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Entec (UK) Ltd, 160–162 Abbey Foregate, Shrewsbury, Shropshire SY2 6AL, UK
Redgrave and Lopham Fens lie at the headwaters of the Rivers Waveney and Little Ouse in East Anglia, UK. The Fens are supported by groundwater discharge from the drift-covered Chalk underlying the area. This discharge and the ecological value of the Fens have been derogated by public water supply abstractions from a nearby borehole.
Aspects of the investigations undertaken to construct a groundwater model to assess options for relocating the borehole away from the Fens are described. Particular attention is given to the value of using basic river flow data analysis to identify contrasts in the hydrological characteristics of the two catchments and constrain estimates of recharge.
The Waveney catchment is flashy and dominated by run-off whereas the Little Ouse receives a more significant groundwater baseflow contribution. These catchment contrasts reflect subtle variations in boulder clay thicknesses and topography. They also reflect the contrasting effectiveness of the two rivers as drains on the groundwater system.
Average recharge to the Chalk through the boulder clay-covered interfluves is estimated at around 36 mm a–1 (which is similar to other values quoted in the literature). Recharge may locally fall to less than 10 mm a–1 where the boulder clay is thick and the Chalk is strongly confined.
