Citation:
M. Vale, I.P. Holman, Understanding the hydrological functioning of a shallow
lake system within a coastal karstic aquifer in Wales, UK, Journal of Hydrology,
Volume 376, Issues 1-2, 30 September 2009, Pages 285-294
Abstract:
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 syst