MODELING WATER AND NITROGEN DYNAMICS AT 3 DIFFERENT SPATIAL SCALES - INFLUENCE OF DIFFERENT DATA AGGREGATION LEVELS ON SIMULATION RESULTS

The effect of different data qualities (different data aggregation lev els) on the results of an integrated simulation model on soil water an d nitrogen dynamics is investigated for an area of 3 communal district s which were part of a former large scale study on nitrogen losses. Di saggregated data from this regional scale study are compared to the re al situation within the regarded area. Results of groundwater recharge and nitrogen leaching indicate that the aggregation of soil map units has a relative small effect compared to the averaging of weather data and to errors of land use. The use of average data derived from long term weather observations lead to a clear underestimation of groundwat er recharge. Nitrogen uptake by plants in the regional study is often less than simulated with the real weather data and the observed rotati on. Both result in higher nitrogen losses by leaching in the regional study although the water flux is less.