Thames Water Severn Thames Transfer Water quality and ecology - - PowerPoint PPT Presentation

Thames Water Severn Thames Transfer

Water quality and ecology assessment: Phase 2 2nd Stakeholder Sub-Group Meeting May 6, 2015

From policy to practice

09:30 Arrival and coffee 10:00 Session 1: Welcome and Review of Background

• Introduction (Chris)
• Review of Phase 1 (Kieran)
• Work completed to date (Kieran)
• Summary of key points (Kieran)

11:30 A short break for refreshments 11:40 Session 2: Hydrology

• Operational hydrology findings (Trevor)
• Discussion of findings to date and update on next steps with flow studies (All)

Session 3: Water Quality

• Water quality data assessment (environmental and drinking water quality) (Trevor)
• Risks or potential showstoppers from comparative WQ data analyses (All)

12:45 Lunch 13:15

• HR Water quality model flow components - calibration and validation results (Andy/Valerie)
• HR water quality modelling calibration and verification update (Andy/Valerie)
• Consideration of key issues from WQ modelling (All)

14:30 A short break for refreshments 14:40 Session 4: Ecology

• Description of how ecological assessment will be undertaken (Rob/Trevor)
• Baseline ecological descriptions and risk characterisation (Rob)
• Discussion of overall reporting structure (Rob)
• Next steps

15:30 Close and depart

Agenda

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Session 1 – Welcome and Review of Background

Summary of Phase 1

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Water Quality

• High Risk: Phosphorus, Algae, Metaldehyde, Bromide, Cryptosporidium
• Moderate Risk: Copper, Zinc, Nitrates and Nitrites
• Low volume (100Ml/d) transfers via Culham or Lechlade unlikely to present

risk to compliance

• From water quality perspective transfers to Cricklade are least viable options

Ecology

• Ecological impacts on River Severn assessed to be low.
• Moderate/high risk to Thames fish during a dry year.
• Moderate risk to Thames macroinvertebrates during dry year.
• Low/moderate risk to Thames ecology during average year.

Topics set out for Phase 2 in the Interim Report

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

River water quality Ecology Drinking water source quality

• Water temperature changes
• Turbidity/fine sediment
• Nutrients (phosphate, silicate)
• Toxics (including WFD Annex 8

and 10)

• Overall water chemistry (e.g.

pH, hardness)

• Other WFD physico-chemical

status (dissolved oxygen, ammonia)

• Invasive non-native species

(INNS)

• Fish parasites
• Genetics (fish)
• Phytoplankton
• Eels
• Mussels (BAP 1)
• Designated sites
• Distinct habitat
• WFD fish status
• WFD invert status
• WFD plant status
• WFD diatom status
• Bromide
• Cryptosporidium
• Metaldehyde
• Colour
• Total organic carbon
• Nitrate
• Pesticides
• Metals (copper, zinc, iron)

Severn Thames Transfer Water quality and ecology assessment Phase 2

Vyrnwy Reservoir 1 2 3 Abstraction Locations

• Saul’s Junction on Gloucester &

Sharpness Canal

• River Severn at Deerhurst to direct

pipeline

• River Severn at Uckinghall to

Longdon Marsh reservoir 1 2 3 Longdon Marsh reservoir Severn Estuary Release Locations

• Cricklade
• Lechlade (canal)
• Culham

A B C A B C Abstraction locations Thames Tideway Canal transfer route River Thames

Phase 2 Variant Scope

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Variant Transfer route Abstraction rate from Severn - up to (Ml/d) Transfer capacity and Thames release rate - up to (Ml/d) Supporting reservoir capacity (Mm3) River Severn abstraction location River Thames release location Bankside storage for settlement (pre-treatment) Sweetening flow minimum (Ml/d) 1 Unsupported, transfer by Deerhurst pipeline Deerhurst (Pressurised to Winchombe break pressure tank (23.5km), then by gravity to discharge location [Culham 61km]) 100 100 n/a Pipeline intake at Deerhurst Cricklade or Culham (potentially anywhere between) Likely to be required 2.5 2 200 200 n/a 5 3 300 300 n/a 10 4 Unsupported, transfer by canal Gloucester & Sharpness Canal Cotswold Canals: Stroudwater Navigation to Stroud, then Severn Thames Canal from Stroud to Inglesham (60km) 50 50 n/a Gloucester Docks/ Saul’s Junction Inglesham (near Lechlade) Unlikely to be required n/a 5 100 100 n/a 6 Supported, transfer by Deerhurst pipeline Route as per Deerhurst pipe above 900 200 50 Intake at Uckinghall to reservoir Deerhurst Cricklade or Culham (potentially anywhere between) Unlikely to be required?? ~7 7 900 600 125 ? 8 Supported, transfer by canal Includes regulation releases into lower Severn. Canals as above 900 50 ? Uckinghall to reservoir Gloucester Docks/ Saul’s Junction to canal Inglesham (near Lechlade) Unlikely to be required?? n/a 9 900 100 ? 10 Phased Canals as above 50 50 ? As for canal variants above Inglesham (near Lechlade) Unlikely to be required?? n/a 11 100 100 ? 12 Pipeline from Severn at Deerhurst 100 100 ? As for pipeline options above Cricklade or Culham (potentially anywhere between) Likely to be required for pre- support reservoir phase 2.5 13 200 200 ? 5 14 300 300 ? 10 15 Other supported (Vyrnwy,STW effluent transfer) As for pipeline and canal options As above 50 to 3001 n/a As for pipeline and canal options Cricklade, Lechlade

• r Culham

Likely to be required

Strategic Priorities for the Phase 2 Investigation, and its Context

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• To provide input to the requirement to further develop our understanding of

major water resource options to inform WRMP19

• To provide improved understanding of the WQ and Ecology issues

associated with the potential Severn to Thames transfer option More Specifically :

