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 nutrient emissions into river basins, various point and diffuse pathways,
as well as nutrient load in rivers, could be analysed. Despite 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 shows 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 a 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 economic 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 for water quantity and quality. The model MONERIS allows the assessment
of measures which are inevitable to protect the water quality under shrinking water availability.