A holistic approach to projecting streamflow and analyzing changes in ecologically relevant hydrological indicators under climate and land use/ cover change

Understanding streamflow change and its ecological impacts under climate change and land use/cover change (LUCC) makes possible the improvement of water and ecological governance decision -making. Gaining a comprehensive understanding of the drivers of historical streamflow changes can provide valuable insights for effective projections of future streamflow. Meanwhile, future changes in ecologically relevant hydrological indicators need more attention to maintain the ecological stability of rivers. This study has developed a holistic framework based on a physically based model (the Variable Infiltration Capacity model, or VIC) and the indicators of hydrological alteration (IHA) method to decouple the drivers of historical streamflow change and to project changes in future streamflow and ecologically relevant hydrologic indicators. The proposed framework was applied in the upper Han River basin (UHRB), which is the water source for the water diversion project in China. The results showed that climate change contributed 99.67 % of the streamflow decrease in the 1980-1990s and 108.21 % and 102.09 % of the streamflow increase in the 1990-2000s and 2000-2010s respectively. LUCC had a weak impact on streamflow in these three periods. Projected climate change will further exacerbate streamflow change. The projected monthly streamflow is expected to increase from October to December. The counts of streamflow pulses are expected to decrease, but the duration of each high pulse will increase. These changes will cause stress in floodplain vegetation, alterations to stream chemistry, reductions in fish diversity (decreased streamflow pulses), and alterations to river landscape and animal habitat (increased flood duration). The developed framework is expected to provide significant technical guidance for water resource management and river conservation.