Abstract :
[en] In Europe, 30% of groundwater bodies are considered to be at risk of not achieving the
Water Framework Directive (WFD) ‘good status’ objective by 2015, and 45% are in doubt of
doing so. Diffuse agricultural pollution is one of the main pressures affecting groundwater
bodies. To tackle this problem, the WFD requires Member States to design and implement
cost-effective programs of measures to achieve the ‘good status’ objective by 2027 at the
latest. Hitherto, action plans have mainly consisted of promoting the adoption of Agri-
Environmental Schemes (AES). This raises a number of questions concerning the
effectiveness of such schemes for improving groundwater status, and the economic
implications of their implementation. We propose a hydro-economic model that combines a
hydrogeological model to simulate groundwater quality evolution with agronomic and
economic components to assess the expected costs, effectiveness, and benefits of AES
implementation. This hydro-economic model can be used to identify cost-effective AES
combinations at groundwater-body scale and to show the benefits to be expected from the
resulting improvement in groundwater quality. The model is applied here to a rural area
encompassing the Hesbaye aquifer, a large chalk aquifer which supplies about 230,000
inhabitants in the city of Liege (Belgium) and is severely contaminated by agricultural
nitrates. We show that the time frame within which improvements in the Hesbaye
groundwater quality can be expected may be much longer than that required by the WFD.
Current WFD programs based on AES may be inappropriate for achieving the ‘good status’
objective in the most productive agricultural areas, in particular because these schemes are
insufficiently attractive. Achieving ‘good status’ by 2027 would demand a substantial change
in the design of AES, involving costs that may not be offset by benefits in the case of chalk
aquifers with long renewal times.
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