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Abstract: Multiple isotopic and hydrogeochemical tracers were utilized to understand the recharge sources and geochemical evolution of groundwater in the Quaternary aquifer beneath Jinchang city and the adjacent Gobi desert area. The groundwater shows markedly depleted stable isotopic composition compared to modern rainfall. The signature of groundwaters from Jinchang and the northern Gobi desert area differ clearly from that of the alluvial fan in the south Yongchang basin and modern rainfall, and has lower or non-detectable 3H activity, implying that the aquifer is likely maintained by palaeowater. This groundwater in the Gobi desert has a 14C age older than 12ka, indicating that the groundwater resources are non-renewable. The build-up of dissolved solids through evaporation is a major control on groundwater composition, and the dominant anion species change systematically from , to Cl−, but cations from weathering of albite, calcite, dolomite and gypsum also make a significant contribution. The scientific results have important implications for groundwater management in Jinchang city and as well as in the Shiyang River basin under China’s West Development Strategy. It is recommended that the water allocation program of diverting water from the Dongda river to the Minqin basin be reconsidered. [Copyright &y& Elsevier]

Summary: Multiple isotopic and hydrogeochemical tracers were utilized to understand the limits to recharge from Tibetan plateau to Gobi desert. The average direct recharge rate according to chloride mass balance is between 0.9–2.5mmyr−1 based on an annual rainfall of 120mmyr−1, indicating that this has negligible impact on groundwater. The groundwater shows markedly depleted stable isotopic composition compared to modern rainfall. The signature of groundwaters (around −10.4‰ to −9.6‰ δ18O in several wells) from Dajing and South Lake playa differ clearly from that of the alluvial fan and modern rainfall, and has lower or undetected tritium activity, implying that the aquifer in the desert is maintained by palaeowater. This groundwater has an estimated 14C age of ∼4kyr, with a recharge temperature of 7.3°C. At current hydraulic head gradients, transit time from the recharge zone (Wuwei-Gulang alluvial fan) to South lake is approximately 2200–3500 yrs, indicating that groundwater flow is relatively slow and that the water resources are non-renewable. The geochemical information is comparable to the isotopic results of limit recharge sources of groundwater from Tibetan plateau to the Gobi desert. The buildup of dissolved solids through evaporation is a major control on groundwater composition, and the dominant anion species change systematically from to Cl−, but the dissolved ions from albite, calcite, dolomite and gypsum also have a significant contribution. It is advised to re-consider seriously the immigration policy of South lake to meet the groundwater management in the mountain front to Gobi desert. [Copyright &y& Elsevier]