Modified Hydrological Regime on Irrigation and Water Supply in Lake Areas: A Case Study of the Yangtze River–Dongting Lake

Abstract

Lake systems are of fundamental significance for the ecological environment and social development. Driven by climatic changes and human activities, the hydrological situation of rivers and lakes has been altered considerably, and it has directly affected the reliability of irrigation and water supply in lake areas. In the case of the Yangtze River–Dongting Lake area, the quasi-equilibrium of their hydrological states and water balance have been affected by the operation of the Three Gorges Project that has led to irrigation and water supply problems across the lake area. Ever since, the available water supply in the Dongting Lake area has decreased by 31.5% and 47.7% during the months of September and October, and the overall water level in the lake area has dropped by 0.8–2.0 m. The proportion of domestic and agricultural irrigation water demands to available water supply in the Dongting Lake area is very small, and the decline of water level is the main reason for the lack of water supply in Dongting Lake area, Although the total amount of water in the lake area is still above the water supply threshold, an obvious decreasing trend has been observed in the fulfillment of the demand for both irrigation and water supply in urban and rural regions. Additionally, the fulfillment of secured water supply and irrigation requirements has respectively dropped from 95% to 78% before the operation of the Three Gorges Project to 82% and 46% after it. Meanwhile, the total water shortage increased from 57.683 to 143.607 million cubic meters. By advancing or postponing impoundment schedules, the impact of the Three Gorges Reservoir on irrigation and water supply in the lake area during September and October can be alleviated, and the water supply capacity can be respectively increased by approximately 1.3% and 1.4%. The highlights of this study include the quantification of the impacts of the operation of large-scale water conservancy projects at the level at which the requirements on irrigation and water supply in the lake area are satisfied, and the prediction of the trends for future evolvement. In addition, corresponding strategies that provide a technical reference for the comprehensive regulation and control over water resources and the security of water supply in the river basin are discussed.

Changes in Lake Inundation and Shrinkage Within the Framework of Coevolutionary River-Lake state

“…Additionally, suitable water supplementation plans should be implemented to increase the ow from the Li and Yuan Rivers when the in uence of the Yangtze River weakens. This can help to alleviate the severe degradation trend in the western DTL region (Fang et al, 2022). Furthermore, efforts should be made to reconstruct the natural hydrological rhythm and maintain the natural connectivity in the region.…”

Spatial and Temporal Evolution Characteristics of Low Water Level Based on 70 years’ Measured Data: A Case Study of Dongting Lake in China

“…Due to the low water level drop, the wetland vegetation pattern had significantly changed after the operation of TGD, mainly as a result of changes in submergence condition (Hu et al, 2018). The decline in water level has caused the lack of water supply in the Dongting Lake area (Fang et al, 2022). In addition, some studies believe that the TGD has provided some benefits for migratory birds by changing the spatial and temporal distribution of low water level (Zhu et al, 2021).…”