对三峡工程建成后长江中游防洪形势的新认识

长江上游穿行于深山峡谷间，出宜昌就进入广阔的平原地区。长江中游地区江面宽展，两岸全靠堤防约束江水，河道的安全泄洪能力远小于巨大的洪水来量，且两岸地面高程普遍低于洪水位数米至十几米，是长江流域洪水灾害最为集中、最为频繁的地区。2003年长江三峡大坝第三次截流后，上游地区的水文环境也将产生许多变化，与建库前相比洪峰时间提前、洪峰量增加、洪峰预见期缩短。三峡工程建成后，可减轻长江上游特大洪水或以长江上游洪水为主的全流域性洪水灾害，对于长江中游地区的洪水也有一定的调控影响,但防洪形势仍十分严重。

A NEW PERSPECTIVE ON THE SITUATION OF FLOOD PREVENTION IN THE MIDDLE REACHES OF THE CHANGJIANG RIVER AFTER THE COMPLETING OF THE SANXIA DAM

This article analyses the change of the hydrological environment in the upper reaches of the Changjiang River, after the completing of the Sanxia Great Dam, and it points out the changes of environment which can be summarized as follows: flood quantity concentrates;the height of flood peak increase; the time of flood peak reduces The article also indicates that the situation of preventing flood is still very severe in the middle reaches of the Changjiang River, especially the river section from jianli county to Wuhan city and the major branch dykes of Dongtin Lake in the South Jingzhou district