退田还湖对鄱阳湖洪水调控能力的影响

利用实测资料统计了鄱阳湖近50年来湖盆形态和洪水水情的变化，表明由于围垦的作用，1954~1992年鄱阳湖面积共减小1 300 km2，容积共减少81×108 m3，调节系数从17.3%下降到13.7%，调洪能力降低20.8%；20世纪90年代与50年代相比，年最高水位平均值抬高1.80 m。计算了退田还湖对近50年来两次特大洪水（1954年洪水和1998年洪水）最高水位的效应值，表明分别可使1954年洪水和1998年洪水的最高水位降低0.72 m和0.68 m。估算了退田还湖对鄱阳湖洪水位频率的影响，表明50年一遇和100年一遇的洪水位分别可降低0.63 m和0.68 m。计算还表明，高水还湖（单退）降低洪水位的作用与圩区还湖前夕的内涝程度密切相关，说明及时排除圩区的内涝对保障退田还湖的防洪减灾作用至关重要。分析了退田还湖面临的主要问题，分别是高水还湖圩区的内涝问题和平垸行洪（双退）圩区的血防问题；探讨解决这两个问题的具体对策，分别为单退圩堤采用“限高加固，排空待蓄”的运作方式，双退圩堤采用“敞开进洪，兼顾血防”的运用方式。

IMPACT OF RESTORING LAKE BY STOPPING CULTIVATION ON FLOOD CONTROL CAPACITY OF POYANG LAKE

This article used the actual database to count the change in shape of lake basins and in the flood of Poyang Lake in 50 years. It is indicated that because of reclamation, the lake area experienced a reduction of 1 300 km2 during the period from 1954 to 1992, and the volume had a reduction of 81×108 m3, with the regulating coefficient dropped from 17.3% to 13.7% and regulating flood ability reduced by 20.8%. When comparison was made between 1990s and 1950s, the average value of annual maximum high water raised 1.80 m. It was also calculated that the maximum high water level by means of restoring lake area from cultivation would be reduced by 0.72 and 0.68 m, respectively in two serious flooded years, i.e. 1954 and 1998. The restoration may also have some influence on the frequency of flood levels in Poyang Lake, a 0.63 m and a 0.68 m reduction in maximum high water level may be expected in one chance flood within 50 years and one chance flood within 100 years, respectively. It is also indicated that restoring lake from cultivation at high water level, the so called semi restoration can reduce the flood level, and is closely related with waterlogging degree before restoration. Major questions in relation to lake restoration by stopping cultivation are: waterlogging capacity in dike areas when restoration was taken at high water level, and schistosomiasis problem in turning over dykes for flood area, the so called complete restoration. The countermeasure to solve these two problmes are: “limiting the high and reinforcement, evacuating for gathering” in semi restoration dikes and “opening to discharge the flood, pay attention to the cure of schistosomiasis” in the double draws back dike.