Post on 15-Jul-2020
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 or 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 riskassessment
Drinking water safetyassessment
Water quality baselinecharacterisation
Hydrologycharacterisationand assessment
Water quality riskassessment
Future baselineFuture baseline
Drinking water safety baseline(Drinking Water Safety Plans)
Ecology baselinecharacterisation
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 on 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 operating 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 operate, 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 observed 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
ok
ok
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
operate.
• 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
of 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