273 / 2024-02-28 21:53:35

Hydrological impacts of cascading reservoirs in the middle and lower Hanjiang River under changing climate and land use

Cascade reservoirs,Hydrological impacts,SWAT,IHA,Lower-middle Hanjiang River basin

Anthropogenic activities such as the construction of cascade reservoirs have deeply disturbed the natural streamflow conditions and exerted threats to riverine ecosystems worldwide under a changing climate. It is crucial to understand the hydrological impacts of cascading reservoirs and evaluate the contributions of various factors from the aspects of human activities and climate change. A comparison modeling method is adopted by integrating the Soil and Water Assessment Tool (SWAT) and Indicators of Hydrological Alteration (IHA) method in the Hanjiang River basin in central China, to reveal the hydrological impacts of the cascade reservoirs, changing climate, and land use variability. Scenarios including baseline, climate variability, and land use variability are modeled and further compared with the actual condition that represents the scenario in which all factors present influences to streamflow regime so that the contributions of each factor are studied separately. The results showed that the construction and operation of cascading reservoirs play the most important role in regulating the streamflow regime which caused an obvious increase in streamflow in winter and spring, and weakened the flood in summer and fall with a raised annual baseflow. The small flood events are regulated by increasing the event numbers and decreasing the lasting time. Climate variability has caused the second-largest influence which caused the flow to increase in winter and summer and flow decrease in the rest of the months. Land use change causes low alterations in the streamflow regime. The ecological influences of the altered hydrological conditions are further discussed by calculating the Environment Flow Components (EFCs) parameters based on the IHA.