在实测的 1 974,1 988,1 998年 1∶ 2 .5万地形图的基础上,利用地理信息系统的数据处理和空间分析方法,分析洞庭湖 2 4年来的冲淤规律,得到了 2个时期 (1 974～ 1 988,1 988～1 998)洞庭湖冲淤量和冲淤区域的空间分布位置。研究表明,洞庭湖近 2 4年来总的趋势是淤积的,局部有冲刷,但总体上淤积量大于冲刷量,湖盆平均淤高 0 .43m。 2个时期年均冲淤厚度没有明显的变化,为 0 .0 1 7m/ a。以两期冲淤变化的趋势预测了 2 0 1 0年三峡工程全部完工时洞庭湖的冲淤变化状况,结果表明,1 998～ 2 0 1 0年间洞庭湖将平均淤高 0 .33m。

The sediments of the Dongting Lake come from four channels (one of them was closed in 1959), connected with the Yangtze River, four tributaries (Lishui, Yuanjiang, Zishui and Xiangjiang) and local area, and some of them are transported into the Yangtze River at Chenglingji, which is located at the exit of the Dongting Lake, some of them deposit into drainage system in the lake region and the rest deposit into the lake The annual mean sediment is 166 555×10 4 t, of which 80% come from the four channels, 18% from the four tributaries and 2% from local area, whereas 26% of the total sediments are transported into the Yangtze River and 74% deposited into the lake and the lake drainage system The sediment budget in the lake can be expressed as follows: V FourMouth +V FourRiver +V Location +V Erosion -V Out =V LakeSediment +V DrainagesystemSediment where V FourMouth is the sediments from the channels which connect the Yangtze River, V FourRiver is the sediments from the tributaries, V Location is the sediments from local area, V Erosion is erosion from the lake, V Out is the sediments carried into the Yangtze River,V LakeSediment is the sediments deposited in the lake, and V DrainageSystemDediment is the sediments deposited in the lake drainage basin Based on topographic maps in 1974, 1988 and 1998, and the spatial analysis method with geographic information system (GIS), the changes in sediment deposition and erosion are studied in this paper By overlay analysis of 1974 and 1988, 1988 and 1998, erosion and sediments deposition areas are defined The main conclusions are: (1) sediment rate in the lake is larger than erosion rate from 1974 to 1998 The mean deposition in the lake is 0 43 m; (2) annual sediment deposition is the same between 1974～1988 and 1988～1998, but the annual volume of deposition and erosion of 1988～1998 is bigger than that in 1974～1988; (3) before the completion of the Three Gorges Reservoir, there will be 7 82×10 8 m 3 sediment deposited in the lake, which would make the lake silted up by 0 33 m; (4) in the lake, the deposition area is found in the north of the east Dongting Lake, the south west of the south Dongting Lake, and the east of the west Dongting Lake; while the erosion area is in the south of the east Dongting Lake, the middle of the south Dongting Lake, the west of the west Dongting Lake.