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随着北京市区工农业生产发展,用水量也在不断增大。根据1956～1973年地下水动态资料,西郊地下水位平均每年下降0.5～1.0米,集中开采地区平均每年下降0.8～1.2米,个别地区下降达2.5米。同时,单井平均出水量亦在逐年衰减,如水源四厂1954和1971年比较生产井的单位出水量平均衰减50%左右。自1964年以来,先后在不同地段出现含水层衰竭现象。加之近二年的连续干旱和永定河放水量减少,西郊地下水位正在大幅度下降。这种下降进一步说明区域地下水的过量开采,也即开采量超过补给量,而开采过额部分是以消耗地下水储量作为补偿。1973年春西郊地下水径流量比1959年减少30%以上。北京市西郊地处永定河冲积洪积扇顶部地区,主要含水层系单一的砾卵石层,透水性
With the development of industrial and agricultural production in Beijing, water consumption is also increasing. According to the groundwater dynamic data from 1956 to 1973, the water table in the western suburbs dropped by an average of 0.5 to 1.0 meters per year. The average concentration of mining areas decreased by 0.8 to 1.2 meters per year on average, while that in some areas dropped by 2.5 meters. At the same time, the average single-well water discharge is also declining year by year, such as the Fourth Plant of Water Source 1954 and 1971 compared to production wells, the average unit water output decay of about 50%. Since 1964, aquifers have been depleted in different locations successively. Coupled with the continuous drought in recent two years and the reduction of water discharge in the Yongding River, the water table in the western suburbs is drastically declining. This decline further illustrates the over-exploitation of groundwater in the region, ie, the amount of recovery exceeds the recharge rate, while the over-exploitation is offset by the depletion of groundwater reserves. In the spring of 1973, the runoff of groundwater in the western suburbs dropped by more than 30% from 1959. The western suburbs of Beijing are located at the top of the Yongdinghe alluvial fan zone. The main aquifer is a single gravel layer with water permeability