Deux-Sevres County: fighting water nitrate pollution using satellite-derived information
The County Directorate for Territories
Deux-Sèvres is a county in the Poitou-Charentes French region. Its economy is mainly based on the rural sector which provides jobs for a large part of the local population.
The County Directorate for Territories is the authority in charge of ensuring the sustainable use of the land, classified as a Nitrate Vulnerable Zone because of its intensive agriculture activities.
Used as fertilizers, nitrates are a major source of water pollution. The Nitrates Directive makes it mandatory for farmers to grow catch crops between farming seasons, to prevent nitrates from permeating into the ground with the rain, then into fresh water.
To control crops are actually grown, the Directorate needs to send inspectors to the fields. However, there are too few inspectors available for the size of the land, so only a limited part is really done. To comply with the 4th Action Programme, setting measures from the Directive for 2009-2012, the Directorate needed a complete overview of the land by the end of 2012, so as to focus field controls on the most exposed areas.
“(…) it is therefore necessary (…) to reduce water pollution caused or induced by nitrates from agricultural sources and to prevent further such pollution” Nitrates Directive 91/676/EEC
The satellite solution
The Directorate started using satellite-derived maps to detect whether parcels are covered with catch crops, in cooperation with the Earth Observation and Geoinformation for Land and Environment laboratory (TETIS) of the National Research Institute of Science and Technology for Environment and Agriculture (IRSTEA), and GEOSUD (GeoInformation for Sustainable Development) – a French database of satellite data, free for public authorities.
These data enable to better spot the areas with no cover and to prioritise site inspections. Four methods have been tested, and the last one, based on a risk assessment approach and taking into account various parameters such as crop types, seems to be very efficient and promising.
Thanks to satellite information, the Directorate is able, for the first time in France, to build priority maps focusing on areas most affected by nitrates pollution risk, thus optimising field inspections and saving time. Obtaining free data has helped keep costs down. The approach makes it easier for the county to comply with requirements of the Directive, and prepares it for the 5th Action Programme to be enforced in 2014.
“Satellite imagery is a real asset to fight against nitrate pollution.” Nicolas Cornuault, Deux-Sèvres County