The Variations And Response Of Water And Sediment Exchange Between Yangtze River And Dongting Lake After The Three Gorges Reservior Impondment

After the impondment of Three Gorges Reservior, the runoff hydraulic characteristics and sediment generation of the middle and lower reaches of the Yangtze River changes. The changes have impacted on the diversion from the Yangtze River to Dongting Lake, the runoff and sediment of Chenglingji, and the runoff and sediment exchange between the river and the lake. The dissertation shows the summing up of the exchange changes between the Yangtze River and Dongting Lake, and analysis the response of runoff and sediment exchange to the runoff hydraulic characteristics and sediment generation of the Three Gorges outbound station. The results show:1. Get the inter-annual and intra-annual variations of runoff and sediment diversion at three outlets in Yangtze River, and the response relationship between the water level, discharge, sediment discharge, runoff and sediment diversion ratios of the three outlets and the runoff hydraulic characteristics and sediment generation of the Three Gorges outbound station. On one hand, after the impondment of Three Gorges Reservior, the annual average discharge, sediment discharge, runoff and sediment diversion ratios of three outlets all decreased. And the runoff diversion ratio has a decreasing tendency. On the other hand, the impoundment of the Three Gorges reservoir can be divided into three periods:water supply period, flood control period and storage period. In water supply period, the three outlets discharge and runoff diversion ratio increased; in flood control period and storage period, the three outlets discharge, sediment discharge, runoff and sediment diversion ratios all decreased; the water level of Xinjiangkou Station went up in water supply period, while the others all reduced. The response equations between the three outlets runoff and sediment discharge and the runoff hydraulic characteristics and sediment generation of the Three Gorges outbound station are respectively.2. Get the runoff and sediment changes at Chenglingji Station, propose the quantized coefficients of Chenglingji water and sediment’s supplement function on the Yangtze River, get the inter-annual and intra-annual variations of water and sediment at Chenglingji, and get the response relationship between the water level, discharge, sediment discharge at Chenglingji Station and the runoff hydraulic characteristics and sediment generation of the Three Gorges outbound station. For one thing, after the impondment of Three Gorges Reservior, the average discharge and sediment discharge decreased and have a decreasing tendency. For another thing, the water supplement coefficient decreased in the all three period, while the sediment supplement coefficient increased. At last, the response equations between the runoff and sediment discharge at Chenglingji Station and the runoff hydraulic characteristics and sediment generation of the Three Gorges outbound station are respectively.3. Propose the quantized indexes of the water and sediment exchange between Yangtze River and Dongting Lake, analysis the changes of them, and get the response relationship between the indexes and the runoff hydraulic characteristics and sediment generation of the Three Gorges outbound station. After the impondment of Three Gorges Reservior, the water exchange index stayed the same in water supply period, but decreased in flood control period and storage period; the sediment exchange index decreased in water supply period and storage period, but increased in flood control period. Over all the three period, the water exchange enhanced and the sediment exchange weakened. The response equations between water and sediment exchange indexes and the runoff hydraulic characteristics and sediment generation of the Three Gorges outbound station are and respectively. And it is beneficial to the relationship between the Yangtze River and Dongting Lake when.