Teledetection to Protect Water Catchment
Bosc, Christelle1; Araqi, Al Bachir2; Guinet, Jonathan3; Savinaud, Mickael3; Rucquoi, Sébastien1; Ruiloba, Rosa3
1CETE Sud-Ouest, FRANCE; 2Student, FRANCE; 3C-S, FRANCE

In response to demands from the european framework directive on water, the Water and aquatic environments law of 30 December 2006 has strengthened the existing control against diffuse pollution from agriculture by creating "zones of water catchment protection", on which will be implemented in a program of action. This program aims at changing agricultural practices upstream of the abstraction of drinking water to reduce discharges of nitrates and pesticides and to improve the quality of the resource. Delineation of catchments feeding occurs following methodologies in order to identify area that may affect the quality of water produced. These methodologies are based on both geological and hydrological elements but also on surface elements (detection of index such as points of natural or artificial absorption- type sinkholes, wells, ..., agricultural drainage systems, gaps, cracks, clogging rivers ...). These items are currently observed [ref rapport BRGM] on the basis of in situ visits, aerial photography and data mainly costly, and whose characteristics are not necessarily the most appropriate. South West CETE worked close to end-users in charge of identifying those protected areas in order to understand their needs. The identification of regional area whitout information is another objective. Those needs will be presented. Moroverd a study showing the benefits of using satellite images to detect drainage elements have been conduced. Several drainage elements have been detected in this preliminary study. Sinkholes and hydrological network can be mapped thanks to an automatic analysis of DEM data, natural drains and satellite images. Benefits of using satellite data will be detailed for each of those elements. This methodology developped with C-S is based on the use of free and open source solutions like Quantum GIS, GRASS GIS softwares and Orfeo ToolBox for raster analysis.