Water Resources and Hydrogeology Framework (21981) Climate change and population growth modelling Environment Agency. 2 April 2014

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1 Water Resources and Hydrogeology Framework (21981) Climate change and population growth modelling Environment Agency 2 April 2014

2 Notice This document and its contents have been prepared and are intended solely for Environment Agency s information and use in relation identifying potential impacts from climate change and populations growth upon in stream phosphate concentrations in the Anglian region. Atkins assumes no responsibility to any other party in respect of or arising out of or in connection with this document and/or its contents. This document has 87 pages including the cover. Document history Job number: Document ref: Revision Purpose description Originated Checked Reviewed Authorised Date Rev 1.0 First draft JB JP KG PD 16/01/14 Rev 1.1 Revised draft JB JP PD PD 02/04/14 Client signoff Client Environment Agency Project Water Resources and Hydrogeology Framework (Contract No ) Document title Job no Copy no. Document reference Climate Change and Growth Modelling 001 Atkins Version April

3 Table of contents Chapter Pages Glossary of terms 7 Executive summary 8 1. Introduction Context Project background Scope of work Data Future Flows and Groundwater Levels Population Data Methodology SAGIS modelling Strategic dates Deriving change factors Growth Modelling Outputs provided Stakeholder workshop Assumptions and limitations Results Climate Change results Growth Ecological change Conclusions Climate change Growth Ecological Change Recommendations for further work References 35 Appendices 36 Appendix A. Growth projections for the Anglian region and the implication for increased sewage treatment works flow 37 A.1. References 37 Appendix B. Future Flow Data 41 B.1. Chater at Foster Bridge 41 B.2. Kym at Meagre Farm 42 B.3. Lark at Temple 43 B.4. Tove at Cappenham Bridge 44 B.5. Thet at Melford Bridge 45 B.6. Bedford Ouse at Offord 46 B.7. Rhee at Wimpole 47 B.8. Springside at Whitebridge 48 B.9. Thet at Bridgham 49 B.10. Stanford Water at Buckenham Tofts 50 B.11. Little Ouse at Knettishall 51 B.12. Tas at Shotesham 52 B.13. Waveney at Needham Mill 53 Atkins Version April

4 B.14. Wensum at Fakenham 54 B.15. Wensum at Swanton Morley 55 B.16. Stiffkey at Warham 56 B.17. Gipping at Stowmarket 57 B.18. Brett at Hadleigh 58 B.19. Belchamp Brook at Bardfield Bridge 59 B.20. Chelmer at Churchend 60 Appendix C. Climate Change River Reports 61 C.1. The River Brett 61 C.2. The River Waveney 63 C.3. Tas 66 C.4. Wensum 69 C.5. Wissey 72 C.6. Thet 75 C.7. Little Ouse 78 Appendix D. UKCP09 Comparison 82 Tables Table 2-1 Locations of flow gauges with Future Flows Hydrology data Table 4-1 Categories Table 4-2 Overall modelled impacts of predicted climate change upon the investigated areas of the Anglian region 23 Table 4-3 The current WFD water chemical status for soluble reactive phosphate Table 4-4 Baseline WFD status of water bodies in the Anglian region (expressed as number of water bodies and as a percentage of the total number of water bodies in the region of interest) Table 4-5 Growth scenario WFD status of water bodies in the Anglian region and percentage change relative to the baseline (expressed as number of water bodies and percentage of the total number of water bodies) 30 Table A-1 Dry Weather flow increase of STWs indentify the Entec report Table A-2 Growth projections and population increase from 2011 to 2031 and the implications for increased sewage effluent flow Figures Figure 3-1 The location of future flow gauges and the investigated reaches where change factors were available 14 Figure 4-1 Great Ouse Qmean Figure 4-2 Great Ouse Q Figure 4-3 Great Ouse Concentration Figure 4-4 Wensum Qmean Figure 4-5 Wensum Q Figure 4-6 Wensum concentration Figure 4-7 Modelled impact of predicted climate change upon Qmean Figure 4-8 Modelled impact of predicted climate change upon Q Figure 4-9 Modelled impact of predicted climate change upon phosphate concentration Figure 4-10 Baseline WFD status of water bodies against current and proposed EQS Figure 4-11 Growth modelled WFD status against current and proposed EQS Figure B-1 Chater Q change factors (as percent deviation from the baseline) Figure B-2 Chater Q95 change factors (as percent deviation from the baseline) Figure B-3 Kym Q change factors (as percent deviation from the baseline) Figure B-4 Kym Q95 change factors (as percent deviation from the baseline) Figure B-5 Lark Q change factors (as percent deviation from the baseline) Figure B-6 Lark Q95 change factors (as percent deviation from the baseline) Figure B-7 Tove Q change factors (as percent deviation from the baseline) Figure B-8 Tove Q95 change factors (as percent deviation from the baseline) Figure B-9 Thet Q change factors (as percent deviation from the baseline) Figure B-10 Thet Q95 change factors (as percent deviation from the baseline) Atkins Version April

