Study area - The Kharaa River Basin
The Khaara River basin is located in northern Mongolia not far away from the capital Ulaanbaatar, between latitudes 47°53’ and 49°38’ N and longitudes 105°19’ and 107°22’ E, with a catchment area of 14,534 km2. The Kharaa River is 362 km long and has a mean long-term annual discharge (1990-2008) of 12.1 m3 s-1 at the outlet of the Kharaa river basin equivalent to a mean specific runoff of 0.83 l s-1 km-2.
The climate in the Kharaa basin can be characterized as dry winter continental, with mean annual temperatures oscillating around 0 °C. Therefore, the winters are typically very cold, long and dry, and mean monthly temperatures in January are ranging between minus 20 and minus 25 °C. In contrast, the short summers are warm to hot (with an average July temperature exceeding 15 °C), and the majority of the scarce precipitation falls between June and August. Mean annual precipitation in the Kharaa basin is ranging between 250 and 350 mm.
Several severe water quality problems occurred during recent years, several high risk areas have already been identified, and various ‘time bombs’ are ticking, sooner or later putting the drinking water supply of thousands of households as well as industrial water supply at risk. The major reasons for concern are twofold. First, toxic sludge from (insufficient) wastewater treatment of villages, cities, industry and mining activities is currently deposited with no or insufficient security measures (e.g. against leakage), often closely to surface waters or groundwater extraction sites. Second, insufficient treatment of water used in households, industry and mining is partly causing direct contamination of surface- and ground-waters. Because the availability of clean surface water resources is limited in the Kharaa catchment area, adequate ground water quality is fundamental to secure drinking water in human settlements in the basin. The Kharaa river basin has numerous spots were contamination of ground water mainly from mining activities have occurred in the past.