• To address the requirement to investigate the WQ and ecological impacts of

the Severn to Thames transfer

• To deliver Phase 2 of the WQ and Ecology Investigation building on the

findings and recommendations of Stage 1 meeting the requirements of the Terms of Reference

• To meet the specific study objectives

Work Completed to Date

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Extensive data collation process
• Review of data, previous studies and scope of assessment
• Issued Interim Report (16/09/14)
• River Thames mussels and invasive species survey Cricklade to Lechlade
• Issued Operating Conventions Paper (07/11/14)
• Extended Severn model, then combined with the Jubilee and Thames models
• Model calibration and validation review undertaken
• Run first set of model scenarios, currently being revised
• Drinking Water Risk Assessment Methodology to other water companies

(issued this week)

• Baseline assessments for hydrology, WFD, drinking water, fisheries, protected

species and invasive species almost complete

• Produced proposed draft report structure.

Phase 2 Approach

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Water quality and flow modelling Ecology risk assessment Drinking water safety assessment Water quality baseline characterisation Hydrology characterisation and assessment Water quality risk assessment Future baseline Future baseline Drinking water safety baseline (Drinking Water Safety Plans) Ecology baseline characterisation Calibration/Validation Consideration of mitigation and cost Scenario testing including alternative futures

Severn Thames Transfer Water quality and ecology assessment Phase 2

11:30 - Morning Break

From policy to practice

Severn Thames Transfer Water quality and ecology assessment Phase 2

Session 2 – Hydrology

From policy to practice

Requirements of Operational Hydrology Assessment

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Provision of supporting hydrology information to ecology and water quality

characterisation and assessment

• Identification of when, how often and for how long could transfer be required?
• Characterisation of the flow conditions in the River Severn and River Thames.
• Consideration of level of hydrological sensitivity based on transfer triggers
• What could River Severn flow change to - where and when with assessment of

difference vs normal range. Consideration of hydraulics (for ecology)

• What could River Thames flow change to – where and when with assessment of

difference vs normal range. Consideration of hydraulics and backwaters (for ecology)

Two Indicative Operating Conventions

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

A. Indicative operating convention based around an existing trigger line on reservoir storage and an additional flow condition B. Indicative operating convention based around a potential additional trigger line

• n reservoir storage

Application of indicative operating convention A to a stylised typical year Application of indicative operating convention B to a stylised typical year

Reservoir storage trigger

Update on Next Steps with Flow Studies

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Awaited:

• 1920-2010 lower River Severn flow series to be completed (by HR Wallingford)
• Water Resources modelling undertaken for baseline and each option using the two

indicative operating conventions (by Thames Water) Next steps:

• Completion of baseline characterisation of river flows in the study area
• Assessment of general transfer requirement pattern for each of the two indicative
• perating conventions
• Assessment , for each option, of the:
• Transfer pattern (volume, timing (season and duration), regularity)
• Resultant (lower or neutral) flows in the lower River Severn
• Resultant (higher) flows in the River Thames at selected locations
• Incorporation of flow assessment findings into water quality and ecological

assessment of scheme variants.

Severn Thames Transfer Water quality and ecology assessment Phase 2

Session 3 – Water Quality

From policy to practice

Environmental water quality data analysis: Overview

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Water quality assessment considers likely impacts on river water quality and

subsequent risks to the different abstraction and discharge areas.

• Likely changes in river water quality considered against a baseline of current river

water quality in River Severn and River Thames.

• Assessment takes account of extent of deviation from Good Ecological Status (GES) /

Good Ecological Potential (GEP) and relevant WFD quality standards

• All potential variants of transfer scheme considered, with varying levels of assessment

proportionate to level of current and future risk.

• Drinking water quality considered separately against Drinking Water Safety Plans.

WQ data analyses: Baseline approach

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

General:

• 1. pH
• 2. Dissolved oxygen
• 3. Temperature
• 4. Biochemical Oxygen

Demand

• 5. Ammonia
• 6. Turbidity
• 7. Suspended solids
• 8. Alkalinity
• 9. Dissolved organic

carbon

• 10. Colour
• 11. Conductivity
• 12. Chlorophyll a

Nutrients:

• 1. Reactive phosphorus
• 2. Silicate
• 3. Nitrate.

Phase 2 Water Quality parameters WFD Physico-chemical substances WFD Specific Pollutants (Annex VIII) WFD Priority Substances (Annex X) Heavy metals:

• 1. Copper
• 2. Zinc
• 3. Iron
• 4. Chromium
• 5. Mercury.

Pollutants:

• 1. Bromide
• 2. Bromate
• 3. Metaldehyde
• 4. Phenols
• 5. Total pesticides
• 6. Tributyltin.

WQ data analyses: Baseline approach

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

WQ data analyses: Baseline approach

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Environment Agency data used for River Thames and River Severn Bristol Water data used for Gloucester & Sharpness Canal. Site selection criteria:

• Proximity to abstraction/discharge location, including other influences
• Length and completeness of dataset available (2003-2013), including suite of

determinants

• For incomplete datasets, sites were combined. Statistical testing for differences

undertaken for each determinand prior to combining sites:

• Downstream of Cricklade two available sites but statistically significantly

different – the site closest to the outlet was selected.

• Severn upstream of Uckinghall and Thames downstream of Lechlade and

Culham, data was not significantly different –sites were combined for robustness and completeness

WQ data analyses: Baseline approach

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

WQ data analyses: Baseline approach

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Baseline water quality data reviewed to determine:

• Extent of variability and spatial patterns: i.e. between sites on River Severn and River

Thames and between proposed abstraction and discharge locations

• Seasonal variability
• Variability with flow, including wet vs dry years
• Long term trends based on 10-year dataset (2003-2013) and extent of deviation

from GES/GEP

• Baseline characterisation used to assess change indicated by modelled scenario runs.

