Distinct groundwater recharge sources and geochemical evolution of two adjacent sub-basins in the lower Shule River Basin, northwest China

Wang, Liheng; Dong, Yanhui; Xie, Yueqing; Song, Fan; Wei, Yaqiang; Zhang, Jiangyi

Distinct groundwater recharge sources and geochemical evolution of two adjacent sub-basins in the lower Shule River Basin, northwest China | Différentes origines de la recharge d’aquifère et évolution géochimique de deux sous-bassins adjacents du bassin inférieur de la rivière Shule, nord-ouest de la Chine Distintas fuentes de recarga y evolución geoquímica del agua subterránea en dos sub-cuencas adyacentes en la parte baja de la Cuenca del Río Shule, noroeste de China 中国西北疏勒河流域下游两个相邻次级盆地地下水补给来源及地球化学演化差异 Fontes distintas de recarga e evolução geoquímica das águas subterrâneas em duas sub-bacias a jusante da Bacia Hidrográfica do Rio Shule, noroeste da China

2016

Based on analysis of groundwater hydrogeochemical and isotopic data, this study aims to identify the recharge sources and understand geochemical evolution of groundwater along the downstream section of the Shule River, northwest China, including two sub-basins. Groundwater samples from the Tashi sub-basin show markedly depleted stable isotopes compared to those in the Guazhou sub-basin. This difference suggests that groundwater in the Tashi sub-basin mainly originates from meltwater in the Qilian Mountains, while the groundwater in the Guazhou sub-basin may be recharged by seepage of the Shule River water. During the groundwater flow process in the Tashi sub-basin, minerals within the aquifer material (e.g., halite, calcite, dolomite, gypsum) dissolve in groundwater. Mineral dissolution leads to strongly linear relationships between Na⁺ and Cl⁻ and between Mg²⁺+ Ca²⁺ and SO₄ ²⁻ + HCO₃ ⁻, with stoichiometry ratios of approximately 1:1 in both cases. The ion-exchange reaction plays a dominant role in hydrogeochemical evolution of groundwater in the Guazhou sub-basin and causes a good linear relationship between (Mg²⁺+ Ca²⁺)–(SO₄ ²⁻ + HCO₃ ⁻) and (Na⁺+ K⁺)–Cl⁻ with a slope of −0.89 and also results in positive chloroalkaline indices CAI 1 and CAI 2. The scientific results have implications for groundwater management in the downstream section of Shule River. As an important irrigation district in Hexi Corridor, groundwater in the Guazhou sub-basin should be used sustainably and rationally because its recharge source is not as abundant as expected. It is recommended that the surface water should be used efficiently and routinely, while groundwater exploitation should be limited as much as possible.

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