Hydrogeology and hydrogeochemistry of a small, hard-rock island — the heavily stressed aquifer of Jersey

Abstract

The fractured basement aquifer of Jersey provides 30% of the total water needs of the island plus baseflow to surface catchment storage. A 3-year field study has attempted to describe the groundwater resources in terms of quantity and quality. Borehole yields are typically less than 11s −1; the island-wide estimate of transmissivity is 3 m 3 day −1 and effective aquifer thickness is 30–40 m although deeper circulation occurs in selected fracture systems. It is estimated that much of the renewable resource is exploited. Groundwaters are predominantly derived from recent recharge, most being oxidising with measurable tritium contents. There is widespread pollution from agricultural nutrients but natural denitrification is apparent in some areas.