Modelling of agricultural diffuse pollution and mitigation measures

In parallel to this modelling, the respect of the PGDA application by farmers is evaluated each
year by a measuring campaign of the autumn nitrogen content in the soil profile. The
confrontation of these measurements with the model results allows us to improve the
representativeness of the EPICgrid model in areas in witch agricultural practices can’t be
correctly defined on the basis of regional statistics.
“Walloon action plan for nitrogen sustainable management in
agriculture”
(PGDA1 (2002) and PGDA2 (2007))
New European directives in the environmental field
(Nitrate Directive, Water Framework Directive, …)
Modelling of agricultural diffuse pollution and mitigation measures
effectiveness on water quality in Wallonia (Southern Region of Belgium)
Sohier C. & Degré A.
University of Liege (Belgium)
Gembloux Agro-Bio Tech
Soil – Water Systems
1. Context
2. EPICgrid model
3. Modelling of the EU Nitrates Directive Actions Program
The EPICgrid model has been developed at
catchment scale with an original modular concept
on the basis of the field scale “water-soil-plant”
EPIC model (Williams et al., 1984). The model
calculates for each calculation unit identified into a
grid of 1 square kilometer water and nutrients
flows into the plant-soil-vadose zone system
(Sohier et al., 2009).
4. Modelling of further measures
Percolation
B
A
C
B
D
A
C
BA
C
BA
C
BA
C
B
D
GeologyGeology
In each grid square
ponderation
of the different components
DEMDEM
B
D
A
C
BA
C
B
D
SoilsSoils
GRID SQUARE : 1 sq. km .
Landuse, crop growth,
agricultural practices
Landuse, crop growth,
agricultural practices
Landuse, crop growth,
agricultural practices
EPICGRID
Catchment
Modelisation
Soils and vadose zone
hydrographique
en
Région
wallonne
400
600
800
1000
1200
1400
1600
1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005
Précipit at io ns annuell es (mm/an)
Meuse
Escaut
Moselle
Oise
Source : IRM et SETHY
Climate data
5. APL control
Acknowledgements
The model’s development was carried out with the financial support of the Walloon Region and
the public society of water management (Société Publique de Gestion de l’Eau).
European Geosciences Union
General Assembly 2012
Vienna, Austria, 22-27 April 2012
References :
Williams J.R., Jones C.A., Dyke P.T. (1984). A modelling approach to determining the relationship between erosion and soil productivity. Transactions of the ASAE. 27, 129-144
Sohier C., Degré A., Dautrebande S. (2009). From root zone modelling to regional forecasting of nitrate concentration in recharge flows – The case of the Walloon Region (Belgium). Journal of Hydrology, Volume 369, Issues 3-4, 15 May 2009, Pages 350-
359.
request for news tools able to evaluate impact of measures token in
order to reduce pressures on ecosystems.
In Wallonia …
- Use of a “soil and vadose” hydrological model : the EPICgrid model
- APL control
Precipitations
Deep recharge
Evaporation
Snow Transpiration
Direct Runoff
Infiltration
River
Groundwater
Hypodermic
Groundwater
Deep
Percolation
The model was used to make actual and prospective simulations in order to evaluate the impact, at regional scale, of measures currently performed to reduce the
effect of diffuse pollution on water surface quality and groundwater quality. Response of the soil-vadose zone to agricultural practices modification is analyzed for
the deadlines of the Water Framework Directive : 2015, 2021 and 2027, for two climatic scenarios. Simulations results showed that actual measures are not
sufficient in some areas and that new actions are necessary.
The EPICgrid model was then used to evaluate effectiveness of further measures that can be
implemented in order to reduce agricultural diffuse pollution. The increasing of catch crops
from 75% to 100% in vulnerable zones has showed a limited impact. The modifications of
agricultural practices such as crop rotations or mineral fertilizing amounts have showed a more
significant impact on water quality.
Decrease of nitrate
concentrations
(effect of action's
program that
induces a
modification of
agricultural
practices)
Stabilisation of
nitrate
concentrations
Modèle EPICgrid - Impact par rapport au scénario de référence (*) de scénarios de
pratiques agricoles sur la concentration en nitrate des eaux de lessivage à la base de
la zone racinaire - Zone de prévention des captages de Hesbaye
-120%
-100%
-80%
-60%
-40%
-20%
0%
2016 2018 2020 2022 2024 2026
Variation de la concentration en nitrate (mg NO3/l)
Scénario "2/3 céréales" - Scénario climatique "High"
Scénario "2/3 céréales" - Scénario climatique "Low"
Scénario "2/3 céréales" - Moyenne 2016-2027
Scénario "-30 kg Nmin " - Scénario climatique "High"
Scénario "-30 kg Nmin " - Scénario climatique "Low"
Scénario "-30 kg Nmin " - Moyenne 2016-2027
Scénario "Prairie de fauche" - Scénario climatique "High"
Scénario "Prairie de fauche" - Scénario climatique "Low"
Scénario "Prairie de fauche" - Moyenne 2016-2027 (*) Scénario de référence : Pratiques
agricoles "Zone de préventon - 2010"
In Wallonia …
PROSPECTIVE
SIMULATIONS CLIMATE
UNCERTAINTIES
Nitrate concentrations in leaching
waters under the root zone Nitrate concentrations in leaching
waters under the root zone
Nitrate concentrations in leaching
waters under the root zone
Nitrate concentrations in leaching
waters under the root zone
1994 – 1999 2004 - 2009
2016 - 2027
REFERENCE
2/3 cereals scenario - 30 kg Nmin scenario Pasture scenario
SCENARIOS
Effect of agricultural practices scenarios on nitrate
concentration of leaching water