The impacts of climate change and land cover/use transition on the hydrology in the upper Yellow River Basin, China

Observed streamflow over the past decades in the upper Yellow River Basin (UYRB) was examined for changes in hydrological regime. The modified Variable Infiltration Capacity (VIC) model was employed to better understand climate change impact and long-term and recent land cover/use change impact as it relates to the "Grain for Green Project" and "Three Rivers Source Region Reserve" on water resources by examining mechanisms behind observed streamflow changes. UYRB hydrological regimes have undergone changes over the past decades as reflected by a decrease in wet and warm season streamflow, and annual streamflow. Progressively more streamflow has been generated in the early part of the year compared to the latter part, consequently leading to the earlier occurrence of the day representing the midpoint of yearly mass flow. VIC simulations suggest that these changes in observed streamflow were due to the combined effects of changes in precipitation, evapotranspiration, rainfall runoff, and baseflow and were caused primarily by climate change above Tang Nai Hai (TNH) hydrometric station. Below TNH where human activity is relative intense, land cover/use change and reservoir release impacts became important. Changes in snowmelt runoff were negligible over the past decades. Owing to this, snowmelt runoff appeared to play only a modest role in the changing hydrology of the region. The conservation programs were shown to start to exhibit some positive impacts on water resources in the UYRB.