以库计水源地地下水为研究对象，在分析研究区水文地质条件的基础上，系统研究了研究区地下水的水化学时空变化特征：从外围分水岭向内以及由内部分水岭向周边，地下水水化学类型总体上沿地下水流向，呈HCO₃型→HCO₃•Cl型→HCO₃•SO₄•Cl型→SO₄•Cl型逐步过渡变化规律；在垂向上，中、浅层地下水水力联系较为密切，分带规律不明显，深部地下水水质略差；在时间上，由于白垩系含水层厚度巨大，垂向水力联系密切，且水位埋藏普遍较深，季节性变化对地下水水质影响有限，地下水水质相对稳定。

On the basis of analyzing hydrogeological conditions, the spatio-temporal variation of hydrochemical characteristics of groundwater in Kuji water source area of Ordos basin is systematically researched. The chemical composition, spatial distribution, and variation of hydrochemical type were affected by geographic, geomorphic and runoff conditions. Results showed that hydrochemical type changed as a whole along the direction of groundwater flow from  the peripheral watershed towards the interior and from the internal watershed towards the peripheral. The main negative ion gradually changed from HCO₃ to HCO₃•Cl and further HCO₃•SO₄•Cl, and then SO₄•Cl. In vertical direction, close hydraulic connection between the middle layer and shallow layer groundwater was found, and their partition was not obvious. Due to close hydraulic connection in vertical direction for Cretaceous aquifer of huge thickness and the depth of groundwater, the groundwater quality is less affected by seasonal change.