石羊河流域地下水化学演变对水循环更新响应及模拟

Response of Groundwater Hydrochemical Evolution to Update of Water Circulation and Simulation in Shiyang River Basin

采用水文地质调查和水化学技术，通过对石羊河流域山前和中游武威盆地地下水的补径排关系及水化学模拟研究，探讨了该地区地下水化学演化规律对水循环更新的响应。研究结果表明，流域地下水从上游到下游矿化度逐渐升高，溶解性总固体（TDS）质量浓度在131～1750mg／L之间；水化学类型呈现明显分带特征，从HCO3^- SO4^2- Ca^2＋Mg^2＋型逐渐转换为SO4^2- HCO3^- Mg^2＋ Ca^2＋型。利用GIS软件中的Kriging空间插值方法对研究区1989--2009年TDS进行模拟，结果显示：在时间上，随着年份增加，盆地南部地下水TDS值由于降水和融水的冲释，呈减小趋势，中部先升高后下降；在空间上，自山口沿径流方向，TDS质量浓度逐渐增大。由于河流渗漏对地下水的补给作用，石羊河河床带TDS质量浓度明显偏低。地下水储水量和地下水埋深下降速率分别为3．04×10^83^3／a和0．47m／a。随着地下水位埋深的增大，TDS质量浓度呈减小趋势，降低速率在11．12～50．41mg／（L·a）之间。

Hydrogeological survey and geochemical technology were used to investigate the relationship among recharge, runoff and discharge and hydrochemical characteristics of the groundwater in the Wuwei basin of the Shiyang River. And the response of hydrochemical evolution law to water circulation update was discussed. The results indicated that the TDS （total dissolved solids） values were between 131 and 1 750 rag/L, gradually increasing along the flow direction. The hydrochemical types showed an obvious zonation from the upper reaches to lower, which gradually changed from HCO3^- -SO4^2-Ca^2＋-Mg^2＋ to SO24--HCO3^--Mg^2＋ -Ca^2＋. Kriging interpolation of GIS was used to simulate the variation of the TDS of the survey region from 1989 to 2009. The results showed that the TDS in the south basin gradually increased as time went by, while there was an increasing trend at the earlier years, followed by a drop in the north basin. The TDS increased gradually along the flow direction from the piedmont to tail. As a result of the runoff leakage supply to the groundwater, the salinity along the bank of the Shiyang River was significantly low. The formation cause of the chemical components of the groundwater was due to the dissolution of halite, plaster, dolomite and calcite, also influenced by evaporation, ion exchange and sedimentary. Decline rate of groundwater storage capacity and groundwater depth was 3.04 × 10s m3/a and 0.47 m/a, respectively. With the increase of groundwater depth, the TDS value showed a trend of decrease and the drop rate was between 11.12 -50.41 rag/（L·a）.