Approach to assessing variability in environmental water quality

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

5% outliers 5% Outliers 95 percentile Quartile 3 – 75% Quartile 2 – 50% (Median) Quartile 1 – 25% 5 percentile

Severn Sites: Blue – Upton, Red – d/s Uckinghall, u/s Deerhurst, Gold = d/s Deerhurst, u/s G&S Canal

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Raw data points Running mean line – based on 1yr of data Approach to characterising seasonal and longer term variability in environmental water quality

Approach to characterising water quality variability with flow

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Top 10% ‘wettest year’ Flow statistics were used to categorise low flow, typical flow and high flow years. Also, concentrations typically higher down the catchment compared to upper reaches Top 10% ‘driest year’ Top 10% ‘driest years’ Top 10% ‘wettest year’ Example: Suspended solids in the River Severn

WQ data analyses: pH

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham

WQ data analyses: dissolved oxygen

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

No data available No data available Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham

WQ data analyses: temperature

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham

WQ data analyses: suspended solids

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

No data available No data available Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham

WQ data analyses: chlorophyll a

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

No data available No data available Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham

WQ data analyses: soluble reactive phosphorus

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

No data available No data available Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham

WQ data analyses: ammonia

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

No data available No data available Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham

WQ data analyses: nitrate

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

No data available No data available Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Acidity (pH) comparable between catchments
• Dissolved Oxygen typically high and comparable between catchments
• Temperature comparable between catchments
• Ammonia comparable between Severn and Thames at Cricklade and Lechlade, but

higher at Culham

• Chlorophyll a higher in Severn compared to Thames at Cricklade, but comparable

between the Severn and Thames at Culham

• Suspended solids higher in Severn compared to Thames, positive relationship with

wetter years

• Soluble Reactive Phosphorus showing reduction in concentration over time, slightly

higher in Severn compared with Lechlade and Culham, Cricklade more variable of Thames sites

• Nitrate displaying seasonal variability and higher in Gloucester & Sharpness Canal

compared to Severn and Thames, Severn and Thames comparable Environmental water quality baseline findings

Review of Phase 1 findings against Phase 2 initial environmental water quality work

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Water Quality

• High Risk: Phosphorus, Algae, Metaldehyde, Bromide, Cryptosporidium
• Moderate Risk: Copper, Zinc, Nitrates and Nitrites
• Low volume (100Ml/d) transfers via Culham or Lechlade unlikely to present

risk to compliance

• From water quality perspective transfers to Cricklade are least viable options

Next steps

• Detailed assessment through water quality modelling, linked to variants

through hydrology assessment

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Under Water Industry Act 1991 (amended by Water Act 2003) Thames Water has

statutory requirement to ensure that risks to drinking water quality are adequately managed.

• Assessment considers likely impacts on drinking water quality and the subsequent

risks to abstractors at relevant locations in study area

• Likely changes in drinking water are being considered against a baseline of current

drinking water quality risks, as summarised in the appropriate water company Drinking Water Safety Plan(s) (DWSP).

• All potential variants of transfer will be considered, with varying levels of assessment

proportionate to level of current and future risk. Drinking water quality data analysis: Overview

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Drinking Water Quality analysis: Approach

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• 1. Alkalinity
• 2. Bromate
• 3. Conductivity
• 4. Sodium
• 5. Carbetamide
• 6. Metaldehyde
• 7. Sulphate
• 8. Magnesium
• 9. Propyzamide
• 10. Turbidity
• 11. Clopyralid
• 12. Colour
• 13. Mecoprop
• 14. pH
• 15. Chloride
• 16. Calcium
• 17. Total dissolved solids*
• 18. Cryptosporidium*

*not yet assessed

Part A: What are the likely substances?

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Part B: Are there any differences in source quality and intake quality? B1 - Primary screen for each substance for all sources and intakes with removal of substances without risk. B2 - Secondary screen for all remaining substances for all sources, reducing uncertainty by incorporating likely flows and seasons that the scheme would

• perate, with removal of substances without risk.

Part C: What is the extent of change in drinking water safety risk? Remaining list of 'risk' substances is assessed for drinking water safety risk for each transfer variant and operating scenario. Current DWSP red-amber-green categorisation of risks, as set out at the catchment scale, will provide the baseline. General evidence from the secondary screen will be used to inform possible category changes that may associate with a transfer

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Metaldehyde: Phase B1 – Demonstration of approach

• 90th percentiles within PCV for all sites (2004-2014).
• PCV exceedances at all sites, in particular Purton
• No data available at Haw Bridge (representative of Deerhurst)

All sites screened-in to Phase B2 (subject to data availability)

Severn Thames Transfer Water quality and ecology assessment Phase 2

Metaldehyde: Phase B2 – Demonstration of approach

Mythe WTW Purton Datchet Farmoor

Flows most likely that scheme will operate in Concentration range most likely to be transferred based on flow range

Drinking water quality analysis

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Drinking water quality analysis

Magnesium Sulphate Propyzamide Turbidity Clopyralid Colour

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Drinking water quality analysis

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Summary of Drinking Water findings to date

• 16 of 18 initial substances have been assessed to date. Screening assessment of

cryptosporidium and total dissolved solids to be undertaken in due course.

• Safe to screen out some substances at phase B1 based on measured concentrations

against PCV across all sites

• At least 7 substances require assessment in Phases B2/C2
• Pesticide exceedances common across all sites (namely Carbetamide, Metaldehyde,

Propyzamide, Chlorpiralid and Mecoprop)

• Colour/turbidity exceedances also common
• Varied data availability between sites limits definitive conclusions for some

substances.

