环境同位素方法在平凉市岩溶地下水研究中的应用

应用环境同位素方法对平凉隐伏岩溶水的研究结果表明 ,研究区隐伏岩溶水形成较早 ,且有大量现代水的混入 ,平均混入量为 5 4 %。说明研究区隐伏岩溶水的补给和更新能力较好。环境同位素分析结果还显示 ,大岔河隐伏岩溶水为一相对独立、半开放的水文地质单元。其补给来源部分为流域内大气降水、地表水的补给 ,部分为东南部三道沟岩溶地下水的补给。根据环境同位素 EPM与 EM两种模型计算 ,地下水的滞留时间为 36 a。地下水储存量为 1.314× 10 8m3;储水系数为 7.2 9× 10 - 3。这一结果与传统勘探方法的计算结果基本吻合 ,说明环境同位素方法的实用性 ,可在地下水资源调查中作为传统方法的补充和对比。

Application of the Environmental Isotope Technique to the Study of Karst Groundwater in Pingliang City

An example is given for the application of the environmental isotope technique to interpreting recharge mechanisms and renewal ability evaluation of covered karst aquifer in semiarid, NW China. Based on isotope analysis, the Ordovician carbonate rocks aquifer in the study area mainly originated from direct infiltration of atmospheric water in carbonate outcrops in the Sandao and Dazha valleies. Stable isotopes show that the karst groundwater in the Dazha valley seems to be recharged in a catchment area with a mean elevation of 1685~1854 m. The temporal evolution of stable isotopes, tritium content and hydrochemistry show the existence of an interconnection between Dash and Sando Ordovician limestone. The isotopic composition also shows that the groundwater in Ordovician limestone is a mixture of old groundwater and modern recharge of local infiltration. The mean percentage of the modern water accounts for 54%, which is found usually at intensively fractured areas suggesting good renewal ability of aquifers. Based on the EPM and EM models, the mean turnover time of the groundwater in the Ordovician carbonate rocks was evaluated to be 36 years. On the basis of this evaluation, the size of the groundwater reservoir and the mean storage coefficient have been calculated to be 0 134 billion m3 and 0 0073 respectively.