Adaptive regulation based on the spatio‐temporal distribution of ecological flow surplus and deficit in the Hanjiang River basin

Ecological flow has attracted considerable attention because intensive dam construction can cause changes in the hydrological situation and subsequent ecological environment problems. In the Hanjiang River basin, 15 cascade reservoirs are due to become operational in the main stream in the coming years. In this study, the calculation method of ecological flow surplus and deficit was proposed, and the key periods (KPs) and key areas (KAs) of ecological flow deficits were identified. Adaptive regulation strategies were proposed based on a new method. Results show that (1) the wet and normal years are in a state of ecological surplus. In the dry year, there is an ecological flow deficit of 370 million m(3). The off-stream ecological water shortage is at its most serious in June. In the river channel, the ecological flow deficit usually appears in the winter. The Xiantao section in the lower reaches has a deficit every month in the typical water years. (2) In the off-stream region, the KPs cover months 6 to 9, and the KAs are the southeastern Hanzhong plain, Shiyan City, southeastern Nanyang basin, and the midwest of Xiangyang City. In the river channel, the KPs cover months 12 to 2 above the Shayang section, while in the downstream Xiantao section KA, the KP covers the whole year. The cooperative analysis of KPs and KAs can effectively improve the pertinence of watershed ecological flow regulation. Priority for water resources regulation in water deficient areas should be given to key areas in the key periods.