5 Figure B-11 Bedford Ouse Q change factors (as percent deviation from the baseline) Figure B-12 Bedford Ouse Q95 change factors (as percent deviation from the baseline) Figure B-13 Rhee Q change factors (as percent deviation from the baseline) Figure B-14 Rhee Q95 change factors (as percent deviation from the baseline) Figure B-15 Springside Q change factors (as percent deviation from the baseline) Figure B-16 Springside Q95 change factors (as percent deviation from the baseline) Figure B-17 Thet Q change factors (as percent deviation from the baseline) Figure B-18 Thet Q95 change factors (as percent deviation from the baseline) Figure B-19 Stanford Water Q change factors (as percent deviation from the baseline) Figure B-20 Stanford Water Q95 change factors (as percent deviation from the baseline) Figure B-21 Little Ouse Q change factors (as percent deviation from the baseline) Figure B-22 Little Ouse Q95 change factors (as percent deviation from the baseline) Figure B-23 Little Ouse Q change factors (as percent deviation from the baseline) Figure B-24 Little Ouse Q95 change factors (as percent deviation from the baseline) Figure B-25 Waveney Q change factors (as percent deviation from the baseline) Figure B-26 Waveney Q95 change factors (as percent deviation from the baseline) Figure B-27 Wensum Q change factors (as percent deviation from the baseline) Figure B-28 Wensum Q95 change factors (as percent deviation from the baseline) Figure B-29 Wensum Q change factors (as percent deviation from the baseline) Figure B-30 Wensum Q95 change factors (as percent deviation from the baseline) Figure B-31 Stiffkey Q change factors (as percent deviation from the baseline) Figure B-32 Stiffkey Q95 change factors (as percent deviation from the baseline) Figure B-33 Gipping Q change factors (as percent deviation from the baseline) Figure B-34 Gipping Q95 change factors (as percent deviation from the baseline) Figure B-35 Brett Q change factors (as percent deviation from the baseline) Figure B-36 Brett Q95 change factors (as percent deviation from the baseline) Figure B-37 Belchamp Brook Q change factors (as percent deviation from the baseline) Figure B-38 Belchamp Brook Q95 change factors (as percent deviation from the baseline) Figure B-39 Belchamp Brook Q95 change factors (as percent deviation from the baseline) Figure B-40 Belchamp Brook Q95 change factors (as percent deviation from the baseline) Figure C-1 Brett Q Figure C-2 Brett Q Figure C-3 Brett phosphate concentration Figure C-4 Waveney Qmean Figure C-5 Waveney Q Figure C-6 Waveney phosphate concentration Figure C-7 Tas Qmean Figure C-8 Tas Q Figure C-9 Tas Phosphate concentration Figure C-10 Wensum Qmean Figure C-11 Wensum Q Figure C-12 Wensum phosphate concentration Figure C-13 Wissey Qmean Figure C-14 Wissey Q Figure C-15 Wissey phosphate concentration Figure C-16 Thet Qmean Figure C-17 Thet Q Figure C-18 Thet phosphate concentration Figure C-19 Little Ouse Qmean Figure C-20 Little Ouse Q Figure C-21 Little Ouse phosphate concentration Figure D-1 UKCP09 and Future Flows Comparison of Annual Change Factors for Kym at Meagre Farm (Medium emissions for the 2050s) Figure D-2 UKCP09 and Future Flows Comparison of Annual Change Factors for Stringside at Whitebridge (Medium emissions for the 2050s) Figure D-3 UKCP09 and Future Flows Comparison of Annual Change Factors for Waveney at Needham Mill (Medium emissions for the 2050s) Figure D-4 UKCP09 and Future Flows Comparison of January Change Factors for Waveney at Needham Mill (Medium emissions for the 2050s) Figure D-5 UKCP09 and Future Flows Comparison of January Change Factors for Kym at Meagre Farm (Medium emissions for the 2050s) Atkins Version April

