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Institute of Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, Oxfordshire OX10 8BB, UK
There has been growing concern that groundwater abstraction on the island of Jersey may exceed recharge, with the consequent depletion of the island’s finite water resources. A three-year study to determine groundwater recharge through hydrological modelling is nearing completion. A daily model has been developed which predicts evapotranspiration, soil moisture, recharge and streamflow from inputs of rainfall and potential evapotranspiration. Preliminary calibration of the model has used data collected from a small, intensively instrumented catchment around Trinity, Jersey, between April 1993 and December 1994. Subsequent validation, for the pre-study period January 1990 to December 1992, has shown estimated net recharge for the catchment as a whole to be 50 mm, with an initial depletion of groundwater reserves in 1990 followed by two years of positive recharge. Net recharge under a grass site was estimated to be slightly more than under arable land. Model calibration and validation will be reworked following collation of the 1995/96 dataset. The model will then be run on 25 years of catchment rainfall and potential evapotranspiration data to estimate recharge patterns over the period 1968–92, and to assess the impact of different abstraction rates.
