1. River Severn Regulation

2. River Severn Regulation System
Designed and constructed in the 1960’s.
Major component - Llyn Clywedog.
Lake Vyrnwy and Shropshire Groundwater Scheme - phases 1-4 at present.
Operation is governed by a control point 200km downstream of Llyn Clywedog, at Bewdley.
Clywedog - Utilises high rainfall during the winter months in the Welsh Mountains (yearly rainfall of 2000mm). Was built solely for River Severn Regulation as a result of an act of parliament in 1963.
SGWS - In 1970’s it was realised the combined output from C an V alone would not be sufficient to support the R.Severn in dry weather. This was because of increased demands for water use for the R. Severn and the svere drought of 1976.

3. Beneficiaries of River Regulation
Abstractors and Water Companies
Fisheries
Tidal Environments
Navigation
Hydro-electric Power
Recreation
Fisheries - long periods of reduced flows can have effect on river wildlife - release to keep these habitats maintained.
Estuary has second highest tidal range in the world. Saline/sediment intrusion can be combatted by large releases from Clywedog.
HEP - C can generate electricity via HEP to power the release values. If additional electricity is made, it can be sold onto the National Grid.
Recreation - widely used by anglrs/ramblers, canoeists and other boat users. For these users it is important that the amenity value of the river is preserved.

4. River Severn Regulation System
Statutory duty to ensure flows are maintained.
5-day mean flow at Bewdley - 850Ml/d.
Daily mean flow - 650Ml/d at Bewdley.
Additional releases from any regulation source to ensure flows at Bewdley are maintained.
By maintaining Bewdley Flows there is sufficent water for Lower Severn - abstractors - Upton/Mythe and Glous. & Sharpness Canal and nature and wetland reserves

6. Shropshire Ground Water Scheme Lake Vyrnwy
Liverpool
Shropshire Ground Water Scheme
Lake Vyrnwy
Montford
Walcot
Buildwas
Shelton
Wolverhampton & South Staffs.
Llyn Clywedog
Ironbridge PS
Hampton Lode
Birmingham
Dolwen
Trimpley Res
Bewdley
Frankley
Elan Valley Reservoirs
Mythe
Gloucester
Input flow readings/abstractions into Spreadsheet to
forecast the next few days and maintain the level at
Bewdley Gauging Station

7. How do we Regulate?
Monitor Flows at strategic points downstream towards Bewdley.
Follow operating rules - make necessary releases from both reservoirs and groundwater based on current drawdown levels from Llyn Clywedog reservoir.
Monitor abstraction sources upstream of Bewdley -
Shelton, Ironbridge, Trimpley and Hampton Loade

8. How do we Regulate? (2)
Use a spreadsheet tool to calculate predicted recessions at Bewdley.
Lag times from reservoirs/ Met Office rainfall forecasts to calculate Bewdley Flows.
Daily liaison with Hampton Loade operators to discuss predicted and actual abstractions.
Receive daily STW Trimpley abstractions via .
MO - have to coincide releases with lulls in the weather. Frequent minor flood events can allow significant reductions in regulation releases - resource saving. Timing is crucial however. Have to have daily liaison with the Met Office verbally.

9. Release Options
Routine releases of 18.2 Ml/d from Llyn Clywedog, maximum 500Ml/d
45 Ml/d from Lake Vyrnwy depending on local inflows, max 450Mld.
Shropshire Groundwater – maximum 185Ml/d

10. Top part - yesterday’s daily abstraction
Future anticipated abstractions
Chelmarsh reservoir level
Problems with abstractions (i.e. pollution)
Maintenance issues

11. Hampton Loade (2) Ideally …..
We want Hampton Loade to stick to their projected abstraction over the week (hence greyed out boxes for first three days on the fax).
Try to get them to fill Chelmarsh reservoir (bankside storage) so they can use this water during pollution incidents.

12. How Hampton Loade Help us
Can map the 850Ml/d at Bewdley by altering their intake of water by observing the flow at Bewdley using telemetry.
Can use Chelmarsh as secondary regulation. So if flow at Bewdley is close to 850Ml/d they can utilise the bankside storage.

13. Regulation Spreadsheet
Daily Mean
Flow Data
Input
Montford, Walcot,
Buildwas, Bewdley
Flow Data,
daily recessions
& naturalised
flows
Hampton
Loade
demand,
Chelmarsh
storage
Abstractions
upstream of Bewdley
Shelton, Ironbridge, HL,
Trimpley
Actual and Predicted
abstractions
Calculation block
Releases from reservoirs
Predicted recessions at Bewdley
Lagged releases
5-day mean flow and daily flow
Vyrnwy Bank
allocation and
reservoir
storages

14. Naturalised Bewdley flow without influence of
losses from abstractors and inputs from
Reservoirs and groundwater (lagged accordingly)
Combined abstraction from
Trimpley, HL, Ironbridge, Shelton
Daily Mean Flow from Bewdley

15. Based on predicted recessions and lagged response
from water sources we get a predicted daily mean
flow for Bewdley
Spreadsheet then calculates the 5-day mean based on the average
of the 5-daily mean flows as shown previously