Effects of land use changes on the ecological operation of the Panjiakou-Daheiting Reservoir system, China.

The problem of insufficient water for ecological purposes in the Luanhe River basin requires urgent resolution. The regional hydrological cycle is affected by the Panjiakou-Daheiting Reservoir system and by changes in land use in the upper watershed. Therefore, this system was selected as a study area to simulate ecological reservoir operation and analyze the effects of changes in land use on ecological operation. A physical habitat simulation model (PHABSIM) was built to determine the minimum and suitable ecological water demand. Then, an ecological reservoir operation model using an improved differential evolution (DE) algorithm was established. Simulated inflow data under the land use conditions in 1970 and 2015 were input into the model, and the effects of changes in land use on ecological operation and on the weighted usable area (WUA) for cyprinoids were calculated. The results show that ecological reservoir operation significantly improves the ecological water supply and increases cyprinoid habitat. The changes in land use led to a decrease in annual runoff, which further reduced the urban water supply by 0.67%–2.25% and the ecological water supply by 0.45%–2.04% at different flow frequencies. The land use changes also caused the WUA to decrease by 1746–2999 m2/km at different flow frequencies, with a decrease rate of 1.04%–6.28%. This study could provide valuable information for water resource managers operating reservoirs in river ecosystems and planning to cope with water shortages caused by land use change in water-deficient areas. • Determining the ecological water demand by synthesize hydrological and habitat methods. • The changes in land use result in a decrease in water supply and fish habitat. • Urban water supply is most affected by changes in land use at different flow frequencies. • Effects on the ecological water supply become stronger as the flow frequency increases. [ABSTRACT FROM AUTHOR]