Using SWAT-LUD Model to Estimate the Influence of Water Exchange and Shallow Aquifer Denitrification on Water and Nitrate Flux

Xiaoling Sun (1, 2, 3) , Léonard Bernard-Jannin (4, 5, 1) , Youen Grusson (1, 6, 7) , Sabine Sauvage (1) , Jeffrey Arnold (8) , Raghavan Srinivasan (9) , José Sánchez Pérez (1)

1 LEFE - Laboratoire Ecologie Fonctionnelle et Environnement
2 School of Environmental Science and Engineering
3 State Key Laboratory of Water Resources and Hydropower Engineering Science
4 ISTO - Institut des Sciences de la Terre d'Orléans - UMR7327
5 Biogéosystèmes Continentaux - UMR7327
6 Chaire de Recherche EDS en Previsions et Actions Hydrologiques
7 Departement of Soil and Environment
8 USDA-ARS : Agricultural Research Service
9 Texas A&M University [College Station]

Numerous studies have pointed out the importance of groundwater and surface water interaction (SW–GW) in a river system. However; those functions have rarely been considered in large scale hydrological models. The SWAT-LUD model has been developed based on the Soil and Water Assessment Tool (SWAT) model; and it integrates a new type of subbasin; which is called subbasin-LU (SL); to represent the floodplain area. New modules representing SW–GW exchanges and shallow aquifer denitrification are developed in the SWAT-LUD model. In this study; the SWAT-LUD model was applied to the middle floodplain area of the Garonne catchment in France. The results showed that the SWAT-LUD model could represent the SW–GW exchange and shallow aquifer denitrification appropriately. An annual 44.1 × 10 7 m 3 of water flowed into the river from the study area; but the annual exchanged water volume was 6.4 × 10 7 m 3 ; which represented just 1% of the river discharge. A total of 384 tons of N-NO 3 − (0.023 t·ha −1) was consumed by denitrification in the floodplain shallow aquifer annually. The nitrate concentration (N-NO 3 −) decrease in the channel was 0.12 mg·L −1 ; but in the shallow aquifer it reached 11.40 mg·L −1 ; 8.05 mg·L −1 ; and 5.41 mg·L −1 in LU1; LU2; and LU3; respectively. Our study reveals that; in the Garonne floodplain; denitrification plays a significant role in the attenuation of nitrate associated with groundwater; but the impacts of denitrification on nitrate associated with river water is much less significant.

Keywords: SWAT-LUD model; water exchange; denitrification; floodplain aquifer; Garonne River

Domains: Sciences of the Universe [physics]; Continental interfaces, environment

Xiaoling Sun, Léonard Bernard-Jannin, Youen Grusson, Sabine Sauvage, Jeffrey Arnold, et al.. Using SWAT-LUD Model to Estimate the Influence of Water Exchange and Shallow Aquifer Denitrification on Water and Nitrate Flux. Water, 2018, 10 (4), 528 (19 p.). ⟨10.3390/w10040528⟩. ⟨insu-01832774⟩