Programme  OS1n Water quality 2  abstract 639

Evaluation of strategies to reduce nitrate pollution of groundwater

Author(s): assessing the needs and efficiencies of agri-environmental measures for selected groundwater bodies in Germany
Author(s): Ralf Kunkel, Michael Eisele, Frank Wendland
Ralf Kunkel, Research Centre Juelich, Institute for Chemistry and Dynamics of the Geosphere, Wilhelm-Johnen-Str., 52425 Jülich, Germany, Phone: ++49 (0) 2461 61 3262, Fax: ++49 (0) 2461 61 2518, E-mail:

Keyword(s): Diffuse nitrate pollution, river basin management, EU - Water Framework Directive, multicriteria assessment, nitrogen reduction measures

Article: abs639_article.pdf
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Session: OS1n Water quality 2
The implementation schedule for the EU water framework directive requires the

establishment of river basin district management programmes until 2009. In Germany, the reduction of nitrogen load

into groundwater, mostly caused by diffuse emission from agriculture, is one of the most challenging tasks. Within the

EU-Life project WAgriCo (Water Resources Management in Cooperation with Agriculture) nitrogen management

options adapted to hydrological and agro-economic site properties are developed and implemented for three pilot

areas in the Federal State of Lower Saxony using new participation approaches and technologies suitable for

programmes of measures to reduce diffuse pollution from agriculture.
The definition of environmental

objectives is an indispensable precondition for assessing the required amount and efficiency of water protection

measures. In the WAgriCo-project a nitrate concentration in percolation water of 50 mg/l has been defined as the

environmental target for groundwater protection. This value, however, is regarded as an average for a larger area

defined by the groundwater bodies and their hydrogeological subdivisions rather than as for each individual site. For

each of these subdivisions, the current pressure of agriculture to groundwater is quantified. For the evaluation of the

amount and efficiency of certain water protection measures, the required reduction of N-surpluses to accomplish the

environmental target needs to be quantified, using the current status as a reference.
A integrative

macroscale agroeconomic-hydrogeological model is used to simulate the interactions between agricultural practice,

nitrogen surpluses and the nitrogen flow through the soil and aquifer to the outflow into surface waters. The actual

nitrate concentrations in percolation water are calculated for the entire Federal State of Lower Saxony on a 50 x 50

m resolution considering site-characteristics, N-surpluses, water balance and denitrification in the soil. The tolerable

N-surpluses needed to meet the environmental target are quantified as averages for each of the hydrogeological

subdivisions by “inverse” calculation using this model system. The required reduction of N-surpluses can then be

estimated by comparing the tolerable N-surpluses to the actual state of nitrogen emission.

the WAgriCo project a number of measures and measure combinations with detailed management prescriptions

were selected and evaluated with regard to its potential N-surplus. By using the nitrogen export model their effects

are assessed with respect to the nitrate leaching to groundwater and surface waters. The measures effectivenesses

and its needs are evaluated area-differentiated for each of the areas considered.

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