SWAT Literature Database for Peer-Reviewed Journal Articles

Title:Daily nitrate losses: Implication on long-term river quality in an intensive agricultural catchment of south-western France 
Authors:Boithias, L., R. Srinivasan, S. Sauvage, F. Macary and J.M. Sanchez-Perez 
Journal:Journal of Environmental Quality 
Article ID: 
URL (non-DOI journals): 
Broad Application Category:hydrologic & pollutant 
Primary Application Category:calibration, sensitivity, and/or uncertainty analysis 
Secondary Application Category:nutrient cycling and transport 
Watershed Description:1,110 km^2 Save River in southwestern France 
Calibration Summary: 
Validation Summary: 
General Comments:This article is part of a JEQ special SWAT section. 
Abstract:High nitrate concentrations in streams have become a widespread problem throughout Europe in recent decades, damaging surface water and groundwater quality. The European Nitrate 27 Directive fixed a potability threshold of 50 mg L-1 for European rivers. The performance of the Soil and Water Assessment Tool (SWAT) model was assessed in the 1110-km² Save catchment in south-western France for predicting water discharge and nitrate loads and 30 concentrations at the catchment outlet, considering observed data set uncertainty. Simulated values were compared with both intensive and extensive measurement data sets. Daily discharge fitted observations (ENS=0.61, R²=0.7, and PBIAS=-22%). Nitrate simulation 33 (1998-2010) was within the observed range (PBIAS=10-21%, considering observed data set uncertainty). Annual nitrate load at the catchment outlet was correlated to the annual water yield at the outlet (R²=0.63). Simulated annual catchment nitrate exportation ranged from 21 36 to 49 kg ha-1 depending on annual hydrological conditions (averaging 36 kg ha-1). Exportation rates ranged from 3 to 8% of nitrogen inputs. 34% of the nitrate load was exported during floods, which represented 18% of the 1998-2010 period. Average daily nitrate concentration 39 at the outlet was 29 mg L-1 (1998-2010), ranging from 0 to 270 mg L-1. Nitrate concentration exceeded the European 50 mg L-1 potability threshold during 244 days between 1998 and 2010. A 20% reduction of nitrogen input reduced crop yield by between 5% and 9%, and 42 reduced by 62% the days when the 50 mg L-1 threshold was exceeded.