Abstract:

Through the analysis of hydrological data measured form 1951 to 1991,it is shown that water and sand entering the Dongting Lake form main rivers rivers along the southern bank of the Jingjiang count 300.2×10⁹m³ and 191.84×10⁶t per year on average,respectively.The lardest monthly amounts of water and sand entering the lake occur from April to July.The ratio of the runoffs in high and low water years is 1.88~2.78,while that of the sediment comes to 2.96~13.5.After cutting off a crook of the Jinsjiang,the amounts of water and sand entering the lake from the four entrances shows a high-Water and low-water periodic cycle,and the period is about ten years,in agreement with that data of Datong Station in the Yangtze River.Floed water occurs more possibly from July to August.Any combination of flood-peak encounter Can Cause severe flood disaster in the Dongting Lake area.In flood season,the amount of water and sand entering the lake ig so large that 155.1×10⁶t of sediment accumulate on the lake bed each year,shrinking the area of water surface,and capacity and depth of the lake.

Key words: The Jingjiang River, The Dongting Lake, Runoff amount Sediment discharge