The catchment is comprised of two major aquifers: the Brighton Chalk Block of the South Downs, and the thin ridge of Lower Greensand which outcrops to the north of the Downs and runs parallel to the chalk escarpment.

The Brighton Chalk Block is by far the largest aquifer underlying the catchment. It is a crucial water source for public water supply for Lewes, Brighton and Hove, and neighbouring towns on the south coast as well as many rural communities. Groundwater is therefore a fundamental ecosystem service, provided by the catchment to the catchment, whether it be from the scarp slope springs at Poynings and Fulking or groundwater fed brooks at Lewes and Offham.

Scarp slopes at Fulking

Design by LTD Design Consultants and build by Garganey Consulting. From an original concept by the Herts and Middlesex Wildlife Trust.