By Paul Homewood
Well, it’s only taken twenty years to sink in!
Water levels in reservoirs should be managed better in order to prevent them overflowing in the future, a Welsh Assembly member has said.
Montgomeryshire AM Russell George said a "failure in operational arrangements" had led to the Clywedog and Vyrnwy reservoirs in Powys overflowing.
The water levels are controlled by the England-based Environment Agency.
The Environment Agency said it was looking at ways of managing water release in the future.
Mr George said: "The recent appalling weather conditions have once again exposed the failure in operational arrangements and flood risk management at Clywedog and Lake Vyrnwy which has resulted in both reservoirs overflowing, the consequence of which has been downstream flooding in both areas.
"The fact that we see continuous overflowing over the top of each reservoirs, demonstrates the lack of control of water discharge."
Both reservoirs are owned and managed by Hafren Dyfrdwy, part of Severn Trent, which said the level of water was "natural" given recent rainfall.
It added: "We could only create spare capacity by releasing water which can only be undertaken at the request of the Environment Agency."
The Environment Agency said it would meet with community representatives to discuss the issues.
It added: "The recent exceptional wet weather has restricted what releases can be made without elevating downstream levels further.
"We are working with Natural Resources Wales and the water companies to look at ways of managing the release of water in future."
https://www.bbc.co.uk/news/uk-wales-51649150
By coincidence, someone sent me this snippet from the Shropshire Star a week or two ago about the flood history of Shrewsbury:
Let’s toy with a few dates which are still within living memory. There was disastrous flooding for consecutive years in 1946 and 1947, the latter being especially terrible because the floods came after the harshest winter for many years.
Fast forward to the 1960s and there were several flood years, but with the 1970s and 1980s being relatively flood-free, a mistaken belief took hold among some folk that the massive reservoirs which had been created in Mid Wales had somehow meant flooding of the River Severn was a thing of the past.
https://www.shropshirestar.com/news/features/2020/02/24/a-dip-into-the-flooding-archives/
It’s that “flood dry” period I have talked a lot about. It is the belief of local experts that it was at that time when the powers that be decided to downgrade the flood control part of the mid Wales reservoirs role and focus wholly on water supply to Liverpool.
As a result, there is always a temptation to keep the dams as full as possible. As the Clean River Trust notes, floods would be much more catastrophic without these reservoirs. Unfortunately this winter The Environment Agency thought it would be a good idea to leave the dams full up before the inundation came:
The river (Severn) rises in the Cambrian Mountains of Powys, high on moorland, a landscape of heather, ling and eroding blanket peat bog, from this bleak height the water quickly drops down tumbling over rocks creating small waterfalls and pools; already developing its valley in miniature and adding to its flow by collecting from many small hillside tributaries. The Severn headwaters are all flash rivers where high rainfall on the hills quickly transfers this water to the river, which as it spates down onto the English midland plain and causes severe flooding. Many reservoirs have been established to both farm this water for supply to the conurbations of the West Midlands and to go someway to regulate the river flow and bring some respite or alleviation of flooding downstream which would be worse than the present catastrophic situation is at present. The waters are contained in Llyn Clywedog, Lake Vyrnwy and Elan Valley reservoirs.
http://www.cleanriverstrust.co.uk/the-river-severn-an-introduction/
It is not an easy call of course. Do you run dam levels down and risk a drought the following summer? But this is where the Met Office should be earning their keep, by giving adequate warning of storms. Unfortunately their 1-month and 3-month outlooks are so pitiably poor as to be useless for planning purposes.
What is clear however is that if Lake Vyrnwy and the other reservoirs had been lowered by a few feet in the weeks leading up to Storm Dennis, much of the flooding down stream would have been avoided.
And exactly the same applies to the S Yorks floods last autumn, as I pointed out at the time, and also the Whaley Bridge Dam spillway failure last summer.
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March 7, 2020 at 08:06AM
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