6 Figure D-6 UKCP09 and Future Flows Comparison of January Change Factors for Kym at Meagre Farm (High emissions for the 2050s) Figure D-7 UKCP09 and Future Flows Comparison of June Change Factors for Kym at Meagre Farm (Medium emissions for the 2050s) Figure D-8 UKCP09 and Future Flows Comparison of June Change Factors for Kym at Meagre Farm (High emissions for the 2050s) Atkins Version April

7 Glossary of terms Terms Compliant/compliance Meaning / Definition Achieving good or high WFD status Current EQS The current WFD EQS for PO 4 (Table 4-3)Table 4-3 EQS FFGWL Environmental quality standard Future Flows and Groundwater Levels Future EQS The proposed WFD EQS for PO 4 (Atkins 2013c) HadRM3 ILC INCA IPCC PPE Q95 Qmean SAGIS SIMCAT SRES STW Hadley Centre Regional Climate Model Integrated Lake and Catchment model Dynamic model representation of plant/soil system dynamics and in-stream biogeochemical and hydrological dynamics (developed by Reading University) Intergovernmental Panel on Climate Change Perturbed Physics Ensemble 95 th percentile flow Mean flow Source Apportionment Geographical Information System (incorporating an upgraded version of SIMCAT) A multi-reach catchment water quality model developed by the Environment Agency Special Report on Emissions Scenarios Sewage treatment works UKCP09 United Kingdom Climate Projections 2009 WB WFD Waterbody Water framework directive Atkins Version April

8 Executive summary This report details modelling studies that were carried out as part of the Water Resources and Hydrogeology Framework (21981). This work extends the work initiated in Atkins (2013a,b,c,d) and uses the Future Flows Hydrology dataset (Haxton et al., 2012) to generate change factors for modelling the impact of climate change on in-stream phosphate concentrations. The aim of this project is to use Future Flows and the latest population growth projections (Environment Agency, 2013) to identify their implications on phosphate concentrations, legislative compliance and ecological change. In order to assess potential combined impacts of climate change and population growth upon phosphate concentrations in the rivers of the Anglian region, the calibrated and validated SAGIS model produced for the Anglian region Environment Agency was used. Monthly climate change factors were applied to SAGIS at locations where future flow data was available and to reaches upstream of these points. Baseline and future periods were selected as and (2050s) respectively. To assess the impact of population growth upon phosphate concentrations in the rivers of the Anglian region, data provided by the Anglian region Environment Agency was used. This comprised predicted population increases per local authority area for These population increases were converted to their estimated additional contributions as to flow to works which was then divided across the large sewage treatment works (STWs) in the relevant local authority area. As a result of climate change, overall, Qmean and Q95 values are predicted to decrease for the future condition compared to baseline values. However, predictions of Qmean for the Little Ouse and Q95 for the Brett are both uncertain: such that both Qmean and Q95 could increase or decrease. For the Brett, Waveney and Tas, predictions suggest lower phosphate concentrations despite reduced Qmean and Q95. This is likely due to the loss of velocity in these rivers. For most other rivers including the Great River Ouse and the Wensum, an increase in phosphate concentration is predicted. In terms of the modelled impact of population growth, 5% of waterbodies classified as high or good across the region are downgraded to less than good status. The greatest impact of population growth is shown to be an overall increase in poor status waterbodies. Waterbodies classified as high, good or moderate are shown to decrease in abundance. North West Norfolk, North Norfolk and the Broadland Rivers management catchments appear to be the most resilient to reduced water quality as a result of population growth. However, the Cam and Ely Ouse, Upper Bedford Ouse, Nene, Welland and Witham catchments appear to be less resilient. The deterioration in phosphate concentrations indicated by the analysis of climate change and population growth suggests that the ecological status would deteriorate but this is constrained by other influences on the biological community. Climate change will affect other influences on the biological community including water temperature and flow velocity and for many rivers this is likely to be as important as changes in phosphate concentrations. Reduced river flows in particular are likely to have a harmful impact on the biology and this may well be more important than changes in phosphate concentrations. Atkins Version April

