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Water Temperature Update

Friday 15th July, 2022

The forecast is looking very hot and sunny from Sunday to Tuesday, but the Wye is currently extremely low. This means that the lives of salmon, which are holed up in the lower reaches, are at risk due to water temperatures becoming fatally high. We can’t change the weather, but we can increase the flow and therefore reduce the risk of ponded pools ‘cooking up.’

Yesterday, the Wye and Usk Foundation came to an agreement with Natural Resources Wales and Welsh Water to use the water within the Elan valley reservoirs to increase the flow in the river. This water needed to be released today for it to be the most effective. Due to the length of the river, this water would require a few days for it to reach the bottom by Tuesday when we expect the situation to be at its most serious. Today’s cooler conditions would also reduce the risk of this release increasing the water temperatures as it flows over scorching rocks. Studies have shown that the cooling effect of a release of this scale will not extend much past Builth, but it will push cooler water from the upper river, downstream. This will help push the hot water at the bottom out.

We had proposed that 1000 million litres per day be released for 2 days from the early hours of this morning to ensure it reached the lower river in time. Discussions between our regulatory bodies, from both sides of the border, delayed the release until 2:30pm. It is also a lower and longer release of 640 million litres per day until 12 noon on Monday. This is an increase of 400 million litres per day or 4.6m3/s for 3 days. The current flow at Monmouth is around 10m3/s.

The water is now on the way but this is less than we asked for. It is especially important that it gets through to the tide and we have been liaising with abstractors to try to ensure this. We are eternally grateful to the Herefordshire farmers who, having had the situation explained, have agreed to reduce and where possible pause entirely their abstractions for crop irrigation at this critical time.

Our thanks to Welsh Water, the farmers, Natural Resources Wales and the Environment Agency for their cooperation in this effort.

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