wAbstract
@In order to model the nitrate concentration of the recharge water
in a spatially distributed way for the agricultural areas of the
Walloon Region of Belgium, the EPIC model was first adapted to
the specific soil description by modifying the reservoir sizes.
It was also adapted to the regional crop production by modifying
classcrop files in relation with observed data (both aerial and
underground crop growth, yield) in wheat, sugar beet, and potato
fields. As the vadose zone presents a depth between 1.5 and 104
m in this region, new reservoirs were added according to the geological
descriptions available. Deep nitrate transfer was validated in
a specific site where cropping history was known. Nitrate nitrogen
after harvest in the root zone was validated for wheat within
different crop rotations using the first results of a nitrate-monitoring
program planned by the authorities to test the effectiveness of
the mitigation measures in agriculture.
@This extended model was also linked to a GIS (geographical information
system) using 1 km2-cells. All the required were rasterised
to allow HRU (hydrological response unit) identification within
the cells. The cell's daily water flows are weighted flows of
each HRU depending on their relative area within the cell. Water
balances at catchment scale allow us to validate the calculation.
@Taking into account the evolution of distributed land use and
observed climatic data, we have built maps of fast indicators
and long-term indicators. The first map represents nitrate concentration
in the water leaving the root zone and the second one represents
the time transfer for nitrate from 1.5 m depth to the groundwater
table and nitrate concentration in recharge water. These maps
constitute major tools for nitrogen management at a regional level.
Keywords: EPIC model; GIS; Nitrate; Walloon Region; Nitrate diffuse
pollutionx
Introduction
Materials and methods
Results
@Deep 1D modelling and validation
@Distributed modelling and validation
@Nitrate management maps
Discussion and conclusions
Acknowledgements
References