9 1. Introduction 1.1 Context Freshwater eutrophication is a significant issue nationally with 45% of river water bodies assessed for phosphorus in England failing the current WFD phosphate standard. In the Anglian region 51% (380 out of 790) water bodies are failing the WFD phosphate standard (Atkins 2013d). In the Anglian region phosphate is the second most common reason for failure after mitigation measure assessments. The Anglian region was selected to contribute to strategic thinking on phosphate due to the significance of the problem in the region but also due to the long term experience of tackling phosphate pollution. Climate change driven increases in river and lake temperatures and reduced flows are expected to exacerbate the symptoms of eutrophication such as algal growth (Whitehead et al., 2012). The Anglian region is also a growth area, with population growth already taking place. This is likely to cause further degradation in phosphate water quality due to increased loads from sewage treatment works (STWs) and more intensive farming practices in order to feed a growing population. Therefore effective planning of water quality improvements need to be designed to be able to deal with future challenges as well as those apparent now. The success of water quality improvement measures will depend not only on their effectiveness but their longevity in addressing water quality. 1.2 Project background In 2013 Atkins successfully delivered a series of Source Apportionment GIS (SAGIS) modelling studies which investigated catchments within the Anglian Region for the Environment Agency. The modelling work was carried out as part of the Water Resources and Hydrogeology Framework (21981). Initially in April 2013 Atkins was appointed by the Environment Agency to better understand the merits and weaknesses of a number of catchment scale river quality models developed in recent years to support river basin planning; notably SAGIS (incorporating an upgraded version of SIMCAT), the Integrated Lake and Catchment model (ILC) and INCA (Atkins, 2013a). The aim was to identify any development needs for SAGIS (e.g. by adding functionality present in INCA and ILC). In June 2013 the Environment Agency commissioned Atkins to identify three catchments (selected from within the 100 Defra river catchments) suitable to investigate a range of pressures and measures related to phosphate contamination (Atkins, 2013b). Following a ranking exercise based on the relative density of sewage treatment works (STWs), livestock and surface water abstractions, three catchments were identified for packages of potential phosphate reduction options. These were: Upper and Bedford Ouse, Cam and Ely Ouse, and Stour. Consequently, Atkins investigated the impact of a suite of measures upon present and future baselines in these catchments. Further work (Atkins, 2013c) investigated targeting the most cost effective measures to achieve phosphorus EQS compliance in three pilot catchments identified in Atkins (2013b) and a further catchment identified by the Environment Agency (River Ant). These measures included those targeted at STWs, livestock and arable farming runoff, urban diffuse pollution, industrial effluent and septic tanks. In this work SAGIS modelling was used to investigate the impact of chosen measures upon present and future baselines for the four catchments (Upper and Bedford Ouse, Cam and Ely Ouse, Stour, and Ant). The next report (Atkins, 2013d) extended this work (Atkins, 2013c) and delivered a scenario analysis of potential options for reducing phosphate in all thirteen management catchments within the Anglian region. The effectiveness of all measures (as in Atkins, 2013c) was tested against the current and future proposed Environment Quality Standard (EQS) for soluble reactive phosphate as required under the current Water Framework Directive (WFD) regulations. Using this information, a computational proof of concept model was developed to demonstrate how targeting might be addressed mathematically with a view to adopting this approach in future similar assessments. This report presented data that indicated what improvements in water quality can be made for the investment budgets of 100,000, 1,000,000 and 10,000,000. This project also summarised the expected ecological consequence of water quality resulting from the investigated scenarios. Atkins Version April

