash-Sutcliffe 系数。由于地下参数和植被参数（塞拉多生物群落）的空间分布数据稀少，建模中的主要问题出现了。因此，在这种建模方法中，使用数值地下水模型和流形校准运行是必不可少的，以便模拟旱季和旱季向雨季过渡期间的高水平基流。由于雨季开始时降水增加，基流立即上升，这是土壤导水率高和地下水补给的结果。这些土壤特征显然在新建的牧场和农田上持续存在，森林砍伐后仍表现出较高的 ksat 值。模拟蒸散量与文献值（涡流测量、MODIS-EVI 计算）相当，最近在该流域进行了配对微流域研究。情景分析表明，径流量差异很小，与降水变化直接相关。在情景 2 中，地下水补给和基流增加，而地表径流没有。因此，持续的土地利用集约化、牧草转耕、高渗透率和蒸散量略有增加可能不会改变径流量和流量特征。MODIS-EVI 计算）并最近在该流域进行了配对微流域研究。情景分析表明，径流量差异很小，与降水变化直接相关。在情景 2 中，地下水补给和基流增加，而地表径流没有。因此，持续的土地利用集约化、牧草转耕、高渗透率和蒸散量略有增加可能不会改变径流量和流量特征。MODIS-EVI 计算）并最近在该流域进行了配对微流域研究。情景分析表明，径流量差异很小，与降水变化直接相关。在情景 2 中，地下水补给和基流增加，而地表径流没有。因此，持续的土地利用集约化、牧草转耕、高渗透率和蒸散量略有增加可能不会改变径流量和流量特征。