1950—1990年期间永定河上修建了众多水利工程，如官厅水库、珠窝水库、三家店拦河闸等，这些水利工程在一定程度上满足了城市发展和居民生活的需要，保障了下游河段的安全，降低了洪水的可能性，但也导致了永定河流域生态环境的恶化。众多水利工程拦截了大量地表水，导致下游径流减少，直至断流；河性发生改变，河床出现粗化；地下水超采，地下水位埋深下降；土地沙化，形成沙源，风沙灾害加剧。永定河由多水变为缺水，由水灾为主变为风沙灾害为主。%During the period from 1950 to 1990, a lot of water conservancy projects, such as the Guanting Reservoir, the Zhuwo Reservoir, and the Sanjiadian Sluice Gate, were constructed on the Yongding River. These projects satisfied the demands of urban development and the residents’ livelihoods, guaranteed the safety of the lower reaches of the river, and eliminated the possibility of floods. However, they led to the degradation of the ecological environment in the Yongding River Basin. A large proportion of surface water was intercepted, resulting in the decrease of runoff downstream, until the river dried up. The nature of the river has changed and the riverbed has become rough. The groundwater has been over-exploited, resulting in a decrease in the depth to the water table. Land desertification occurred, forming a sand source, and sandstorm disasters intensified. Finally, the Yongding River has gone from having a high amount of water to having a shortage of water, and from being dominated by floods to being dominated by sandstorms.
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