10 1.3 Scope of work This work extends the work initiated in Atkins (2013c) and Atkins (2013d) and uses the Future Flows Hydrology dataset to generate change factors for modelling the impact of climate change on in-stream phosphate concentrations. The impact of population growth upon water quality in the region is assessed in greater detail than previous reports. The aim of this project is to use the Future Flows dataset and the latest population growth projections to identify the impacts of climate change and population growth on phosphate concentrations, legislative compliance and ecological changes. A suite of possible future scenarios will be tested and their impacts considered against a baseline period. In the proposal from Atkins to the Environment Agency entitled Climate Change and Growth Modelling the following overall objectives were agreed: 1. Identify strategic dates for which climate change and population growth estimates can be assessed against. 2. Identify baseline and future measures scenarios to test climate change and population growth estimates against (based on modelling work completed under the packages of measures and Anglian P modelling support projects; Atkins, 2013c). 3. Use the Future Flows dataset to derive change factors for a future climate in the 2050s, to be used to perturb the input values for Q mean and Q Use the latest projections for population growth to model the situation for phosphate at set future dates. 5. Summarise expected ecological improvements as a result of changes. 6. Produce a SAGIS dataset including climate change and growth projections, to use in planning, will be provided. 7. Outputs will be in the form of a report, data summaries and visual aids for stakeholder engagement. 8. Present findings as part of a stakeholder workshop. Atkins Version April

11 2. Data 2.1 Future Flows and Groundwater Levels The Future Flow Hydrology dataset (Haxton et al., 2012) provides the climate change impact information for this study. The Future Flows and Groundwater Levels (FFGWL) project was commissioned in order to provide a consistent assessment of climate change impact for river flows and groundwater levels across Great Britain (Prudhomme et al., 2012a). FFGWL is made up of two principal datasets (ibid): 1. Future Flows Climate (Prudhomme et al., 2012b) is an 11-member ensemble 1-km gridded projection time-series ( ) of precipitation and potential evapotranspiration for Great Britain specifically developed for hydrological application. It is based on the 11-member Perturbed Physics Ensemble (PPE) 1 of the Hadley Centre Regional Climate Model (HadRM3), run under the Medium emissions scenario (A1B of SRES 2 ). 2. Future Flows Hydrology (Haxton et al., 2012) is an 11-member ensemble projection of 148 years ( ) of transient daily river flow and monthly groundwater level time-series for 281 river catchments and 24 boreholes in Great Britain using Future Flows Climate as forcing data. Of the 281 river catchments Future Flows Hydrology provides data for, 20 were in the Anglian region and therefore these were used in the assessment (see Table 2-1). Table 2-1 Locations of flow gauges with Future Flows Hydrology data River Gauge Number Name NGR Kym Kym at Meagre Farm TL Tove Tove at Cappenham Bridge SP Bedford Bedford Ouse at Offord TL Chater Chater at Fosters Bridge SK Brett Brett at Hadleigh TM Belchamp Brook Belchamp Brook at Bardfield Bridge TL Chelmer Chelmer at Churchend TL Lark Lark at Temple TL Thet Thet at Melford Bridge TL Rhee Rhee at Wimpole TL Stringside Stringside at Whitebridge TF Thet Thet at Bridgham TL Stanford Stanford Water at Buckenham Tofts TL Little Little Ouse at Knettishall TL Tas Tas at Shotesham TM Waveney Waveney at Needham Mill TM Wensum Wensum at Fakenham TF Wensum Wensum at Swanton Morley Total TG Stiffkey Stiffkey at Warham All Saints TF Gipping Gipping at Stowmarket TM A perturbed physics ensemble (PPE) is an ensemble of model runs from different model variants, produced by varying the values of parameters in a given climate model configuration (UKCP09, 2012). 2 Special Report on Emissions Scenarios by the Intergovernmental Panel on Climate Change (IPCC). See Nakićenović et al. (2000) for more details on the scenarios. Atkins Version April

12 There are two principal limitations of the Future Flows Hydrology data; firstly, the database is only based on the ensemble within HadRM3 and therefore does not include uncertainty from other climate models; and secondly, the data were only produced for the Medium emissions scenario and so do not encompass the full range in the projections from the Low (B1 from SRES) and High (A2 from SRES) scenarios. These limitations are explored in more detail in Section Population Data The Anglian regional Agency Priority places report, (Environment Agency, 2013) give projections for population growth increases per local authority up to the year These population increases form the basis for predictions of how population change could influence water quality. The limitations are that this is a predicted population increase; it has been necessary to convert these population increases into additional flow to works using generalised formulae (Appendix A). The Impacts of Growth on Water Quality in the East Anglian: Assessment to Support the RSS Review (Entec 2010) identifies specific STWs that are likely to be impacted by population growth. Data was available in the form of increases in flow to works. Where available, this data was used in preference over the population increase data. Atkins Version April

