Groundwater quality under stress: contaminants in the Kharaa River basin (Mongolia)

Groundwater quality in Mongolia is increasingly endangered by expanding mining and industrial activities, urbanization and intensified land-use for agriculture. In the framework of the research project Integrated Water Resources Management in Central Asia: Model Region Mongolia (MoMo) project, groundwater and surface water quality has been monitored since 2007 throughout the Kharaa River basin, which includes the second largest city of Mongolia, Darkhan. In order to investigate the potential impacts of human activities, groundwater samples have been collected at 40 locations and were analyzed for heavy metals, electrical conductivity, chloride and boron. The initial characterization of all groundwater bodies in the river basin was an important prerequisite for the assessment of groundwater quality. Our results show impacts especially in the lower and middle reaches of the Kharaa River basin including the city of Darkhan and the smaller towns Khongor, Salkhit, Zuunkharaa and Baruunkharaa. Particularly in Khongor, significantly high values of electrical conductivity, chloride and boron were detected, indicating serious pollution by domestic and industrial wastewater. Furthermore, elevated concentrations of heavy metals, especially arsenic, lead, zinc, nickel, iron and manganese, were found in the vicinity and downstream of mining areas whereby in some cases the maximum contaminant level of the Mongolian drinking water guideline was exceeded. The findings of this study illustrate explicitly the stress on groundwater quality and its vulnerability in the Kharaa River basin. A sustainable water resources management needs to be urgently implemented to avoid potential public health impacts.