Mesoscale Modeling Of Nitrate Pollution Of Rivers By Groundwater

A multi-compartment model is applied at the mesoscale to simulate the spatially differentiated nitrate pollution of rivers by groundwater in a test area of 800 km(2) in the northern part of Saxony. Both nitrate influx and discharge processes are considered. Mass transport is represented by applying a multiple flow direction algorithm to the groundwater velocity field of an upper aquifer which is assumed to be continuous in the test area. In total, about one tenth of the nitrate surplus of soils discharges into the rivers of the test area along groundwater flowpaths. In particular, farming areas within 3 km of the rivers emit large amounts of nitrate. The simulations carried out with the compartmentalized approach allow to check model results and to adapt them to average discharge and quality data determined at surface water gauges. They show that the model reflects the average measurement values reasonably well by accounting for the basic hydrogeological conditions.