Abstract
Hydrological regime changes in the river–lake system and their influences on the ecological environment downstream dams have attracted increasingly more attention all over the world. The Dongting lake downstream of the Three Gorges Dam (TGD) in the Yangtze River has been experiencing a series of hydraulic and hydrological changes over the last decade. The hydrological and ecological influences of the TGD flow regulation on the Dongting river–lake system and its functional mechanism during the impounding periods remain extremely unclear. This study examines the hydrological changes in the Dongting river–lake system based on a 1D/2D coupled hydrodynamic model. In particular, the inflow boundary of the model with and without the TGD was applied with the outflow and inflow of the TGD, respectively, during the same regulation periods. The results show that the diverted flow from the Yangtze River into the Dongting lake and outflow from the lake back to the river drastically decreased during the impounding periods, especially in October. The decreased water exchange between the Yangtze River and the Dongting lake impaired the water residence capacity to some extent in the lake. Stage decrease in the lake area resulted in a significant reduction in the water volume of the Dongting lake with the same time percentage. In addition, the obvious drainage effect in Dongting lake due to the increased stage difference and current speed after the TGD operation was the essential cause of hydrological changes in the lake area. These results provide an improvement in the understanding of impoundment influences on the large river–lake system and give some practical information for ecological environment management in similar river–lake systems.
Highlights
Lakes, as one kind of the most important water providers, widely exist on the earth
Hayashi et al simulated the daily runoff processes based on an integrated catchment model in the Yangtze River basin and examined the hydraulic effect of the mainstream on the outflow of the Dongting lake; the results showed a good agreement of hydrologic budget between the observed and simulated ones [26,27]
The research objectives of this paper are to (1) examine the changes in the water exchange with and without the Three Gorges Dam (TGD) and to evaluate the variation in water retention capacity of the Dongting lake based on a 1D/2D coupled hydrodynamic model; (2) analyze the variations in the lake level and water volume during the impounding periods after the operation of the TGD; and (3) further explore the formation mechanism and its dominant factors of the hydraulic and hydrological changes in the river–lake system, which will be significantly conductive to relieve the adverse influences on the river–lake system
Summary
As one kind of the most important water providers, widely exist on the earth. Most of these lakes connect with some rivers, so the river–lake system is the common form in natural basins [1,2].A fifth of the world’s surface freshwater was held in the five Great Lakes and their connecting rivers in North America [3]. As one kind of the most important water providers, widely exist on the earth. Most of these lakes connect with some rivers, so the river–lake system is the common form in natural basins [1,2]. A fifth of the world’s surface freshwater was held in the five Great Lakes and their connecting rivers in North America [3]. Other lakes such as Saimaa Lake in Finland, Peace-Athabasca Delta system in. Lakes in a river–lake system provide the necessary elements for plant growth and the important habitats for wildlife [7]
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