宜昌市主城区浅层地下水的赋存特征初探

Occurrence Characteristics of Shallow Groundwater in Urban District in Yichang

宜昌市主城区浅层赋存的松散砂卵石孔隙水、碎屑岩裂隙水、砾岩裂隙水、碳酸盐岩裂隙岩溶水,以潜水为主,局部弱承压。地下水位埋深0.50~29.86 m,平均埋深5.63 m。地下水位标高39.00~120.00 m,平均标高72.93 m。地下水水力梯度一般0.16~0.004,平行长江方向、地势低平地段地下水水力梯度较小,垂直长江方向、地势起伏较大地段地下水水力梯度较大。地下水位在丰水期较平水期升高0.50~8.25 m,水位变化主要受季节性大气降水影响。松散砂卵石孔隙含水层与奥陶系南津关组灰岩裂隙岩溶含水层富水性弱—中等,白垩系五龙组砂岩夹泥岩裂隙含水层与石门组砾岩裂隙含水层富水性弱,可视为相对隔水层。区内雨量充沛,浅层地下水循环强烈,地下水多为重碳酸型。

According to the void type of water bearing rock,the underground water in the main urban area of Yichang,Hubei Province can be divided into 4 types:pore-water in loose sand and pebble,crevice-water in clasolite,conglomerate and karst water in fracture of carbonate rock.There are phreatic water primarily and confined water partly.The groundwater level range from 0.50 to 29.86 m and it is 5.63 m that average value of the groundwater level.The elevation of groundwater level range from 39.00 to 120.00 m and the average value of elevation is 72.93 m.The hydraulic gradient ranges from 0.16 to 0.004.The groundwater hydraulic gradient is smaller in the areas with low and flat and parallel to the Yangtze River.Vice versa,the groundwater hydraulic gradient is larger in the areas perpendicular to the Yangtze River and the areas with much rise and fall.The variation of groundwater level is mainly affected by seasonal precipitation.The groundwater level increases by 0.50 to 8.25 m in wet season compared with that in normal season.The water abundance of aquifer that pore-water in loose sand and pebble and crevice-water in Ordovician Nanjinguan clasolite is weak to medium and that fissured water-bearing stratum in Cretaceous Wulong formation sandstone with mudstone and Shimen formation conglomerate is weak which can be regarded as aquiclude.The area has abundant rainfall,strong circulation of shallow groundwater and most of the groundwater is bicarbonate type.