Groundwater Recharge Source In Badain Jaran Desert: Evidence From Environmental Isotopes

Based on isotopes, geochemistry, hydrogeology and palaeoclimate, the following results can be obtained.Firstly, the Local Meteoric Water Line(LMWL) in west of China isδ²H = 7.56δ¹⁸O+5.05 (‰VSMOW) using the data from GNIP(IAEA and WMO). The Hydrogen and Oxygen Isotope Effect was analyzed in this region. The Temperature Effect is most important effect toδ¹⁸O andδ²H in precipitation and their value is 59.9% and 57.0% respectively. The next important effect is rainfall mount.The relationship between groundwaters and lakes are drainage type, flow type and drainage-flow type. The meteoric water line in Badain Jaran Desert and Gurinai isδ²H= 7.77δ¹⁸O+7.56 (‰VSMOW). The average oxygen isotope in precipitation in the Desert is -7.3‰using isotope latitude effect. Groundwaters in the desert have undergone intense evaporation in low humidity. The evaporation line intercept against meteoric water line is -11.4‰, which is about 4‰depleted from modern rainfall. The intercept is similar withδ¹⁸O in groundwater in subregion of radiocarbon age of 10-40ka. It is concluded that the groundwater in Badain Jaran Desert was recharged in cold and wet climate condition from 10-40ka or more early. That meant there was less evaporation and water quality was better than modern groundwater in Yabulai. As millennium scale climate became warm and dry, less precipitation and high evaporation happened. The groundwater level has been declining and lake becoming smaller.The geochemistry processes of groundwater in the desert are silicate dissolution, gypsum dissolution, carbonate precipitation and cation exchange. Using inverse modeling, Yabulai groundwater quick recharge was denied while rainfall may one of recharge sources, regardless of modern rainfall or palaeorainfall. According to Darcy's Law and hydrogeology, the groundwater level has declined with the velocity is 11.8mm/a (11.8m/ka), which fits to the palaeolakebank and the investigation.