Thames Anglers' Conservancy Members Forum
TAC Members-Only Forum
If you have arrived here and not yet signed up as a member, then please first join at http://forum.rivertac.org/register using your real name.

Forum Membership is with Real Names only.
Please create a Username that is your First Name and Surname eg. "Joe Bloggs"
(This will save our Admin team the need to contact you about changing it)

http://rivertac.org/membership


Thames Anglers' Conservancy Members Forum
 
HomeHome  TAC Home PageTAC Home Page  SearchSearch  FAQFAQ  RegisterRegister  Log in  
Navigation
Search
 
 

Display results as :
 
Rechercher Advanced Search
Latest topics
» Thames TideFest 10th September 2017
Yesterday at 11:51 pm by David Harvey

» Eel Trap Results 2017
Yesterday at 11:47 pm by David Harvey

» Do you recognise any of these men?
Sat Aug 19, 2017 8:44 pm by Ed Randall

» Roads closed everywhere ~ July 29th/30th ~ bike race
Wed Jul 26, 2017 9:17 am by Ed Randall

» Better access to free Thames fishing in Reading
Fri Jun 16, 2017 10:08 am by Ed Randall

» Eel screens on Water Works intakes
Tue May 23, 2017 10:26 pm by Julian Jones

» River Thames Conditions - Quick Dial Numbers
Sun May 21, 2017 10:00 am by Ed Randall

» Ap[ril showers? If only! Drought beckons...
Thu May 04, 2017 6:56 pm by Ed Randall

» Abbey river this Saturday (12/5/2012)
Thu Apr 27, 2017 4:41 pm by Ed Randall

» Molesey Eel Monitoring Training ~ 29th April 2017
Mon Apr 24, 2017 11:12 am by David Harvey

» Thames Water fined a record £20m for River Thames pollution
Fri Mar 24, 2017 1:54 pm by Stephen Bond

» Crane Riverfly Training ~ May 6th 2017
Thu Mar 16, 2017 9:08 am by Ed Randall

» TAC visit to Tideway Tunnel Exhibition in Parliament
Wed Mar 15, 2017 7:32 am by John LeSurf

» "Citizen Crane" project - sampling dates
Thu Mar 02, 2017 4:24 pm by Ed Randall

» Egham & Stains bankside enhancement followed by brewery trip
Sun Feb 19, 2017 6:27 pm by Ed Randall

» SE Rivers Trust needs help on Hogsmill
Tue Feb 14, 2017 2:23 pm by Ed Randall

» Crane volunteering opportunities
Fri Jan 27, 2017 5:38 pm by Ed Randall

» Seal (with enormous fish) in Thames near Richmond Lock
Wed Jan 25, 2017 8:34 am by Ed Randall

» [Petition] to eradicate size and catch limits for pike to be taken and culled
Wed Jan 25, 2017 8:27 am by Ed Randall

» *Thames Tunnel (Tideway Tunnel)*
Tue Jan 24, 2017 9:42 pm by Ed Randall

» reels for sale
Thu Jan 12, 2017 9:51 am by JeffHowe

» A new address for 2017 ~ forum.rivertac.org
Sun Jan 01, 2017 11:06 am by Admin

» New users - Registration issues
Thu Dec 29, 2016 11:47 am by Ed Randall

» Shepperton river death - Van removed near Dockett Eddy Lane
Thu Dec 22, 2016 9:54 am by Ed Randall

» EA Pollution incidents: 2015 evidence summary
Mon Nov 21, 2016 5:04 am by David Harvey

» Ham & Petersham cleanup Saturday 19th Nov
Sat Nov 12, 2016 6:01 pm by Ed Randall

» LIVE THAMES TEMPS AND CLARITY - TAC exclusive!
Thu Nov 10, 2016 9:51 pm by Stephen Bond

» Citizen Crane Forum at ZSL - Mon 14th Nov 2016
Thu Nov 10, 2016 8:36 am by Ed Randall

» fishing trolleys
Sun Oct 30, 2016 11:23 am by Harry Notley

» Draw off 2016
Sat Oct 29, 2016 2:24 pm by Ed Randall

Angling Data View
River Levels
UK Map

Thames Tides

Share | 
 

 Water Abstraction, inter river transfer, and their effects

View previous topic View next topic Go down 
AuthorMessage
Chris Daphne
Committee
Committee
avatar

Male Posts : 141
Join date : 2010-01-28
Location : Highlands of Scotland

PostSubject: Water Abstraction, inter river transfer, and their effects   Fri Mar 26, 2010 12:19 am

Thought i would just write a bit about the above.

Abstraction

Simplest method involves placing a pipe in a stram and diverting some of the water down the pipe under gravity to a supply point. - Frequently used in rural areas with little effect on the aquatic environment as long as a small proportion of the flow is abstracted.

For a larger community - a lake is usually tapped into. A sluice or dam is built at the outflow to control water levels. This may impede fish movement on a migratory system unless a fish pass is built into the outflow.

Where no pond/lake is available then reservoir construction may be necessary. In its simplest form- a small catchment in a hilly area is trapped by a small dam and water diverted to a supply point with the exception of a compensation flow which passes downstream to maintain the stream environment. Again there are few environmental problems although there may be objections should the scheme flood an area of scientific interest.

