Hydrology of eastern Mendip showing stream sinks, springs and tracer test flow paths. The largest springs are named.

By placing the dye in a stream sink and seeing where, and how long it takes until the dye reappears at one or more springs, coupled with direct exploration by cavers and cave divers, the underground drainage pattern of the region can be deduced. Over the past forty years, numerous tracer tests have been carried out by cavers, university academics and water companies in an effort to understand the underground drainage pattern.

The underground streamway in Stoke Lane Slocker.
A stream sink, Stoke Lane Slocker, Stoke St Michael.

St Dunstans Well, Stoke St Michael.

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