Eel screens on Water Works intakes

Dave and myself had the chance to visit the Thames Water Works at Walton today, to see the new screens which they have installed on the abstraction intakes.

The works abstracts some 90 million litres/day from the river, pumping it up to the adjacent reservoirs (QEII, Knight and Bessborough).   Overall there is approx. 90 days water supply for London in these and the other large reservoirs around, they are kept topped up.

One consequence of this is that many fish and eels are drawn into the reservoirs, we learned some years back that the lowest biodiverity is found just downstream of these intakes.  The screening on them was just a coarse grid to prevent large sticks etc. going in.  Now as a result of the European Eel directives which have been taken in to UK legislation, any sie abstracting more than 20 cu.metres/day must provide suitable screening to protect eels.

The Walton works have been equipped with fine 1.75mm screens on a rotating mechanism.  At the top there are water jets to de-clog them of leaves, insects etc, these wash out into a channel and back into the river downstream of the intake.


It was a fascinating morning with presentations about the design and construction, and one by Darryl of the EA all about the Eels, followed by a visit to see the screens in operation.

Here is a video about the project which we were shown:


These are going in at all the water works, Laleham, Hampton and Surbiton will be next.  Affinity Water have already screened their intakes using similar technology.

Great news for our great river!

nice

I seldom have anything good to say about Thames water, but here its is a great job and will have a profound effect on not only the Eels but all Juvenile fish that did get drawn into the intakes. Give it time and we could see a real increase in silvers.

All good chaps

The Eel Regs measures are required by law and paid for by the customers of Thames Water. These actually increase water company profits, which are calculated on the basis of capital costs.

See 'Thames Water: the murky structure of a utility company'
https://www.ft.com/content/5413ebf8-24f1-11e7-8691-d5f7e0cd0a16 (paywall - some free pages)

"... under a complex regulatory system, water companies are set a limit on the price they can charge customers based on a combination of operating and capital expenditure. Sir Ian says the system rewards companies for spending money on capital investments whether or not it is in the interest of customers. This often comes at the expense of more mundane operational tasks, such as preventing sewage from seeping into the water, stopping leaks on its 10,000 miles of pipes ..."

“It’s an unholy alliance between politicians and capital markets.”

Water companies (and their staff) have to work with a poisoned chalice handed to them and subsequently maintained by politicians of all the main political parties.
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Screening to protect vastly reduced eel stocks maybe important but does not actually address a likely major cause of the dramatic fall in eel returns - the widespread use of unregulated agrochemicals during past 50+ years, whose use correlates closely here.

The £100s millions being spent on screens nationally may not be enough and helps obscure the real issues here.