Best Management Practices for surface water resources in the Paris metropolitan area :prevention of non point pollution by nitrates and pesticides

摘要

The nitrates contamination in the three main rivers of the Paris area (Seine, Marne and Oise) is not yeta major issue. The nitrate content generally stay below the maximum acceptable concentration level(50 mg/l). However, the contamination is increasing, with concentrations in winter about 25-35 mg/l,and peaks which can briefly reach the maximum acceptable concentration level during winter floods. In2010, the risk of exceeding the threshold will be about 10 days per year. These observations weremade by the Syndicat des Eaux d'Ile-de-France (SEDIF), a large association of municipalities whichsupply drinking water to 4 million inhabitants in the Parisian suburbs. The SEDIF is currently involved ina large scale programme to prevent nitrate pollution which takes place in the Marne river basin.The prevention programme is built on a strong partnership between several drinking water producersand organisations involved in agricultural development. The programme, which began in 1997, istaking place in a 2000 km2 intensive cereal growing area in the Department of Seine-et-Marne. Theprogramme concerns approximately 1000 farmers. The two main purposes of the programme are onone hand the adjustment of the fertilisation practices, and on the other hand the plot management inwinter. It is during winter, when the hydrologic balance is positive, that nitrates are exported towardsthe surface water and the aquifer.In order to evaluate the programme, indicators have been set up to monitor the various tasks which areimplemented, the impact of the advice on the farmers, or the land use development related to nitraterisks. After four years of work, the structures of the programme have now been clearly identified andaccepted by stakeholders. The partners now have to take the project further by implementing newactions to prevent the pollution of pesticides.