Contribution of Climate Change and Landuse / Landcover Change on Variations of Hydrological Processes in The Water Towers of Yangtze River, China

The impact assessment of landuse / landcover change (LULCC) and climate change (CC) on the runoff in a highly elevated watershed has key importance in terms of sustainable water resources and ecological developments. In this research, statistical technique was deployed with the addition of Soil and Water Assessment Tool (SWAT) in the Water Towers of Yangtze River (WTYZ). The coefficient of determination (R²) and Nash-Sutcliffe Efficiency (NSE) were used as a decision criterion to ensure the performance of model simulations. The model performed satisfactory with monthly R² = 0.80 to 0.83 and NSE = 0.63 to 0.69 during calibration (1985 - 2000) and (2001 – 2016) periods. Major LULCC transformations were assessed from low grassland to medium grassland (2.017%) and wetlands (0.90%), bare land to medium grassland (0.23%) and glaciers to wetland (16.83%), high grassland to medium grassland (5.77%) during 1990s and 2005s. Impact of CC increased runoff by 97.97% and decreased evapotranspiration by -5.15% of total runoff and evapotranspiration respectively. It was also noteworthy that LULCC caused the increase in runoff and evapotranspiration by 2.02% and 105.15% relative to totals, respectively. Thus, the variations of runoff in the WTYZ are mainly impacted by landuse/landcover, while climate change have relatively least impacts.