鄱阳湖圩区滞洪与水土资源利用协调

COORDINATION FORMS BETWEEN FLOOD DETENTION AND UTILIZATION OF WATER&SOIL RESOURCE WITHIN CIRCLED EMBANKMENTS IN LAKE POYANG

鄱阳湖区有圩堤564座,保护耕地近4200km2、人口720多万。圩堤对保护湖区人民生命财产安全起到了积极的作用,但有些圩堤占据了湖泊的正常行洪通道,给湖区防洪带来了不利影响,对这些圩区应当平圩还湖。还有些中小型圩区没有占据湖泊的正常行洪通道,但在洪水期间经常遭受洪水淹没,对这类圩区应根据实际情况实施“高水还湖滞洪,低水种植养殖”的运用方式,以缓解鄱阳湖区人多地少的矛盾。从洪水水力学基本理论出发,根据鄱阳湖洪水特征和圩区实际情况,定量分析了因中小圩区滞洪而降低湖水位的幅度、减少湖周边的淹没面积以及减轻湖区防洪压力,对鄱阳湖可滞洪中小圩区“高水滞洪,低水种养”的运用方式进行了探讨,提出了鄱阳湖不同规模的可滞洪圩区的滞洪启用水位和启用频率分别为:6.7km2以下圩区为21.65m与10%、6.7～33.3km2为22.05m与6.67%。建议采用自湖下游至湖上游的圩区滞洪启用次序,并对与滞洪需求相协调的圩区水土资源利用方式进行了初步研究。

There are564circled embankments in Lake Poyang,which protect agricultural field of about4200km 2 and more than7.2million residents.Although these embankments have had active effects in protection of residentials' daily life and properties,some of them have occupied the normal cannel for flood discharge in the lake,which has caused negative effects to lake flood control.The dykes of this kind should be moved off and the coordinate embankments should be returned to lake.Also,some embankments in Lake Poyang which don' t occupy the normal flood cannel are frequently inundated during flood seasons.These embankments may be exploited with the operation method of'flood detention during flood season but planting or breeding during low water level period'in order to copy with the problem of large population and with few agricultural fields.From the elementary theory of flood hydraulics and based upon actual circumstances of Lake Poyang,after having quantitatively analyzed the reduction of lake flood level,the diminution of inundated area near the lake shore and the lightening of social pressure for flood control due to the embankment flood detention,this paper discusses the embankment utilization forms of'flood detention during flood seasons and planting or breeding during low water level period'.It has been pointed out that the critical flood level for flood detention in embankments of different kinds and their flood detention frequency may be taken as:21.65m and10%for circled dykes of smaller than6.7km 2 ,but22.05m and6.67%for circled dykes of6.7~33.3km 2 .The sequence for starting flood detention has been recommended as the order from the lake outlet to the upper reach of the lake.Moreover,water and soil resource utilization forms,which coordinate with the requirements of flood detention,have also been studied in this paper.