The Selenge River Basin occupies a total area of 447,000 km2, of which 343,000 km2 is located within Mongolia (the remainder is in Russia). The basin is characterized by an extreme continental climate, consisting of harsh, cold, dry winters and short, hot summers. Annual average temperatures are approximately -4°C and annual rainfall ranges from 220mm to 450mm. The major surface water resources in the basin include Hovsgol Lake, the Selenge, Orkhon and Tuul Rivers and the basin ultimately drains into Lake Baikal in Russia. The hydrogeology of the basin is varied and consists of a combination of alluvial deposits, Cambrian and Precambrian limestones, granites, sedimentary deposits and metamorphic rocks. The Selenge River Basin is a critical groundwater resource for Mongolia. Greater than 55% (~1.5 million) of Mongolia’s population resides within the basin and, during 2003, an estimated average of 700,000 m3/day of water was abstracted from the basin’s groundwater system. The basin services Mongolia’s largest cities and industries (including the rapidly expanding mining sector) as well as important traditional pastoral ranges. Recently created hydrogeological maps, coupled with topographical maps, have been used to identify both unconfined and confined groundwater resources within the basin. The total area of groundwater-bearing resources within the basin is estimated at approximately 280,000 km2, and while the volume of the resource has not been quantified; average recharge into the basin has been calculated at 5.6 x 109 m3/yr. It is believed that approximately 5% of the total annual recharge volume feeding into the basin is being utilized. However, due to the great spatial extent and irregularity of groundwater resources in the basin, coupled with the equally heterogeneous concentration of evolving landuses, some local aquifers near major centres are likely being overexploited, hence it is important to manage each sub-catchment individually within a greater overall management plan. Sustainable yields need to be determined to ensure maintenance of current groundwater levels and environmental flows for rivers, as well as providing a sustainable resource for continued utilisation. These need to be incorporated into management strategies at the international, regional and local level to ensure ongoing conservation of the resource and fair access for all stakeholders.