Review of Phase 1 findings against Phase 2 initial drinking water quality work

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Water Quality

• High Risk: Phosphorus, Algae, Metaldehyde, Bromide, Cryptosporidium
• Moderate Risk: Copper, Zinc, Nitrates and Nitrites
• Low volume (100Ml/d) transfers via Culham or Lechlade unlikely to present

risk to compliance

• From water quality perspective transfers to Cricklade are least viable options

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Drinking Water Quality Next steps

• Agree full suite of substances and those which are screened in/out
• Confirm current DWSP risk at each WTW (from recently revised DWSPs)
• Establish the envelope of changed of DWSP risk from a transfer against the baseline

in the appropriate water company Drinking Water Safety Plan(s) (DWSP).

• Seek agreement on the approach with relevant water supply companies (namely

Severn Trent Water, Bristol Water, Affinity Water and South East Water) on:

• inclusion/ exclusion of certain substances of interest
• establish their preferred level of involvement going forward.

Model calibration and validation

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn flow calibration and validation

Deerhurst Haw Bridge

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn WQ calibration and validation

Ashleworth Severn footbridge Chaceley Stock Haw Bridge Westgate Bridge Maisemore Weir

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

River Severn calibration & validation

• Overview
• Calibration and validation of flows is good
• Calibration and validation of water quality is as good as

possible

– Model replicates magnitude of concentration and general trends – Model produces some peaks and lows in concentration that are not picked up by monitoring – Model does not replicate monitoring outliers – are the outliers accurate readings? – Strong fits: » BOD, PO4, TON, Temp, Ammonia, Silicate – Weaker fits: » Zn, Cu, Chl, SS, DO

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn location 2007 2010 2011 Deerhurst 0.91 0.87 0.98 Haw Bridge 0.88 0.89 0.95

Flows - Nash-Sutcliffe efficiency Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Thames location 2003 2004 2011 Farmoor 0.85 0.70 0.79 Maidenhead 0.93 0.78 0.84 Reading 0.97 0.80 0.95 Staines 0.96 0.83 0.87 Sutton Courtenay 0.98 0.96 0.99 Teddington 0.94 0.76 0.88 Walton 0.94 0.77 0.83 Windsor 0.80 0.90 0.90

Deerhurst flows Issue with

• bserved data

2007 2010 2011

Severn location 2007 2010 2011 Deerhurst 0.91 0.87 0.98

Nash-Sutcliffe efficiency

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Haw Bridge flows 2007 2010 2011

Severn location 2007 2010 2011 Haw Bridge 0.88 0.89 0.95

Nash-Sutcliffe efficiency

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Ashleworth WQ 2011 PO4 (mg/l) Cu (ug/l) Silicate (mg/l) Zn (ug/l) Good fits Weaker fit

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Haw Bridge WQ 2010 SS (mg/l) TON (mg/l) Good fits Ammonia (mg/l) Chl (mg/l)

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Maisemore Weir WQ 2007 BOD (mg/l) DO (mg/l) DO (% sat) Temp (˚C) Good fit

• k
• k

Good fit

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Upper Thames flow & WQ calibration and validation

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Lower Thames flow calibration and validation

Sutton Courtenay Windsor Reading Maidenhead Staines Teddington Walton

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Lower Thames WQ calibration and validation

Donnington Bridge Radley Sutton Bridge Wallingford Caversham Weir Boveney Weir Walton Teddington

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

River Thames calibration & validation

• Overview
• Calibration and validation of flows is generally good
• Calibration and validation of water quality is as good as

possible

– Model replicates magnitude of concentration and general trends – Model produces some peaks and lows in concentration that are not picked up by monitoring – Model does not replicate monitoring outliers – are the outliers accurate readings? – Goodness of fit varies from site to site for the same parameter – Strong fits: » BOD, DO, SS, PO4, Temp, Ammonia, Silicate – Weaker fits: » Chl, TON, Zn, Cu

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Farmoor flows 2003 2011 2004

Thames location 2003 2004 2011 Farmoor 0.85 0.70 0.79

Nash-Sutcliffe efficiency

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Teddington flows 2003 2011 2004

Thames location 2003 2004 2011 Teddington 0.94 0.76 0.88

Nash-Sutcliffe efficiency

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Farmoor WQ calibration 2003 BOD (mg/l) DO (mg/l) DO (% sat) Temp (˚C) SS (mg/l) Chl (mg/l) Good fits Weaker fit

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Farmoor WQ calibration 2003 Good fits PO4 (mg/l) TON (mg/l) Ammonia (mg/l) Zn (ug/l) Cu (ug/l) Silicate (mg/l)

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Farmoor validation 2011 Good fits BOD (mg/l) DO (mg/l) DO (% sat) Temp (˚C) SS (mg/l) Chl (mg/l) Weaker fit

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Farmoor validation 2011 Good fits TON (mg/l) Ammonia (mg/l) PO4 (mg/l) Silicate (mg/l) Cu (ug/l) Zn (ug/l) Weaker fit

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Teddington WQ calibration 2004 Good fits BOD (mg/l) DO (mg/l) DO (% sat) Temp (˚C) SS (mg/l) Chl (mg/l) Weaker fit

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Teddington validation 2011 Good fits TON (mg/l) Ammonia (mg/l) PO4 (mg/l) Silicate (mg/l) Cu (ug/l) Zn (ug/l) Weaker fit

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Water quality modelling results

