FISHING has been suspended across much of the Wye due to the heatwave, while additional water is being released upstream to try to cool it.
The river dries up due to the record temperatures, causing the death of fish.
On Friday, the Wye and Usk Foundation agreed with Natural Resources Wales and Welsh Water to release water from reservoirs in the Elan Valley to increase flow in a bid to reduce Wye’s temperature.
And Glamorgan Anglers, who hold the fishing rights upstream of the Wye Bridge in Monmouth, posted last week: ‘Due to very low water levels and current weather conditions we unfortunately have to close the section of the River Monmouth Wye from Monday July 11 until further notice. .
“We will monitor the situation and reopen the section as soon as conditions improve.”
Salmon and trout fishing is also now suspended on the Usk, after rainfall between March and June fell by more than a third.
Managing director Simon Evans said: “When it comes to fishing it’s the hot water that’s our biggest headache, we already have fish dying in some places.
“The problem is you can’t keep hitting the ecosystem the way we do, we’re oscillating between monster flooding and severe drought, intense heat and monster flooding again.
“And each of these events underscores everything in a new way.”
Water levels are at “basement level” in some sections.
And the foundation posted after its discussions with NRW and WW: “The forecast is for very warm and sunny Sunday to Tuesday, but the Wye is currently extremely low.
“This means that the lives of the salmon, which hide in the lower reaches, are in danger due to the water temperature becoming fatally high.
“We can’t change the weather, but we can increase the flow rate and thus reduce the risk of ‘cooking’ the ponds.
“Yesterday the Wye and Usk Foundation reached an agreement with Natural Resources Wales and Welsh Water to use water from the Elan Valley reservoirs to boost the flow of the river.
“This water needed to be released today for it to be most effective. Due to the length of the river, it will take a few days for this water to reach the bottom by Tuesday when we expect the situation to be at its worst.
“Today’s cooler conditions would also reduce the risk of this release increasing water temperatures as it flows over hot rocks.
“Studies have shown that the cooling effect of a release of this magnitude will not extend much beyond Builth, but it will push cooler water from the upper river downstream. This will help to push the hot water at the bottom out.
“We had proposed that 1,000 million liters a day be released for two days from the early hours of this morning to ensure they reach the lower river in time.
“Discussions between our regulators, on both sides of the border, have delayed the release until 2.30 p.m. It is also a lower and longer release of 640 million liters per day until Monday noon.
“This represents an increase of 400 million liters per day or 4.6 m3/s for 3 days. The current flow at Monmouth is approximately 10m3/s.
“The water is coming now, but it’s less than we asked for. It is particularly important that it passes through the tide and we have been liaising with abstractors to try to ensure this.
“We are eternally grateful to the farmers in Herefordshire who, after being explained the situation, agreed to reduce and, if possible, suspend their crop irrigation levies entirely at this critical time.
“Our thanks to Welsh Water, the farmers, Natural Resources Wales and the Environment Agency for their cooperation in this effort.”
*Conservationists call for a scheme to stop fish-eating birds taking fish from Welsh rivers in a bid to protect stocks, especially young salmon and trout – full story on page 35