More than 300,000,000 litres of water will be released over 3 days to aid salmon smolt migration downstream. The Environment Agency asks South West Water, who manage the reservoir with Wessex Water, to release the water.
The release is a mitigation measure resulting from the construction of Wimbleball Lake in the 1970s.
It is particularly useful to do this in the spring, if there are low flow levels, to assist the salmon smolts to move down river towards the sea. This helps encourage them to migrate without delay, protecting them from predation.
Stuart Hunter, for the Environment Agency, said:
To give England’s salmon populations greater resilience, we are working with partners to maximise the output of healthy smolts from our rivers. We recognise that there is much more to be done and we will continue to work with our partners to safeguard England’s salmon populations.
It is through working together that we can give salmon a much needed helping hand. This type of operation is a regular occurrence, along with one in December, to aid upstream fish migration for spawning, and it compensates for the impact to the River Haddeo, a tributary of the River Exe, from Wimbleball reservoir.
This amount of water being released on Exmoor will equate to a rise of just a few centimetres by the time it gets to Exeter. But this is still enough, particularly in periods of prolonged low flows, to give salmon the incentive to move downstream.
We decide when and if the releases will be used. Timing is crucial and is largely dependent on flow and temperature, which dictate when smolts are ready to begin their downstream migration. We also often make a summer release to encourage adult salmon to migrate from the estuary into the river to begin their journey to their spawning grounds in the upper reaches of the River Exe. We make sure that key landowners and users of the river are advised of this release of water before it happens.
James King, Director of Operations, Water Resources and Production, South West Water, said:
We are delighted to be able to assist the Environment Agency in their efforts to support the migration of young salmon in this way. We are in the fortunate position in our region to have a very strong water resource storage position which means plentiful water supplies for customers and the ability to support environmental activities such as this.