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Modelled scenarios

Variant

• R. Severn abstraction location
• R. Thames discharge location

3a Unsupported via pipeline 300 Ml/d Pipeline intake at Deerhurst Cricklade discharge 3b Unsupported via pipeline 300 Ml/d Pipeline intake at Deerhurst Culham discharge 5 Unsupported via Canal 240 Ml/d Intake to canal at Gloucester Docks / Saul’s Junction Inglesham (near Lechlade) 7a Supported via pipeline 600 Ml/d Intake at Uckinghall reservoir Transfer directly from reservoir via pipeline Cricklade discharge 7b Supported via pipeline 600 Ml/d Intake at Uckinghall reservoir Transfer directly from reservoir via pipeline Culham discharge 9 Supported via Canal 240 Ml/d Intake at Uckinghall reservoir Intake to canal at Gloucester Docks / Saul’s Junction Inglesham (near Lechlade)

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Assumptions

• River Severn
• The transfer runs every model time step when flow > HOF

– HOF 1 = 1,800 Ml/d – no abstraction – HOF 2 = 2,490 Ml/d – abstraction limited to 240 Ml/d

• No impact on the main River Severn for unsupported canal variant

(5)

• River Thames
• The transfer runs every day in 2011
• Pipeline transfer – WQ of the previous day (-24 hours) from the

Severn is added to the Thames to allow for transfer time

• Canal transfer - WQ of the previous week (-7 days) from the

Severn is added to the Thames to allow for transfer time

• Supported variants – simple calculation to take account of long

reservoir residence time Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Results locations

Severn Thames Uckinghall Cricklade  Mythe  Lechlade  Deerhurst  Farmoor  G & S canal intake  Culham  Caversham Weir Bray Sunnymeads and Datchet Staines and Egham Laleham Chertsey Walton (Affinity Water abstraction) Walton (Thames Water abstraction)  Teddington 

 Results presented in slides

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

WQ parameters Complete In progress Temperature Metaldehyde Suspended solids Bromide BOD  Organic nitrogen Dissolved Oxygen  Ammonia  Total Oxidised Nitrogen (TON)  Orthophosphate  Silicate Chlorophyll Cu Zn  Cryptosporidium – not included in model Results presented in slides 

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Results overview

• River Severn
• Minimal change from baseline WQ at Mythe, Deerhurst and the G&S canal intake
• River Thames
• Cricklade

– Scenarios > baseline for Zn – Scenarios < baseline for TON, PO4

• Lechlade

– Scenarios > baseline for Zn – Scenarios < baseline for BOD, Ammonia, TON, PO4

• Farmoor

– Scenarios > baseline for Zn – Scenarios < baseline for TON, Ammonia

• Culham, Sunnymeads & Datchet

– Scenarios > baseline for Zn – Scenarios < baseline for TON, Ammonia – Scenario 7 < baseline for PO4, BOD

• Walton (Thames Water abstraction)

– Minor change from baseline WQ – Scenarios < baseline for TON, PO4, Ammonia

• Teddington

– Scenarios < baseline for TON, PO4

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Mythe BOD (mg/l) PO4 (mg/l) Cu (ug/l) Zn (ug/l) TON (mg/l) Chl (mg/l) Minimal change from baseline WQ

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Deerhurst BOD (mg/l) PO4 (mg/l) Cu (ug/l) Zn (ug/l) TON (mg/l) Chl (mg/l) Minimal change from baseline WQ

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn G&S canal intake BOD (mg/l) PO4 (mg/l) Cu (ug/l) Zn (ug/l) TON (mg/l) Chl (mg/l) Minimal change from baseline WQ

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Thames Cricklade BOD (mg/l) PO4 (mg/l) DO (mg/l) Zn (ug/l) TON (mg/l) Ammonia (mg/l) Some changes from baseline WQ

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Thames Lechlade BOD (mg/l) PO4 (mg/l) DO (mg/l) Zn (ug/l) TON (mg/l) Ammonia (mg/l) Some changes from baseline WQ

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Thames Farmoor BOD (mg/l) PO4 (mg/l) DO (mg/l) Zn (ug/l) TON (mg/l) Ammonia (mg/l) Some changes from baseline WQ

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Thames Culham BOD (mg/l) PO4 (mg/l) DO (mg/l) Zn (ug/l) TON (mg/l) Ammonia (mg/l) Some changes from baseline WQ

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Thames Sunnymeads & Datchet BOD (mg/l) PO4 (mg/l) DO (mg/l) Zn (ug/l) TON (mg/l) Ammonia (mg/l) Some changes from baseline WQ

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Thames Walton (TW abstraction) BOD (mg/l) PO4 (mg/l) DO (mg/l) Zn (ug/l) TON (mg/l) Ammonia (mg/l) Some changes from baseline WQ

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Thames Teddington BOD (mg/l) PO4 (mg/l) DO (mg/l) TON (mg/l) Ammonia (mg/l) Some changes from baseline WQ Cu (ug/l)

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Longitudinal variation Ammonia (mg/l) PO4 (mg/l) Flow (Ml/day)

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Overall findings

• River Severn
• Minimal change from baseline WQ
• River Thames
• There are some changes from baseline WQ
• These changes diminish in the downstream reaches of the Thames

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Thames Transfer Water quality and ecology assessment Phase 2

14:30 – Afternoon Break

From policy to practice

Severn Thames Transfer Water quality and ecology assessment Phase 2

Session 4 – Ecology

From policy to practice

Severn Thames Transfer Water quality and ecology assessment Phase 2

Ecology - WFD

From policy to practice

WFD: Overview

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• WFD work reviews status of WFD waterbodies in the Severn and Thames over time,

using reported status (RBMP1) and interim status updates.

• Will consider likely impacts on WFD status, achievement of Good Ecological Status

(GES)/Good Ecological Potential (GEP) in each WFD waterbody and if scheme has potential to prevent waterbodies from achieving GES/GEP in future.

• All potential variants of the transfer scheme will be considered, with varying levels of

assessment proportionate to the level of current and perceived future risk.

