Nitrate retention at the river–watershed interface: a new conceptual modeling approach

Gilles Billen (1) , Antsiva Ramarson (1) , Vincent Thieu (1) , Sylvain Théry (1) , Marie Silvestre (1) , Catherine Pasquier (2) , Catherine Hénault (2) , Josette Garnier (1)

1 METIS - Milieux Environnementaux, Transferts et Interactions dans les hydrosystèmes et les Sols
2 URSols - Unité de Science du Sol (Orléans)

Denitrification in riparian wetlands plays a major role in eliminating nitrate coming from agricultural watershed uplands before they reach river water. A new approach was developed for representing this process in the biogeochemical Riverstrahler model, using a single adjustable parameter representing the potential denitrification rate of wetland soils. Applied to the case of three watersheds with contrasting size, land-use and hydro-climatic regime, namely the Seine and the Loir rivers (France) and the Red River (Vietnam), this new model is able to capture the general level of nitrate concentrations as well as their seasonal variations everywhere over the drainage network. The nitrogen budgets calculated from the results show that riparian denitrification eliminates between 10 and 50% of the diffuse sources of nitrogen into the hydrosystem coming from soil nitrate leaching.

Mots clés: river systems; riparian retention; soil denitrification; nitrate

Domaines: Géochimie

Gilles Billen, Antsiva Ramarson, Vincent Thieu, Sylvain Théry, Marie Silvestre, et al.. Nitrate retention at the river–watershed interface: a new conceptual modeling approach. Biogeochemistry, 2018, 139 (1), pp.31-51. ⟨10.1007/s10533-018-0455-9⟩. ⟨hal-01822912⟩