玛纳斯河流域山前平原地下水水化学特征与补给来源

Hydrochemical characteristics and recharge of groundwater in piedmont plain in the Manas river basin

山区-山前平原地下水是干旱区重要的供水水源,以西北玛纳斯河流域为例,利用水化学和环境同位素示踪,揭示了山前平原地下水水化学特征与补给来源及其局部差异的原因。结果表明:山前平原地下水多为HCO_(3)·SO_(4)-Ca、HCO_(3)·SO_(4)-Na·Ca型水,TDS介于300mg/L左右,水化学特征的局部差异受控于不同的地下水径流条件,玛纳斯河西岸更有利的径流条件形成了较东岸TDS平均偏低100~150mg/L的地下水。水化学组分主要受岩石风化控制,以硫酸盐、岩盐的溶解以及碳酸盐的溶解-沉淀和阳离子交换为水岩相互作用的主要过程。氢氧稳定同位素结果指示山前平原地下水主要接受山区大气降水形成的地下水及河水的侧向径流补给,补给受蒸发影响不强烈,不同季节和补给形式的降雨是同位素差异的主要原因。西岸地下水主要接受冬季降水补给,补给形式以山区河水为主,东岸地下水受夏季降水的补给比例更高,山区河水、地下水的共同补给为主要形式。

Groundwater in the mountainous-piedmont plain is an important source of water supply in arid areas.Taking the Manas river basin as an example,the hydrochemical characteristics and recharge sources of groundwater in piedmont plain and the reasons for local differences were revealed by hydrochemistry and environmental isotope tracer.The results show that groundwater in the piedmont plain is dominated by HCO_(3)·SO_(4)-Ca and HCO_(3)·SO_(4)-Na·Ca type with TDS of about 300 mg/L.Local differences in hydrochemical characteristics are controlled by different groundwater runoff conditions,more favorable conditions in the west bank of Manas river resulted in an average TDS of 100~150 mg/L lower than that in the east bank.The groundwater chemical composition is controlled by rock weathering,and the dissolution of sulfate and rock salt,dissolution and precipitation of carbonate and cation exchange are main processes of water-rock interaction.The stable isotope results indicate that groundwater in the piedmont plain are mainly recharged by groundwater and rivers lateral runoff from mountain meteoric precipitation,and is not strongly influenced by evaporation.The rainfall in different seasons and recharge forms is the main reason for the differences of isotopes.Groundwater in the west bank is mainly recharged by winter precipitation in the form of mountain rivers,while recharged by summer precipitation in the form of mountain rivers and groundwater in the east bank.