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Within the framework of Integrated Water Resources Management (IWRM) the
nutrient and heavy metal levels within the Kharaa river basin were investigated. By the application
of the MONERIS model, which quantifies nutrients emissions into river basins, various point and
diffuse pathways, as well as nutrient load in rivers could be analyzed. Despite of seasonal
variations and inputs of point sources (e.g. Wastewater Treatment Plant Darkhan) the nutrient
concentrations in most of the subbasins are on a moderate level. This show evidence for a nutrient
limited ecosystem as well as dilution effects. However, in the middle and lower reaches heavy
metal concentrations of Arsenic and Mercury, which are linked to mining activities in many cases,
are point of concern. Thus measures are necessary to protect the valuable chemical and ecological
status of the Kharaa river and its tributaries. As a result of the growing economical pressure
Mongolia will enhance the agricultural production by irrigation. Until 2015 about 60 % of the
agricultural land shall be irrigated. In addition the gold mining activities shall increase by 20% a
year. Both sectors have a high demand to water quantity and quality. The model MONERIS allows
the assessment of measures which are inevitable to protect the water quality under shrinking water
availability.
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