Concentration and nitrogen flux of the Brittany watersheds.

A spatial layer of Breton watersheds is integrated with a dynamic graph visualisation tool on the evolution of water quality in nitrate. The spatial information layer relating to the contours of Breton watersheds is produced by processing the Digital Terrain Model using the MNTSurf software developed by Agrocampus Ouest — UMR SAS. Most of the outlets in these watersheds correspond to so-called “at sea” outlets that are positioned either at dams or obstacles that materialise the boundary between fresh and salted marine waters, or at the point of intersection between the linear of the water body “stream” and the “transition” or “shore” water bodies (source BD Carthage — water bodies defined under the WFD). Inland, the outfalls of sub-watersheds generally correspond to confluence points of the hydrographic network. Each of these basins or sub-watersheds has a reference water quality monitoring station (called Quality Station) as close as possible to the outlet. A large part of these basins are also equipped with a limnimetric station called Debit Station. For each watershed with chronic nitrate concentration and flow data, nitrogen concentration and flow graphs are generated automatically using a software called “Macroflux”. The graphical representations relate to the following indicators: hydraulicity, daily concentration, annual average concentration, annual flows, average specific flow, hydraulicity-weighted flux. The attribute table of the spatial layer contains a “Macroflux” field that points, for each watershed, to a web application offering the above dynamic graphs. Example of a graph for the Elorn basin: http://geowww.agrocampus-ouest.fr/cseb/dygraph_upsize.php?g=6&Varbv_id=61&VarBV=ELORN This work is the result of a study launched by the Conseil scientifique de l’environnement de Bretagne (CSEB) in 2008 in connection with the Regional Council and the DREAL Bretagne. This layer of information is integrated into a cartographic web portal developed by UMR SAS Agrocampus Ouest-INRA. To access this portal: https://geosas.fr/portails/?portail=cseb For more information on the data and calculations, see the explanatory leaflet: https://geosas.fr/metadata/pdf/notice_portailweb_cseb.pdf To master the graph viewer, consult the video tutorial: https://www.youtube.com/watch?v=7i-qM6NI6K8