Peter Kreins

Model based impact analysis of policy options aiming at reducing diffuse pollution by agriculture—a case study for the river Ems and a sub-catchment of the Rhine

Abstract In this paper an integration of the agricultural economic model RAUMIS with the hydrological models GROWA98 and WEKU is presented. The focus lies on an area wide, regionally differentiated, consistent link-up between the indicator “nitrogen balance surplus” and nitrogen charges into surface waters. The model network is used to analyze the status quo situation in the year 1999 for two river catchments in Germany that feature very distinct natural and socio-economic conditions. Regarding agriculture, the study areas include regions with specializations in cash crops, in intensive livestock featuring high nitrogen surplus, and extensive livestock production on permanent grassland. Due to regionally varying hydrological conditions quite different shares of agricultural nitrogen surpluses ranging from 25 to 92% enter surface waters. Furthermore, impacts of alternative nitrogen reduction measures namely a limitation of livestock density and a tax on mineral nitrogen are quantified. Measures of the nitrogen reduction potential and costs in terms of agricultural income forgone are taken into account in the assessment. Results regarding the effects of restricting the livestock density or tax mineral nitrogen highlight that the mitigation of diffuse water pollution problems requires regionally tailored measures.

Multispectral remotely sensed data in modelling the annual variability of nitrate concentrations in the leachate

The advantages of using multispectral remotely sensed data instead of CORINE Land Cover for the modelling of nitrate concentrations in the leachate of the Rur catchment are presented and discussed in this paper. In this context it has been shown that the identification of main crops and annual crop rotation in the Rur catchment by SPOT, LANDSAT and ASTER imagery provides the key for a spatial and thematic enhancement of the model results. The spatial resolution of the nitrogen surplus data set which denotes the linkage between RAUMIS and GROWA is enhanced from district level to field/pixel level. In parallel, the empirical water balance model GROWA is enhanced to differentiate between agricultural crops in the real evapotranspiration calculation. It is calibrated by runoff data measured at gauging stations. Results indicate, e.g., an average nitrate concentration in the leachate of 42mg NO3/L in the relatively wet year of 2002 and almost 62mg NO3/L in the dry year of 2003. There is a 20mg NO3/L weather-induced difference which can be modelled in a more detailed way using self-processed remotely sensed data. The model results were compared to nitrate concentrations observed in the top parts of multi-level wells. In this way the related coefficient of determination has been improved from a value (R) of -0.50 using CORINE to 0.59 by using self-processed remotely sensed data, thus demonstrating the potential of the enhanced model system.

Quantification of Climate Change Impact on Regional Agricultural Irrigation and Groundwater Demand

Climate change is expected to impact agricultural production conditions and groundwater resources. The climate change impacts are expected to be of particular importance for the German region North Rhine-Westphalia. Due to a high population density and intensive partial irrigation of agricultural production, future resource conflicts for groundwater are expected. An integrated model framework consisting of climate, crop-soils and groundwater models represents the regional heterogeneous climatic, geographic and agronomic conditions. The integrated model framework simulates the irrigation demand and groundwater recharge. An ex-post comparison between the simulated reference period (1961 to 1990) and statistical data prove a good model validity. The climate change scenario for the future period 2051 to 2080 assumes decreasing precipitation and increasing transpiration. The simulated total irrigation demand increases by nearly 20 times compared to the reference period (1961 to 1990) and increases regionally to more than 40xa0mm/ha. Decreasing groundwater recharge results in a tenfold increased share of irrigation water from groundwater. This share accounts regionally for more than 30xa0%. The results indicate important impacts for both agricultural production and other groundwater users.

Forecasting the effects of EU policy measures on the nitrate pollution of groundwater and surface waters

We used the interdisciplinary model network AGRUM [corrected] to predict the actual mean nitrate concentration in percolation water at the scale of the Weser river basin (Germany) using an area differentiated (100 m x 100 m) approach. AGRUM [corrected] combines the agro-economic model RAUMIS for estimating nitrogen surpluses and the hydrological models GROWA/DENUZ for assessing the nitrate leaching from the soil. For areas showing predicted nitrate concentrations in percolation water above the European Union (EU) groundwater quality standard of 50 mg NO3-N/L, effective agri-environmental reduction measures need to be derived and implemented to improve groundwater and surface water quality by 2015. The effects of already implemented agricultural policy are quantified by a baseline scenario projecting the N-surpluses from agricultural sector to 2015. The AGRUM [corrected] model is used to estimate the effects of this scenario concerning groundwater and surface water pollution by nitrate. From the results of the model analysis the needs for additional measures can be derived in terms of required additional N-surplus reduction and in terms of regional prioritization of measures. Research work will therefore directly support the implementation of the Water Framework Directive of the European Union in the Weser basin.