WFD: RBMP1 (2009) Status

Severn Thames Transfer Water quality and ecology assessment Phase 2

Waterbody ID Waterbody name Designation Overall status Overall ecological status Fish Inverts Plants Diatoms Ammonia DO pH Phosphate Temp Severn GB109054039760 River Severn – conf R Teme to conf R Avon Heavily Modified (Flood, Nav, Urban) Moderate Moderate High Poor High High High Poor High GB109054044404 River Severn – conf R Avon to conf Upper Parting Heavily Modified (Flood, Nav, Urban) Moderate Moderate Poor High High High Poor High Gloucester & Sharpness Canal GB70910509 Gloucester and Sharpness Canal Artificial (Nav) Moderate Moderate High High Moderate High Thames GB106039030170 Thames (Source to Kemble) Not Designated A/HMWB Good Good High High High High High GB106039023760 Thames (Kemble to Waterhay Bridge Not Designated A/HMWB Poor Poor Poor Good High High High High High GB106039022960 Thames (Waterhaybridge to Cricklade) and Chelworth Brook Not Designated A/HMWB Moderate Moderate Moderate High High High High High GB106039022990 Thames (Churn to Coln) Not Designated A/HMWB Poor Poor Moderate Good Poor High High High Moderate High GB106039023240 Thames (Coln to Leach) Heavily Modified (Nav) Moderate Moderate High GB106039029992 Thames (Leach to Evenlode) Not Designated A/HMWB Moderate Moderate Moderate Good High High High Moderate High GB106039030334 Thames (Evenlode to Thame) Not Designated A/HMWB Poor Poor Good Poor High High High Moderate High GB106039030331 Thames Wallingford to Caversham Heavily Modified (Flood, Navigation) Moderate Moderate Bad High High High Moderate High GB106039023233 Thames (Reading to Cookham) Heavily Modified (Flood, Nav, Water storage) Moderate Moderate High Good High High High Moderate High GB106039023231 Thames (Cookham to Egham) Heavily Modified (Flood, Nav, Water) Moderate Moderate High High High High High Moderate High GB106039023232 Thames (Egham to Teddington) Heavily Modified (Flood, Nav, Water) Poor Poor High Good Good Poor High High High Moderate High

WFD: RBMP1 (2009) Waterbodies - Status

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

WFD: RBMP2 (2014) Interim Status (not reported)

Severn Thames Transfer Water quality and ecology assessment Phase 2

Waterbody ID Waterbody name Designation Overall status Overall ecological status Fish Inverts Plants & Diatoms Ammonia DO pH Phosphate Temp Severn GB109054039760 River Severn – conf R Teme to conf R Avon Heavily Modified (Flood, Nav, Urban) Moderate Moderate Moderate High High High Poor High GB109054044404 River Severn – conf R Avon to conf Upper Parting Heavily Modified (Flood, Nav, Urban) Moderate Moderate Moderate Good High High High Poor High GB70910509 Gloucester and Sharpness Canal Artificial (Nav) Moderate Moderate High Good High Moderate High GB106039023760 Thames (Kemble to Waterhay Bridge Not Designated A/HMWB Moderate Moderate Good High Good High Moderate High High High GB106039022960 Thames (Waterhaybridge to Cricklade) and Chelworth Brook Not Designated A/HMWB Moderate Moderate High High Moderate High Moderate High Good High GB106039022990 Thames (Churn to Coln) Not Designated A/HMWB Moderate Moderate High High High Poor High GB106039029992 Coln (from Coln Rogers) and Thames (Coln to Leach) Not Designated A/HMWB Moderate Moderate High Moderate High High High Good High GB106039029992 Thames (Leach to Evenlode) Not Designated A/HMWB Poor Poor Poor Poor High High High Moderate High GB106039030334 Thames (Evenlode to Thame) Not Designated A/HMWB Moderate Moderate Moderate Moderate High High Poor Moderate High GB106039030331 Thames Wallingford to Caversham Heavily Modified (Flood, Navigation) Moderate Moderate Moderate High High High Poor High GB106039023233 Thames (Reading to Cookham) Heavily Modified (Flood, Nav, Water storage) Moderate Moderate High High High High Moderate High GB106039023231 Thames (Cookham to Egham) Heavily Modified (Flood, Nav, Water) Moderate Moderate High High High High Moderate High GB106039023232 Thames (Egham to Teddington) Heavily Modified (Flood, Nav, Water) Poor Poor Good Poor High High High Moderate High

WFD: RBMP2 (2014) Interim Status (not reported)

Severn Thames Transfer Water quality and ecology assessment Phase 2

Waterbody ID Waterbody name Designation Overall status Overall ecological status Fish Inverts Plants & Diatoms Ammonia DO pH Phosphate Temp Severn GB109054039760 River Severn – conf R Teme to conf R Avon Heavily Modified (Flood, Nav, Urban) Moderate Moderate Moderate High High High Poor High GB109054044404 River Severn – conf R Avon to conf Upper Parting Heavily Modified (Flood, Nav, Urban) Moderate Moderate Moderate Good High High High Poor High GB70910509 Gloucester and Sharpness Canal Artificial (Nav) Moderate Moderate High Good High Moderate High GB106039023760 Thames (Kemble to Waterhay Bridge Not Designated A/HMWB Moderate Moderate Good High Good High Moderate High High High GB106039022960 Thames (Waterhaybridge to Cricklade) and Chelworth Brook Not Designated A/HMWB Moderate Moderate High High Moderate High Moderate High Good High GB106039022990 Thames (Churn to Coln) Not Designated A/HMWB Moderate Moderate High High High Poor High GB106039029992 Coln (from Coln Rogers) and Thames (Coln to Leach) Not Designated A/HMWB Moderate Moderate High Moderate High High High Good High GB106039029992 Thames (Leach to Evenlode) Not Designated A/HMWB Poor Poor Poor Poor High High High Moderate High GB106039030334 Thames (Evenlode to Thame) Not Designated A/HMWB Moderate Moderate Moderate Moderate High High Poor Moderate High GB106039030331 Thames Wallingford to Caversham Heavily Modified (Flood, Navigation) Moderate Moderate Moderate High High High Poor High GB106039023233 Thames (Reading to Cookham) Heavily Modified (Flood, Nav, Water storage) Moderate Moderate High High High High Moderate High GB106039023231 Thames (Cookham to Egham) Heavily Modified (Flood, Nav, Water) Moderate Moderate High High High High Moderate High GB106039023232 Thames (Egham to Teddington) Heavily Modified (Flood, Nav, Water) Poor Poor Good Poor High High High Moderate High

