论文部分内容阅读
永定河是海河五大支流之一,位于北纬40°附近,流域内城市存在西、北、东三个子系统,中心地分别是大同、张家口、北京(京津),明清以来北京作为国家政治中心,享有资源优先聚集权,张家口、大同则以“京师屏障”、服务京师为主要职能,从军事屏障、经济屏障到近年的生态屏障,很少顾及上游地区环境特征及可能引致的流域性变化。600多年来随着上游桑干河、洋河流域灾害类型增多、频次增加,下游京津水环境问题与之同步,20世纪中期以来流域性水问题由洪灾逐步转向了日趋严重的水资源短缺。
Yongding River is one of the five major tributaries of the Haihe River and is located at a latitude of 40 ° north latitude. There are three subsystems in the basin, namely, the west, north and east. The centers are Datong, Zhangjiakou and Beijing (Beijing-Tianjin) respectively. Since the Ming and Qing Dynasties, Beijing has been the national political center , Zhangjiakou and Datong are using the “capital barrier” to serve the capital as the main function. From the military barrier and economic barrier to the ecological barrier in recent years, they seldom take into account the environmental characteristics of the upper reaches and the possible watershed Variety. In the past 600 years, with the increase of the types of disasters in the Sanggan River and the Yanghe River basin and the increase of the frequency, the water and environmental problems in the lower reaches of Beijing and Tianjin have been synchronized with each other. Since the mid-20th century, the problem of sexual water in the basin has shifted from flood to increasingly serious water shortage.