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三峡工程正常蓄水水位175 m时,洛碛镇水位达175.5 m,5年一遇洪水位为176.5 m,20年一遇洪水位为180.7 m,百年一遇洪水位为184.9 m。洛碛镇长江高漫滩地表高程低于183 m,属三峡工程浸没区,库区回水形成的浸没现象普遍。本文通过对洛碛镇地层结构和水文地质条件进行分析,结合历史监测资料,建立回归方程和三维非稳定流地下水流系统,采用常规方法和三维数值模型预测回水后洛碛镇地下水雍高,确定浸没范围及相应程度,为地质环境保护策略提供依据。研究表明,研究区为上下两层地下水位的二元结构,上层水位高于下层水位;库水位保持在175.5 m的时间为41 d,上层地下水从175.5 m壅高的总时间为58 d;数值模拟计算结果能较好的匹配地下水壅高实测值;库水位175.5 m时,浸没区面积为0.386 8 km2。
When the normal water level of the Three Gorges Project is 175 m, the water level in Laoxia Town reaches 175.5 m, the water level at once in five years is 176.5 m, the once-in-20-year flood level is 180.7 m, and the once-in-hundred-year flood level is 184.9 m. The surface elevation of the high floodplain in Luojian Town is below 183 m, which belongs to the submerged area of the Three Gorges Project. The submergence phenomenon formed by the backwater in the reservoir area is widespread. In this paper, through analyzing the stratigraphic structure and hydrogeological conditions in Luoyang town, combining with the historical monitoring data, establishing the regression equation and the three-dimensional unsteady groundwater flow system, the conventional method and three-dimensional numerical model are used to predict the groundwater of Laoxian Town, Determine the immersion range and the corresponding degree, provide the basis for the strategy of geological environment protection. The study shows that the study area is the binary structure of the groundwater level in the upper and lower levels, the water level of the upper level is higher than that of the lower level, the total time for the reservoir water level to remain at 175.5 m is 41 days and the upper groundwater from 175.5 m 壅 to 58 d. The simulated results can well match the measured groundwater table height; when the reservoir water level is 175.5 m, the submerged area is 0.386 8 km2.