MODELING IMPACTS OF LAND-USE CHANGE AND CLIMATE-CHANGE ON NITRATE-NITROGEN IN THE RIVER DON, NORTH-EAST SCOTLAND

The river quality model QUASAR (Quality Simulation Along Rivers) has b een applied to the River Don system in North East Scotland. This mass balance model for nitrogen has been used to estimate the impacts of la nd use change and climate change on river water quality. Changing agri cultural patterns have been simulated and indicate increased nitrogen levels in the river as catchment land use changes. Climate change will alter flow regimes, temperature and nitrogen mineralization patterns. Simulation runs for a range of scenarios illustrate the impacts of cl imate change with the most significant effect being mineralization of nitrogen in the soil feeding through into the river system. These high er nitrogen levels are reduced slightly by the increased temperatures and decreased summer hows, both of which enhance denitrification proce sses.