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 Abstraction

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David Harvey

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PostSubject: Abstraction   Fri Jun 17, 2011 10:06 am

We have had a huge amount of rain in the last week and I wondered this morning if we will see and river conditions alerts.

http://riverconditions.visitthames.co.uk

The Thames is the main source of drinking water for London so with the extended dry conditions we have had, the abstraction rate is very high. This is normal but why the river will still have little flow.

If you want to know the actual river level in your area, check out this page on the TAC website

http://www.rivertac.org/site/?page_id=725

Tw document

http://www.thameswater.co.uk/cr/water/abstraction-and-low-flows/

Cheers
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Steve Holmes



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PostSubject: Re: Abstraction   Fri Jun 17, 2011 10:37 am

David Harvey wrote:


http://riverconditions.visitthames.co.uk


That site used to be spot on - for the last few weeks though it's been out of date.

As it impacts boating safety, hopefully they'll put pressure on to get it working properly again.
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James Page



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PostSubject: Re: Abstraction   Fri Jun 17, 2011 4:10 pm

my understanding on the grapevine is that levels will remain the same, and that there will be some slight flow
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David Harvey

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PostSubject: Re: Abstraction   Fri Jun 17, 2011 4:36 pm

Cheers for that, thought it must increase a bit. Seems the fish like it Smile
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Andy Banham

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PostSubject: abstraction   Sat Jun 18, 2011 11:05 am

the level stations on the roding and ingrebourne are spot on. i am a E.A critic for past mistakes in my area however being able to check conditions at home where flow/depth on our small rivers outweigh temperture is a great idea hope it continues. Very Happy
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David Harvey

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PostSubject: Re: Abstraction   Mon Jun 20, 2011 4:41 pm

Cheers Andy.

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David Harvey

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PostSubject: Re: Abstraction   Wed Aug 24, 2011 10:21 pm

Me like many others have seen a change in the river again this year. Areas which I have fished for years now have streamer weed where has always been clean gravel. Last night I looked at one marginal spot and found it thick with Canadian pond weed.

So what is the reason, that is an answer we dont have as of yet but with dry winters and a near drought spring, abstraction plays a major part. Whilst extra weed growth in some respects is good, so improving habitat and therefore increasing natural food sources, from an angler it means its not the same river.

Anyway abstraction is high on the radar now and progressing, here is part of the Ten questions we asked Thames Water last year and hopefully gives more of an insight...

Question 1:

The amount of water abstracted from the River Thames has increased to alarming levels. For much of the year the River Thames resembles a lake and there is hardly any flow. Where is water abstracted from on the Thames, how much is abstracted each year by whom, and for what purposes?

Answer 1:

Thames Water abstracts from several intakes (including Datchet, Laleham, Walton and Hampton) under its licence from the Environment Agency (EA) which allows 1818 Ml/d on average over the year. (1Ml/d is one million litres per day). This licence has not been increased since at least 1986. Our abstraction is for public water supply. Other water companies abstract about 400 Ml/d on average and we are not aware of significant abstractions for any other purpose. However, the licensing regime is run by the Environment Agency and they are the only people who could confirm that.

The 1818 Ml/d is an annual average, but there are also strict limits on how much water we have to leave in the river. This is expressed as a residual flow requirement over Teddington weir and is set out in the Lower Thames Operating Agreement (LTOA) between Thames Water and the Environment Agency. We have to allow 800 Ml/d flow over Teddington weir at all times, except when the London reservoirs are drawn down in the summer months. At those times the minimum residual flow is decreased according to the storage in the Thames reservoirs and the time of year. The residual flow is reduced in stages from 800 Ml/d to 600 Ml/d to 400 Ml/d and to a minimum residual flow of 300 Ml/d. In plain language, the lower the reservoirs are, and the earlier in the year this happens, the more serious the risk to London’s water supply, and therefore the more water we can take from the river.

You might like to know that we are undertaking an investigation into the impact of abstraction on the ecology of the lower Thames and the Tideway. This investigation will be complete in 2013 and will be used to determine whether there is adverse impact from the abstraction on the lower Thames.
————-
We have asked for more information about the investigation into the impact of abstraction on the ecology of the lower Thames and the Tideway; hopefully this will be forthcoming

Reply (2/3/10) from Richard Aylard, Director of Thames Water, stating:

All I can really say about the investigation at the moment is that we know we need better information on the impacts of abstraction on the river ecology, in order to have a sensible discussion with the Environment Agency about the future of the Lower Thames Operating Agreement, which in turn will affect our water resource planning. So we have made a case for this work to our economic regulator, Ofwat, and they have just approved it. Now we have to scope the study with the Environment Agency and make sure we look at the right things.
————
Question 2:

How often does abstraction occur, who regulates these abstractions, and how are Thames Water balancing the need to provide drinking water whilst also lessening the impact of abstraction on the natural environment?

