Wimbleball Reservoir licensed pumped storage abstraction

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Wimbleball Lake, on the edge of Exmoor is managed for both recreational purposes and as a reservoir by Wessex water, and along with Clatworthy Reservoir supplies much of the Taunton Deane area.  The lake is fed by the upper reaches of the River Haddeo and a second small stream, whilst downstream of the dam compensation flows are periodically released into the river in order to maintain a healthy flow regime throughout the year and support its substantial salmonid fishery. To the south west of the reservoir a pumping station is located on the River Exe, upstream of Exebridge, where water is abstracted from the river during times of high flow, stored in tanks and used to supplement levels in the reservoir if required during the summer months.

Due to a renewal of the pumped storage licence, the water company required a programme of aquatic invertebrate monitoring over five years to assess the communities present and to make sure there were no significant changes in their abundances and composition over time. The survey involved extensive sampling in three seasons, spring, summer and autumn, using both semi-qualitative (kick sampling) and quantitative (cyclinder sampling) methods at sites on the rivers Exe and Haddeo, and the River Pulham, a smaller river that joins the Haddeo not far below the Wimbleball dam. Extensive RIVPACS analysis of the data was carried out and showed that over the five year period there was no discernible impact on the biota of the three rivers.