Large reservoir formation means impounding the upper reaches of a river in an area of high rainfall and diverting water directly to the demand area ( Direct Supply) This may mean water is piped a large distance and may not be returned to the river. Or it may be used within the catchment and returned lower down the river but with reduced quality.
This type of system has many environmental problems - changes in flow, water temperature, water quality, obstruction, delay to migratory fish and flooding of spawning and nursery areas.

A reservoir may be sited close to a river and kept full by pumping from the river when the flow is adequate. The reservoir water may be used to supply a nearby town - Oxford from Farmoor reservoir. It may be used to supply towns that are a good distance away like Grafham. If the supply is used close to the river and the effluent returned then there may be little effect. When the supply is used outside the catchment there may be problems like the ones previously mentioned. More problems arise if the water is pumped to towns upstream and the effluent returned to the river so that some of it may be pumped into the reservoir. This recycling may accelerate Eutrophication - Effluent from Milton Keynes recycles into Grafham

Another type of reservoir which are of greater value to a river are "Regulating reservoirs". Water is released from the reservoir during periods of low river flow and abstracted downstream at the point of demand. The flow is regulated, flood flows are reduced due to some of it being impounded and drought flows increased due to supplementation. When water is required for abstraction a compensation flow is discharged to maintain the river.
Environmental problems still occurr, the river is no longer natural. Large fluctuations in river levels may occur. There may be insufficient flow to scour the river bed of silt and weed growth and assist migratory fish. Lower flows may exist below the abstraction point.

Another method is to pump water directly from the lower reaches into a storage reservoir. The river is left in a natural state until the last minute. This scheme can only operate if the water is reasonably pure and where treatment facilities exist. This is the case with LONDONS SUPPLY FROM RESERVOIRS AT STAINES AND BARNES TAKING WATER FROM THE THAMES AND LEE.

A system was developed by the old Thames Conservancy of pumping water from boreholes but the water into into rivers and using these as aqueducts to carry water to towns - Lambourn and Kennet supply water to Metropolitan London. The punping augments summer flows and may be beneficial as long as the boreholes are not overexploited. This danger point has now been reached and the system is under review.

All the above schemes are relatively simple and involve single rivers. For future demand a more integrated strategy is required - this is best achieved by INTER RIVER TRANSFER from one river to another. This has many biological, physical and chemical impacts on both rivers.

Effects of Water Transfer
In some cases the amount of water from the donor will be more than the average daily flow of the recipient leading to flood conditions leading to a need for channel modification. Enlarging the recipient channel could mean the destruction or improvement of the existing fishery or create a new fishery. Fish and food webs require specific conditions to survive. Fish will not remain where there is insufficient depth or cover. A straight trapezoidal channel with steep sides and evenly graded provides little or no cover and is poor habitat. A winding channel cut with one or more lateral shelves ( Berms ) deepened on bends and with natural cover will rehabilitate as natural scour takes place.
Seasonal transfers can be beneficial to fisheries such as in drought conditions on the recipient river. The rate of the introduced flow is important, sudden deepening may occurr or a sudden reduction may strand fish.
Changes in flow velocity- will affect river bed stability, sedimentation, survival of rooted plants and invertebrates, river channel habitats and the bankside habitat. Suspended solids may be increased leading to smothering, increased turbidity which will affect plant growth.
Changes in water temperature - A river recieving water from a reservoir may undergo severe temperature fluctuations if the water is drawn from the hyperlimnion in a stratified water body.

River transfers in Britain tend to be from NW to SE. This means soft water is moved into a hard water area. If the donor water carries pollutants or has the capacity to affect pollutants already present in the recipient river. Changes in PH are important as this may increase the toxicity of ammonia and metal cyanides.
Biological problems - Transfer of fish diseases and parasites, invertebrates, phytoplankton, macrophytes and fish.
Back to top Go down
James Page



Posts : 2153
Join date : 2010-01-21

PostSubject: Re: Water Abstraction, inter river transfer, and their effects   Tue Apr 20, 2010 8:15 am

that's brill bro, or, just the ticket in my case, cheers buddy
Back to top Go down
Richard Crimp
Admin
Admin
avatar

Male Posts : 1875
Join date : 2010-01-20
Age : 51
Location : London

PostSubject: Re: Water Abstraction, inter river transfer, and their effects   Tue Apr 20, 2010 11:14 pm

Very interesting Chris, and although I've read about water transfer before, it is nice to see it in a condensed form that is relativly easy to understand.

Thanks,


Richard Cool
Back to top Go down
Sponsored content




PostSubject: Re: Water Abstraction, inter river transfer, and their effects   

Back to top Go down
 
Water Abstraction, inter river transfer, and their effects
View previous topic View next topic Back to top 
Page 1 of 1
 Similar topics
-
» The Gambia - Sun,Sea and Small Fish
» River in flood. How To Proceed?
» Tamworth & District
» Kingsbury Water Park
» Water Tanks

Permissions in this forum:You cannot reply to topics in this forum
Thames Anglers' Conservancy Members Forum :: Open Section :: Conservation Issues-
Jump to: