Dynamic Study on the Water Ecological Environment of Dongting Lake in the Context of the Operation of the Three Gorges Project in the Last 25 Years
Since the operation of the Three Gorges Project in 2003,the impact on the water environment in the middle and lower reaches of the Yangtze River has attracted more attention.Based on the monitoring results of 11 sites in Dongting Lake over the past 25 years,this study analyzed the spatial and temporal characteristics of water conditions and water environment quality in Dongting Lake in the context of the operation of the Three Gorges Project,and clarified the main controlling factors for the evolu-tion of the water environment in Dongting Lake.The results showed that from 1996 to 2015,the average annual water volume and sediment transport volume of the three Changjiang estuaries were(1.83～10.46)×1010 m3 and(1.07～147)×106 t,respectively.After the operation of the Three Gorges Project,the lake water intake and sediment transport volume decreased significantly by 27%and 87%,respectively.The main water quality indicators of total nitrogen(TN)increased significantly from 1999 to 2022,while the con-centration of tatal phosphorus(TP)decreased significantly,and the whole lake was the mesotrophic level,while East Dongdongting Lake was the mild eutrophication level.The phytoplankton density was(9.00～272.03)×104 ind./L,and increased year by year.The dominant groups of phytoplankton gradually changed from diatoms and cryptophytes to chlorophyta and cyanobacteria.Overall,hy-drological regulation is the key element to maintain the nutrient balance and water environment safety of Dongting Lake.In addi-tion,strengthening the control of agricultural surface pollution,promoting comprehensive clean production,and effectively intercept-ing pollutants from the lake inlet and upstream rivers through habitat improvement and ecological restoration are the main measures of the management of the Dongting Lake Economic Belt to carry out the comprehensive management of Dongting Lake and water quality improvement.
NETL
NSTL
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