Modelling of agricultural diffuse pollution and mitigation measures

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
4. Modelling of further measures
request for news tools able to evaluate impact of measures token in
order to reduce pressures on ecosystems.
New European directives in the environmental field
(Nitrate Directive, Water Framework Directive, …)
In Wallonia …
In Wallonia …
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.
REFERENCE
- Use of a “soil and vadose” hydrological model : the EPICgrid model
“Walloon action plan for nitrogen sustainable management in
agriculture”
(PGDA1 (2002) and PGDA2 (2007))
- APL control
2. EPICgrid model
Precipitations
EPICGRID
Catchment
Modelisation
Soils and vadose zone
GRID SQUARE : 1 sq. km.
DEM
Climate data
Précipitationsannuelles(mm/an)
Moselle
Oise
D
1000
800
A
600
B
2004
2005
2000
2001
2002
2003
1995
1996
1997
1998
1999
1990
1991
1992
1993
1994
1986
1987
1988
1989
1981
1982
1983
1984
1985
1977
1978
1979
1980
1972
1973
1974
1975
1976
1971
Source : IRM et SETHY
Landuse, crop growth,
agricultural practices
C
B
Soils
Geology
In each grid square
ponderation
of the different components
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).
SCENARIOS
Direct Runoff
Infiltration
River
hydrographique en Région wallonne
Meuse
Escaut
1200
400
Transpiration
Evaporation
1600
1400
Snow
Deep
Percolation
2/3 cereals scenario
- 30 kg Nmin scenario
Deep recharge
Groundwater
Percolation
3. Modelling of the EU Nitrates Directive Actions Program
Effect of agricultural practices scenarios on nitrate
concentration of leaching water
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
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.
0%
Variation de la concentration en nitrate (mg NO3/l)
2016
Nitrate concentrations in leaching
waters under the root zone
Nitrate concentrations in leaching
waters under the root zone
Decrease of nitrate
concentrations
(effect of action's
program that
induces a
modification of
agricultural
practices)
European Geosciences Union
General Assembly 2012
Vienna, Austria, 22-27 April 2012
2018
2020
2022
2024
2026
-20%
-40%
-60%
-80%
-100%
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"
-120%
Nitrate concentrations in leaching
waters under the root zone
PROSPECTIVE
SIMULATIONS
1994 – 1999
Pasture scenario
Hypodermic
Groundwater
CLIMATE
UNCERTAINTIES
5. APL control
2016 - 2027
Nitrate concentrations in leaching
waters under the root zone
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.
2004 - 2009
Stabilisation of
nitrate
concentrations
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).
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 350359.