Bosherston Lakes in west Wales are an internationally important set of linked freshwater lowland ... more Bosherston Lakes in west Wales are an internationally important set of linked freshwater lowland lakes which were created by damming tidal creeks in the 18th and 19th centuries. The lakes have an average water depth of 1–3 m, and receive surface water inflows but have an uncertain interaction with the underlying karstic Carboniferous Limestone. This paper describes the application of the Soil Water Assessment Tool (SWAT) to improve the understanding of the hydrological functioning of the lake system. The temporally variable and limited observational data were used within a two-step calibration process. The simulated surface water inflows and groundwater levels were calibrated, followed by the lake volumes (Nash–Sutcliffe (NS) coefficient ranging from 0.67 to 0.74). Finally the simulated lake volumes were validated (NS ranging from 0.56 to 0.74) and the simulated lake outflows demonstrated to be plausible. Simulations reveal that three of the four linked water bodies lose significant water to the underlying aquifer. The simulated water balance demonstrates that the catchment outputs are dominated by evapotranspiration, surface outflow from the lake system to the sea and coastal groundwater discharge, with abstraction and lake evaporation being of lesser importance. The coastal groundwater discharge originates from both leakage from the lakes and previously unrecognised larger scale groundwater flow paths in the limestone aquifer. The study has provided an improved basis for the future hydrological management of the catchment and lakes and has demonstrated the wider utility of SWAT in simulating karstic systems.
The study analyzes the source apportionment of a river basin, the Dese-Zero river, located within... more The study analyzes the source apportionment of a river basin, the Dese-Zero river, located within the North-Eastern part of the Venice Lagoon Watershed (VLW), Italy. The Dese-Zero river basin is characterised by a very intensive agriculture and landfarming system. To assess the source apportionment, two different models have been applied: the QUAL2E model for the simulation of the dry weather scenario and the BASINS-SWAT model for the simulation of the wet weather scenario. Out of a total nitrogen load of 512 t N y −1 , for a surface of 293 km 2 , in dry weather conditions the apportionment was found as follows: 20% point sources (i.e. WWTP and industrial discharge and direct sewer discharge into surface waters) and about 80% attributed to not rain-driven diffuse loads (i.e. groundwater/spring recharge and tributary/irrigation channels coming from bordering watersheds). As far as rainy events are concerned, the surface runoff load was of about 200 t N y −1 , over a total annual nitrogen load of about 700 t N y −1 . Therefore, on an annual basis, the total source apportionment was found as follows: about 30% surface runoff loads, about 15% point sources and about 55% of the total annual load was found to be constituted by not rain-driven diffuse sources.
The study analyzes the source apportionment of a river basin, the Dese-Zero river, located within... more The study analyzes the source apportionment of a river basin, the Dese-Zero river, located within the North-Eastern part of the Venice Lagoon Watershed (VLW), Italy. The Dese-Zero river basin is characterised by a very intensive agriculture and landfarming system. To assess the source apportionment, two different models have been applied: the QUAL2E model for the simulation of the dry weather scenario and the BASINS-SWAT model for the simulation of the wet weather scenario. Out of a total nitrogen load of 512 t N y −1 , for a surface of 293 km 2 , in dry weather conditions the apportionment was found as follows: 20% point sources (i.e. WWTP and industrial discharge and direct sewer discharge into surface waters) and about 80% attributed to not rain-driven diffuse loads (i.e. groundwater/spring recharge and tributary/irrigation channels coming from bordering watersheds). As far as rainy events are concerned, the surface runoff load was of about 200 t N y −1 , over a total annual nitrogen load of about 700 t N y −1 . Therefore, on an annual basis, the total source apportionment was found as follows: about 30% surface runoff loads, about 15% point sources and about 55% of the total annual load was found to be constituted by not rain-driven diffuse sources.
Bosherston Lakes in west Wales are an internationally important set of linked freshwater lowland ... more Bosherston Lakes in west Wales are an internationally important set of linked freshwater lowland lakes which were created by damming tidal creeks in the 18th and 19th centuries. The lakes have an average water depth of 1–3 m, and receive surface water inflows but have an uncertain interaction with the underlying karstic Carboniferous Limestone. This paper describes the application of the Soil Water Assessment Tool (SWAT) to improve the understanding of the hydrological functioning of the lake system. The temporally variable and limited observational data were used within a two-step calibration process. The simulated surface water inflows and groundwater levels were calibrated, followed by the lake volumes (Nash–Sutcliffe (NS) coefficient ranging from 0.67 to 0.74). Finally the simulated lake volumes were validated (NS ranging from 0.56 to 0.74) and the simulated lake outflows demonstrated to be plausible. Simulations reveal that three of the four linked water bodies lose significant water to the underlying aquifer. The simulated water balance demonstrates that the catchment outputs are dominated by evapotranspiration, surface outflow from the lake system to the sea and coastal groundwater discharge, with abstraction and lake evaporation being of lesser importance. The coastal groundwater discharge originates from both leakage from the lakes and previously unrecognised larger scale groundwater flow paths in the limestone aquifer. The study has provided an improved basis for the future hydrological management of the catchment and lakes and has demonstrated the wider utility of SWAT in simulating karstic systems.
The study analyzes the source apportionment of a river basin, the Dese-Zero river, located within... more The study analyzes the source apportionment of a river basin, the Dese-Zero river, located within the North-Eastern part of the Venice Lagoon Watershed (VLW), Italy. The Dese-Zero river basin is characterised by a very intensive agriculture and landfarming system. To assess the source apportionment, two different models have been applied: the QUAL2E model for the simulation of the dry weather scenario and the BASINS-SWAT model for the simulation of the wet weather scenario. Out of a total nitrogen load of 512 t N y −1 , for a surface of 293 km 2 , in dry weather conditions the apportionment was found as follows: 20% point sources (i.e. WWTP and industrial discharge and direct sewer discharge into surface waters) and about 80% attributed to not rain-driven diffuse loads (i.e. groundwater/spring recharge and tributary/irrigation channels coming from bordering watersheds). As far as rainy events are concerned, the surface runoff load was of about 200 t N y −1 , over a total annual nitrogen load of about 700 t N y −1 . Therefore, on an annual basis, the total source apportionment was found as follows: about 30% surface runoff loads, about 15% point sources and about 55% of the total annual load was found to be constituted by not rain-driven diffuse sources.
The study analyzes the source apportionment of a river basin, the Dese-Zero river, located within... more The study analyzes the source apportionment of a river basin, the Dese-Zero river, located within the North-Eastern part of the Venice Lagoon Watershed (VLW), Italy. The Dese-Zero river basin is characterised by a very intensive agriculture and landfarming system. To assess the source apportionment, two different models have been applied: the QUAL2E model for the simulation of the dry weather scenario and the BASINS-SWAT model for the simulation of the wet weather scenario. Out of a total nitrogen load of 512 t N y −1 , for a surface of 293 km 2 , in dry weather conditions the apportionment was found as follows: 20% point sources (i.e. WWTP and industrial discharge and direct sewer discharge into surface waters) and about 80% attributed to not rain-driven diffuse loads (i.e. groundwater/spring recharge and tributary/irrigation channels coming from bordering watersheds). As far as rainy events are concerned, the surface runoff load was of about 200 t N y −1 , over a total annual nitrogen load of about 700 t N y −1 . Therefore, on an annual basis, the total source apportionment was found as follows: about 30% surface runoff loads, about 15% point sources and about 55% of the total annual load was found to be constituted by not rain-driven diffuse sources.
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