Answer 2:

Abstraction occurs all the year round and is regulated by the Environment Agency. The LTOA is set up (as described above) to balance the need to provide drinking water against the need to lessen impact on the environment through the progressive reduction in residual flow as reservoir storage declines and so risk to security of supply increases.

We have a statutory duty to supply water to our customers, and to maintain a balance between supply and demand. Our approach starts with reducing demand, through reducing leakage (after some years of under-achievement we have brought it down by 24% in the last four years), increased metering and encouraging water efficiency. If that doesn’t provide enough water to meet anticipated demand (and bear in mind that London’s population is still growing rapidly) we have to develop new resources. We know we won’t be able to take any more water from the Thames above Teddington weir (and, depending on the results of the survey mentioned above, we may need to take less), so we are about to commission a desalination plant on the tidal Thames at Beckton, for use in times of drought. This abstraction is so far downstream that it will make no difference to the flow in the river. In the longer term, we also have plans to build a major new reservoir near Abingdon, by about 2026. This will abstract water from the upper river during the winter, when flows are high, and store it until it is needed in the summer. We will then release that water back into the river, where it will flow downstream (adding to the natural flow) for abstraction at Datchet, Laleham etc. In addition, we are also looking to develop new ways of pumping surplus winter water underground, to recharge the natural aquifers and give us more to draw on in dry summers. We already do this successfully in parts of North London, but in most places the geology is not suitable.
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PostSubject: Re: Abstraction   Thu Aug 25, 2011 4:24 am

teddington bloody weir
flow over it has been legally decreasing for yonks
no fish study on it for nigh on 20 years
next its hydropower

where's the forward thinking, or is it only used for commercial gain

I can take a narrow boat from the houses of parliament to yorkshire, loads of water there, but strangely I cant get the water from yorkshire to flow down the thames
instead of intending to create a new reservoir, they should engage with their competitors, the other water companies, to get the excess water in the north, flowing down south
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PostSubject: Re: Abstraction   Thu Aug 25, 2011 11:01 am

If, like us, you're just a normal angler and you've never had abstraction on your radar before, this is why it's important...

Abstraction kills more Thames fish every year than poaching, cormorants and pollution put together.

Fry and small fish get sucked in and don't grow into big fish we can catch.

EA fish surveys show big decreases in fish below the abstraction inlets...there's less flow/ oxygen, the river silts up and loads of fish have just been killed a few yards upstream in the inlets.
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David Harvey

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PostSubject: Re: Abstraction   Thu Aug 25, 2011 12:04 pm

Thanks Steve

If I remember, wasnt there a move to change the screens at the inlets.

Also the fish killed just upstream, was there reason given as such.
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Steve Holmes



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PostSubject: Re: Abstraction   Thu Aug 25, 2011 12:13 pm

David Harvey wrote:
Thanks Steve

If I remember, wasnt there a move to change the screens at the inlets.

Also the fish killed just upstream, was there reason given as such.

Sorry mate don't know.

I do remember the EA were looking at strobes in front of the screens which had been proven to scare some fish away. I think they needed testing to see if it worked on all species and what sizes of fish.
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James Page



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PostSubject: Re: Abstraction   Fri Aug 26, 2011 8:12 am

spot on chaps, billions of fish unnecessarily killed every year, and fishing downstream of an intake is a waste of time
what we should be asking is
were sufficient screens installed during the original construction, and why haven't they been updated to a suitable standard
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Ed Randall

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PostSubject: Re: Abstraction   Fri Aug 26, 2011 9:04 am

My guess is we've been down at 300Ml/day since early Spring!
So is there an on-line graph showing the real time flow over Teddington weir somewhere?
The EA must have that data. The boating safe/danger flow table isn't really enough.

I seem to remember asking something like that at the Ham Hydro meeting and being told it wasn't possible because the figures might be inaccuracte or unaudited or some such nonesense.
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PostSubject: Re: Abstraction   Fri Aug 26, 2011 9:14 am

yes there is ed, its in the lockeepers office at teddington
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PostSubject: Re: Abstraction   Sat Aug 27, 2011 5:23 pm

regarding the dry conditions ...

a spot i used to fish in Kingston (around canbury park) used to have around 6inches of water in the margins ... now its gravel , sad to see the Thames (or any river) without water ... soon its going to be a problem for the boaters ,, i fear only then will something be done ... what about us anglers that pay ea licenses ect
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David Harvey

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PostSubject: Re: Abstraction   Sat Aug 27, 2011 11:34 pm

Here's an example of a river that's easy? to manage. Due to rain in Berkshire drenching the site of a famous rock festival, they have dropped the level of the Thames so the water runs quicker of the land....
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