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

Abstract

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.

The Functioning of a Water Body Within a Fluvio-Lacustrine System as an Effect of Excessive Nitrogen Loading—The Case of Lake Symsar and its Drainage Area (Northeastern Poland)

“…Depending on the prevailing conditions, numerous processes occur in water which affect the transformation of nitrogen and its deposition on the bottom. The main processes of nitrogen transformation in surface waters include nitrification and denitrification processes [7]. Anaerobic bacteria are involved in denitrification by producing a gas in the form of nitrogen oxide or nitrogen dioxide by converting nitrate nitrogen into nitrite nitrogen.…”

Daily denitrification rates in floodplains under contrasting pedo-climatic and anthropogenic contexts: modelling at the watershed scale

“…While POC mostly comes from soil erosion, DOC is a result of soil leaching (Meybeck, 1993;Raymond and Bauer, 2001). DOC is the most consumed OC form in denitrification (Peyrard et al, 2011;Zarnetske et al, 2011;Sun et al, 2018).…”

“…Modelling tools that focus on the exchanges between rivers and floodplains were usually used for hydrology interactions (Yamazaki et al, 2011;Jung et al, 2012). Regarding floodplains biogeochemistry, previous models showed their ability to simulate denitrification (Hattermann et al, 2006;Sun et al, 2018). They can be used to identify nitrate sources and sinks (Boano et al, 2010;Peyrard et al, 2011;Zarnetske et al, 2012) as well as hot spots and hot moments of nutrients cycling (Groffman et al, 2009;Bernard-Jannin et al, 2017).…”

“…They can be used to identify nitrate sources and sinks (Boano et al, 2010;Peyrard et al, 2011;Zarnetske et al, 2012) as well as hot spots and hot moments of nutrients cycling (Groffman et al, 2009;Bernard-Jannin et al, 2017). Two options are commonly used to estimate denitrification at large scale: coupling a hydrological with biogeochemical models (Peyrard et al, 2011) or implementing biogeochemical modules in a hydrological model (Sun et al, 2018). Sun et al (2018) was the first study to show models capacity to simulate daily denitrification variations at the scale of a reach by considering the river-aquifers exchanges of water, nitrate and OC.…”

“…Two options are commonly used to estimate denitrification at large scale: coupling a hydrological with biogeochemical models (Peyrard et al, 2011) or implementing biogeochemical modules in a hydrological model (Sun et al, 2018). Sun et al (2018) was the first study to show models capacity to simulate daily denitrification variations at the scale of a reach by considering the river-aquifers exchanges of water, nitrate and OC. Denitrification is usually modelled as a nitrate retention rate (Boyer et al, 2006;Ruelland et al, 2007;Peyrard et al, 2011;Sun et al, 2018).…”