WFD: RBMP2 (2014) Waterbodies – Interim status

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Baseline Ecological Descriptions and Risk Characterisation

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Requirements of Ecology Assessments

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Characterisation of ecological conditions in River Severn and River Thames.

Variant specific assessment of:

• Ecological consequence of when, how often and for how long transfer may
• perate.
• level of ecological sensitivity based on transfer triggers.
• What could River Severn flow and water quality change mean to ecology?
• What could River Thames flow and water quality change mean to ecology?

Severn Thames Transfer Water quality and ecology assessment Phase 2

Ecology - Fisheries

From policy to practice

Fish Assessment Methodology Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Preliminary risk characterisation exercise for each option considering aspects specific to current fish assemblage including:

• Rare and notable species
• Fish genetics (i.e. effects on genetically distinct populations of fish)
• Fish parasites/disease
• Invasive non-native species (INNS)
• Fish migration
• Habitats i.e. spawning and nursery habitat
• Eel regulations and Eel Management Plans
• WFD deterioration

Fish Assessment Methodology Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Baseline fish assemblage identified through:

• EA databases including:
• Juvenile fish monitoring programme,
• National Fisheries Monitoring Programme.
• TRaC fish survey programme.
• Hydroacoustic Programme
• Reference to the published literature
• Reference to Grey Literature including ‘Severn Thames Transfer: Water Quality

and Ecology Assessment - Phase 1: Initial Review, National Rivers Authority 1995’

Key River Severn Baseline Issues at Abstraction Locations Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Six protected fish species;
• European eel,
• river lamprey,
• sea lamprey,
• Atlantic salmon,
• brown/sea trout and
• twaite shad
• Possible remnants of allis shad population.
• Atlantic salmon populations of the Rivers Severn, Usk and Wye are genetically

unique.

• Twaite shad populations in Severn catchment also appear to show genetic

isolation.

Key River Severn Baseline Issues at Abstraction Locations Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• No fish pathogens unique to catchment identified.
• Species endemic to both Severn and Thames catchment.
• Isolated records of alien and non-native topmouth gudgeon Pseudorasbora

parva, currently subject of eradications measures by EA.

• Other invasive fish species present include zander and various sub-species of

carp Cyprinus carpio (common, mirror, koi, goldfish etc) all endemic to Thames catchment.

Potential Risk at River Thames Release Locations Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Similar assemblage and composition of fish stocks in River Thames and Severn.
• Both European eel and brown/sea trout, frequent the River Thames.
• Salmon are in decline despite recent salmon restocking programme.
• River and sea lamprey part of a panmictic north sea stock and migrate into the

lower River Thames in limited numbers in most years.

• Brook lamprey present in low numbers in the upper River Thames.
• Smelt are known to spawn in the Tideway above Wandsworth.
• River Thames grayling ‘are thought to be original, native populations and should be

protected from practices like stocking from other sources’

Potential Risks at River Thames Release Locations Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• River Thames and Thames Tideway host wide variety of INNS including:
• Chinese mitten crab
• Ruffe
• carp sub species including: common, mirror, koi, goldfish etc
• wels catfish
• Zander
• Pumpkinseed
• Rainbow trout

Potential Risks at River Thames Release Locations Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Impacts to river reaches at release locations are likely to come from direct change

to hydrological regime and water chemistry which may effect the composition of baseline fish stocks in terms of their ecological guilds.

• Impacts will generally be lower if discharge is made at more downstream release

locations.

Summary of Potential Key Issues Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Reduction in flow below River Severn abstraction points has the potential to:
• influence behaviour of migratory species,
• influence water chemistry
• modify fish habitats, and
• alter composition of fish stocks
• Requirement for appropriate intake screening to:
• reduce risk to protected species,
• reduce risk of transfer of INNS.
• Avoid deterioration of WFD ecological status (GES or GEP)

Risk must be assessed against future baseline based upon WFD obligations and predictions as well as likely climate change predictions and the potential resultant fish assemblage in the year 2030.

Severn Thames Transfer Water quality and ecology assessment Phase 2

Ecology – Invasive Species

From policy to practice

Invasive Species Assessment Methodology Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Focus placed on eight species:
• Quagga mussel, zebra mussel,

Asian clam, Caspian mudshrimp, demon shrimp, northern cangronyctid, signal crayfish, Nuttall’s waterweed

• Distributions identified through:
• EA databases
• Additional historical survey reports
• Focused field surveys in the upper Thames where data was lacking
• Key habitat requirements identified through:
• Reference to the published literature
• Species distribution models using habitat data from the Severn and

Thames

• Shifting baselines (especially important for invasives) identified through:
• Species distribution models to identify potential distributions under

current and 2050 climate scenarios

Key River Severn Invasive Species Baseline Issues at Abstraction Locations Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• River Severn contains a subset of the non-native species present in the

River Thames

• Gloucester-Sharpness Canal contains an especially high abundance of

zebra mussels and demon shrimps.

• Pipelines with sweetening flows very vulnerable to fouling by zebra mussels

and quagga mussels.

