How Significantly do Land Use and Land Cover (LULC) Changes Influence the Water Balance of a River Basin? A Study in Ganga River Basin, India

Changes in LULC, primarily conversion of natural vegetation to built-up and agricultural areas, has been one of the key modes of human modification of the global environment. Assessment of the consequences of these changes for hydrological processes is vital for sustainable management of water resources. In this study, the impacts of land use and land cover (LULC) changes on the evapotranspiration (ET) and runoff in the Ganga river basin, India during the period of 1975–2010 are assessed. Variable infiltration capacity (VIC), a physically distributed macro-scale hydrological model, is used with a grid cell resolution of 0.125° with a daily time step to simulate hydrological fluxes. The moderate resolution imaging spectroradiometer (MODIS) LAI product MCD15A3 is used to extract monthly LULC class-wise leaf area index values to parameterize the VIC model. The results indicate that the VIC model is a powerful model for assessing the hydrologic impacts of LULC change. The Nash–Sutcliffe efficiencies for the monthly stream flow were 0.650 and 0.565 during calibration and 0.764 during validation, respectively. Single-cell model simulations show that expansion of the built-up area at the cost of vegetation is the change that affected the water balance of the study area most significantly. The effects of LULC changes are greatest during the monsoon. However, during the dry season, there are similar ET and runoff responses from most of the LULC classes because of the low soil moisture. The overall changes in the ET and runoff due to LULC changes in the study area are found to be too small at the basin. We observe that at the basin scale, the negative impacts on the ET and runoff are compensated by the positive impacts.