UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH October 2004 in Leipzig, Germany at the UFZ Centre for Environmental Research 11 th Magdeburg Seminar on Waters in Central and Eastern Europe Uncertainties in the mesoscale modelling of water and nitrogen fluxes u The project: “Water and nutrient fluxes in the loess region in the Elbe catchment as a basis for sustainable land use” u German Ministry of Education and Research: “Ecological research in the riverine landscape of the River Elbe” (No )

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Study area: km² - loess region

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Problem Bad Düben river gauge

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Aim To find a way of quantifying nitrogen inputs - via their discharge pathways km²  mesoscale investigation

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH

Aims To find a way of quantifying nitrogen inputs - via their discharge pathways - mesoscale investigation To quantify the error rate of the results (input data) sensitivity analyses: - total runoff - nitrogen losses

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH ABIMO Climate values precipitation P o = 1.09 * P 1 max. evapo- transpiration acc. to TURC [36] ET 1.1*TURC Land use Agriculture Forestry Non-vegetated land Sealed area Soil type (effective field capacity) Sand Silt Loam Clay Peat Groundwater level Irrigation Mean effective root depth TW Rise elevation TA = TG- TW Capillary rise rate CR TG B Establishment of efficiency parameters x PKRB ET o TURC   11.* n = 0.11 n B = 1.5 * n BAGROV relation y = ET a / ET 1.1*TURC Actual evaporation ET a = y * ET 1.1*TURC Total flow R and groundwater recharge rate GWR R = P o - ET a P o 1.1*TURC

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Sensitivity analyses

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Sensitivity analyses

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Sensitivity analyses

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Alternative calculations Derivation via Method A (substrate) Derivation via Method B (soil profiles) effective field capacity (mm) – – – – – – – – Non-agricultural areas Natural regions Rivers loess lessivé loess pseudogley mountainous soils glacial sand sandy loess

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH mm Sensitivity analyses Total runoff

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Sensitivity analyses

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Conclusion Changing effective field capacity raised total runoff values by 5% The changes in annual precipitation caused a nearly 19% decrease and a 20% increase in total runoff values

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Calculation of N losses Nl = (N BAL – N DEN ) * EF Nl = Potential annual N load (kg N /ha) N BAL = Agricultural nitrogen balance (kg N/ha) N DEN = Denitrification (kg N/ha) EF = Exchange factor Ex = (GWR / FCrs) * 100 Ex = Exchange frequency of soil water (%) GWR= Groundwater recharge rate (mm) FCrs= Field capacity in rooted soil (mm)

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Sensitivity analyses Sensitive analysis 1 Sensitive analysis 2 7% reduction in mean annual precipitation values (error calculated by Wendland 1999) Sensitive analysis 3 Sensitive analysis 4 Increase in the agricultural nitrogen balance of 30 kg/ha*a, consideration of the atmospheric deposition, d erivation of effective field capacity acc. to Method A Sensitive analysis 5 Derivation of field capacity acc. to Method B (error calculated by Wendland 1999) 7% increase in mean annual precipitation values Increase in the agricultural nitrogen balance of 30 kg/ha*a, consideration of the atmospheric deposition, derivation of effective field capacity acc. to Method B

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Sensitivity analyses

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH gaseous deposition: e.g. NH 3, NO, NO 2, HNO 3 total N-deposition dry deposition wet deposition gaseous deposition soilvegetationbulk-deposition solid deposition Calculation of the total N deposition Mehlert 1996 Integral total nitrogen method (Weigel et al. 2001)

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Sensitivity analyses

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Langweiler einfügen Mg calculation reference Mg Sensitivity analyses 1986– –99

UFZ UMWELTFORSCHUNGSZENTRUM LEIPZIG-HALLE GmbH Conclusions Calculation of total runoff:  Changing effective field capacity causes a 5% change in the results, ann. precipitation approx. 20%. Calculation of N losses:  Changing soil and climate parameters change the results by up to 10%.  The main uncertainty: considering total atmogen deposition. - high uncertainty of the input data - high sensitivity for the results Further investigations of the total atmogen deposition in different crops and different natural regions are necessary to improve the uncertainties of the calculation of N losses.