The reservoir area is located in the southwest of Jiaolai fault basin in Longdong uplift area, on the east side of Yishu fault zone, and at the junction of Jiaowei plain and hilly area in the middle reaches of Weihe River. Mostly hilly and sloping plains, the soil layer is clayey silt and loam, and the accumulation thickness is generally about 3 meters, and the bottom is clastic rock. The terrain in the reservoir area is high in the south and low in the north. The west bank of the reservoir is low hills, and the east bank is isolated hills. The flood control standard of Xiashan Reservoir is once in a thousand years, and the check standard is once in ten thousand years. The maximum discharge of spillway gate is18500m3 per second. Xiashan Reservoir Project consists of main dam, four auxiliary dams, spillway (sluice), spillway tunnel and hydropower station. The main dam is 2.75km long, the maximum dam height is 2 1m, and the crest width is 7 m. It consists of clay core sand shell dam and homogeneous earth dam. The auxiliary dams are located on the east bank of Weihe River, namely Nanxin auxiliary dam, Wulan auxiliary dam, Liujiagou auxiliary dam and Gong Zheng auxiliary dam, which are connected with hills and highlands respectively. It is a homogeneous earth dam with a total length of 28.88km, a crest width of 6m and an elevation of 44.0 ~ 44.7m.. The spillway is built between Xiashan and Xieshan. The overflow gate is 332 meters long, the elevation of weir crest is 28.83 meters, and there are 15 holes in the gate body, and the clear width of each hole is 16 meters. There are five drainage tunnels along the reservoir to supply water to the irrigation area, and the designed total water supply capacity is 138.9 m3/s. Xiashan Reservoir Hydropower Station has 9 units with a total installed capacity of 3475 kilowatts.