【摘要】 洞庭湖是长江中游典型的吞吐型过水湖泊,在调洪、蓄洪方面起重要作用。近百年来由于江水携带大量泥沙入湖及人工围湖垦殖,已使天然湖泊面积从5000km~2缩小为2740km~2。本文根据多时相陆地卫星象片所提供的信息,结合地面监测资料和历史图件,重点论述了洞庭湖的成因、近期变迁过程及淤积趋势。作者通过对入湖三角洲淤涨模式及湖流的分析,确定了洞庭湖的淤积部位和淤积量。文中强调了围湖垦殖对洪水调蓄的影响,并从宏观角度提出了洞庭湖治理意见。更多还原

【Abstract】 The Dongting Lake is a typical passing reservoir which adjusts both the inflow from and outflow to the mid-reach of the Changjiang (Yangtze) River. Due to the huge amount/of sediment load carried by the Changjiang River and emptying into the Lake, as well as to reclamation work carried out over past one hundred years, the lake surface area has reduced rapidly from 5,000 to 2,740 km2, thus deteriorating to a great extent the flood absorption and discharge capacity of the lake basin. Based on the data derived from the multi-date Landsat imagery, together with the field observation data and historical charts, some major issues concerning the origin of the Dongting Lake and its evolutional processes as well as its general tendency toward siltation are analysed in this paper.From a synoptical overview of the landsat imagery, it is apparent that the modern Dong-ting Lake network was derived from ponded lowlands within the flooded periphery of the Chang-Jiang River, as evidenced by the flood topography and the distribution of various surficial and buried crevass fans. The initiation of the water diverging scheme through four outlets of the Changjiang River in 1870 was a turning point in Dongting Lake’s evolutional history. The rapid progradation of deltaic deposits resulted in continuous migration eastwards and southwards of the Dongting Lake. The mode of lake siltation was mainly controled by the lake currents. The accretional cuspate sandbar system was formed in the East Dongting Lake with its source sediment supplied from the west and south inlets, and merged gradually with the deltaic accumulation from the Zhuzi River mouth, resulting in the segregation of the East Dongting Lake into numerous lake embayments as well as isolated inner lakelets varying in size. The siltation processes of the Dongting Lake reached its peak during a period from 1914 to 1955, with an average silting rate of 135 million cubic meters annually. The siltation processes were modified by the combined effects of many factors, among which the role of human activities in reclamation should not be overlooked. At this stage, according to the natural growth rate of the reedy sandbars fringing the lake-fronts it is predicted that the Dongting Lake might turn out to be a ri-verlet network in future. In order to protect the Lake from obsoletion, to maintain its present-level flood control capacity, it is suggested that effective measures be taken to control the four-outlet diverging process, to excavate flood discharge channels and to take full advantage of the existing inner lakelets and lowlands in establishing special flood diverging schemes.更多还原