• Supporting reservoirs, if required, will create conditions that are especially

suitable to many non-native species, which would increase propagule pressure in subsequent transfers

Potential Invasive Species Key Issues at River Thames Release Locations Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Transfer would accelerate rate of invasion in Thames.
• The higher upstream the release location, the greater the overall impact will be

from invasive species introductions.

• Transfer from Severn of invaders already

found in Thames will introduce new genetic material into Thames.

• Zebra mussels and quagga mussels are

currently absent from Thames above Swinford.

• Without transfer, models predict quagga

mussels will invade into upper Thames (shifting baselines).

Summary of Invasive Species Potential Key Issues Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Supporting reservoirs will increase propagule pressure of non-native

species into the Thames.

• Pipelines with sweetening flows will be vulnerable to fouling by zebra and

quagga mussels and should be designed to include appropriate management systems.

• Transfer by canal is likely to facilitate the greatest introduction of non-native

species into the Thames

• Release points in more upstream locations is likely to result in the greatest

risk from invasive species in the Thames

Severn Thames Transfer Water quality and ecology assessment Phase 2

Ecology – Protected Species

From policy to practice

Protected Species Assessment Methodology Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Focus on freshwater mussels:
• Mussels are keystone organisms in large rivers
• Any changes to mussel populations will have ecosystem-level effects

and impact upon wider biodiversity

• Both the Severn and Thames support abundant mussel populations
• f duck mussel, painter’s mussel and depressed river mussel (a UK

BAP priority species)

• Distributions were identified through:
• EA databases
• Additional historical survey reports
• Focused field surveys in the upper Thames where data were lacking
• Key habitat requirements were identified through:
• Reference to the published literature
• Species distribution models using habitat data from the Severn and

Thames

Key River Severn Protected Species Baseline Issues at Abstraction Locations Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Abstraction, and subsequent changes in river flow, is unlikely to have a

marked risk on the river mussels, including the depressed river mussel.

• However, depressed river mussels typically occur in localised hotspots of

abundance which would be especially vulnerable to engineering works that affect the river bed through direct disturbance or siltation.

• A targeted survey for depressed river mussels is recommended in the

River Severn once the precise location and nature of the abstraction point has been identified.

Potential Protected Species Issues at River Thames Release Locations Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Risks are likely from i) direct change to habitat and ii) through the

introduction of invasive species.

• Risks will generally be lower if discharge is made at more downstream

release locations.

• Freshwater mussels are very rare upstream of Lechlade. Such patterns are

typical of upper river sections.

• Depressed river mussels are rarely found in the upper reaches of rivers. In

the Thames, the most upstream distribution point recorded is Buscot.

• Issues(whether positive or negative) must be assessed against forthcoming

models of hydrological change.

Summary of Protected Species Potential Key Issues Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• River mussels in the River Severn are unlikely to be impacted by

abstraction, although surveys should be conducted for depressed river mussels once the precise abstraction location has been identified.

• Depressed river mussels in the Thames are most abundant in the lower

reaches (Buscot and downstream). Key risks from release will be increased siltation (which can affect feeding, reproduction and substrate suitability) and increased abundance of fouling by zebra and quagga mussels.

• A more upstream release into the Thames will have a proportionately larger

effect on water quality and thus a greater potential impact on biodiversity in general.

View on Phase 1 findings from initial Phase 2 findings

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Ecological impacts on River Severn assessed to be low. 
• Moderate/high risk to Thames fish during a dry year.
• Moderate risk to Thames macroinvertebrates during dry year.
• Low/moderate risk to Thames ecology during average year.

Severn Thames Transfer Water quality and ecology assessment Phase 2

Next Steps

From policy to practice

Next Steps

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

• Agreement on reporting structure
• Completion of baseline reporting
• Agreement on Drinking Water Quality Assessment with other water companies
• Completion of WARMS2 runs with updated Severn flow record
• Production of scenario model runs for all scheme variants
• Progression of assessment topics with inclusion of scenario model runs
• Assessment reporting.

Discussion of Overall Reporting Structure

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Two Part Report

• Part A: Over-arching Assessment and Mitigation of Potential Risks
• Part B: Assessment and Mitigation of Potential Risks Each Transfer Scheme Variant
• 1 page NTS
• 3 page Executive Summary
• <100 page Main Report
• Technical detail provided in Technical Appendices
• Hydrology
• Water Quality Modelling
• Water Quality WFD
• Ecology: WFD/Fisheries/Protected Species/Invasive Species
• Drinking Water Quality

Severn Thames Transfer Water quality and ecology assessment Phase 2

A.O.B

From policy to practice

Severn Thames Transfer Water quality and ecology assessment Phase 2

Supporting Slides – not for presentation

From policy to practice

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Proposed sources and intake locations :

• River Severn at Deerhurst, to represent water quality of direct transfers by

pipeline – using data from Severn Trent Water’s nearby Mythe and Strensham intakes, and river quality data from the Environment Agency

• Gloucester Docks, mid Gloucester & Sharpness Canal and lower River

Frome, to represent water quality of direct transfers by canal – using data from Bristol Water’s monitoring programme

• River Thames at Farmoor Reservoir intake – using local data from Thames

Water

• River Thames at Datchet intake - using local data from Thames Water
• Other Water Companies intakes (i.e. South East Water or Affinity Water)

can be added if requested, and intake water quality data are provided).

WQ data analyses: tributyltin

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham No data available No data available No data available

WQ data analyses: dissolved chromium

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham No data available No data available

WQ data analyses: turbidity

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham No data available No data available No data available

WQ data analyses: alkalinity

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham

WQ data analyses: mercury

Severn Thames Transfer Water quality and ecology assessment Phase 2

From policy to practice

Severn Gloucester & Sharpness Canal Thames at Cricklade Thames at Lechlade Thames at Culham No data available No data available