Groundwater Availability and Renewal in Inner Mongolia, China: the Minqin Basin and the Badain Jaran

摘要

This paper examines the sources of recharge to groundwater as well as the timing of recharge in two contrasting areas-the Badain Jaran and the Minqin Basin. The amount of direct recharge has been estimated using chemical and isotopic techniques. Unsaturated zone profiles are also used to determine the history of recharge. Modern recharge is around 2mm yr~(-1), determined using unsaturated zone profiles and chloride mass balance. A small component of modern, presumably river-derived, groundwater is identified in parts of the basin from tritium ~3H-~3He. A clear distinction is found between modern waters with median δ~(18)O values of (6.5±0.5)/1000 and most groundwaters in the basin with much depleted isotopic values. Radiocarbon values as pmc range from 0.6% to 85% modern, indicating late Pleistocene and Holocene ages for recharge. The geochemical evidence suggests that groundwater underlying the desert is hydraulically continuous and is part of a regional flow system. In the Badain Jaran, the present day recharge is negligible-around 1mm/yr. Stable isotope ratios (δ~(18)O and δ~2H) show that modern recharge differs significantly from the regional aquifer (which gives rise to lake system) and it is suggested that the deeper resource is also of Late Pleistocene in age and also part of a regional flow system. The implications of these results for management of water resources in north-west China are discussed since current management is quite unsustainable.