13 3. Methodology The approach and methodology of this study were agreed at a project inception meeting between Atkins and the Environment Agency. 3.1 SAGIS modelling The calibrated and validated SAGIS models produced for the Anglian regional Environment Agency were used to assess potential impacts on phosphate concentrations in Anglian rivers (Atkins, 2013a). 3.2 Strategic dates As the Future Flows Hydrology dataset provides transient timeseries, users have the flexibility to choose any period(s) around which to generate change factors. Periods should be at least 30-years in length. 30 years is typically the minimum length of time to consider climate changes as this length of period will smooth out the variability in climate from one year to the next. Using fewer years could result in the baseline being skewed by unusually warm, cold, wet or dry years within that period. By way of example, UKCP09 provides climate change projections for seven overlapping timeslices (30-year periods), each centred on a particular decade (e.g. the 2020s covers , the 2030s covers , etc). These projections were generated against a baseline period of is often used as a baseline for climate change projections; however, more recent baselines are often used for example, the latest Intergovernmental Panel on Climate Change (IPCC) Assessment Report ( AR5 ) uses a baseline for its projections. In selecting an appropriate baseline period there are a number of considerations. Firstly, the baseline for the SAGIS model is If, for example, a baseline period were selected for the climate change factors, this would result in a potential overestimation of the impact of climate change. This is because the factors would be calculated against a period with a smaller climate signal than the period that the factors are subsequently applied to. Secondly, this study also considers the changes in population in parallel with the climate. The population growth projections provided by the Environment Agency are for the future period against a baseline of It is therefore also desirable to maintain consistency between the climate and population changes. A baseline period of was selected for this study as this was consistent with the population growth data and also covered the same period as the SAGIS model (though it is longer). As a check, a comparison with climate change factors against a baseline of was carried out for three locations: the Thet at Melford Bridge, Stiffkey at Warham and Chelmer at Churchend (giving a spread across the Anglian Region). This comparison showed average monthly differences in the two sets of change factors for mean flow of - 0.7%, 0.0% and 0.6% respectively. It was therefore decided that using a baseline of would not be substantially different from using the period that exactly matched the SAGIS baseline. In summary, the baseline and future periods for the study were selected as and respectively. These time periods correspond with the dates of the population projections provided by the Environment Agency. 3.3 Deriving change factors The flow inputs to the SAGIS model are monthly values of Qmean and Q95. Therefore, modelling the impact of climate change in SAGIS requires perturbing those flow input values. The transient data from the Future Flows Hydrology dataset is used to generate monthly change factors to use in the perturbation. Deriving the change factors requires two straightforward steps: 1. Calculate Qmean and Q95 for each of the 11 members of the ensemble for baseline ( ) and future periods ( ), on a monthly basis. 2. Divide the resulting future figures by their corresponding baseline to derive change factors. Atkins Version April

14 The output of the above process is a set of 11 monthly change factors. The advantage of using monthly factors over annual is that monthly factors will reveal intra-annual impacts of climate change, for example, reductions in summer flows are potentially offset by winter increases Applying climate change factors Monthly change factors were applied to SAGIS at locations where Future Flow data were available and to reaches upstream of these points (Figure 3-1). Where two or more flow gauges were located on the same reach, change factors were applied from the downstream gauge upstream. The change factors from the downstream gauge were applied up to the reach where the upstream gauge was located. From here on, change factors associated with the next flow gauge were applied. Figure 3-1 The location of future flow gauges and the investigated reaches where change factors were available Atkins Version April

15 Assessment of the impact of climate change Changes in Qmean, Q95 and phosphate concentration as a result of climate change were all assessed by comparison of the individual future scenario modelled outputs with the present baseline Investigated rivers The investigated rivers of the region were categorised based upon the number of future scenario modelled outputs that predicted higher or lower Qmean, Q95 and phosphate concentrations. The following methodology was used for Qmean, Q95 and phosphate concentration individually: Each investigated river was assessed at 10 Km from the source to the downstream limit of investigation. If 8 out 11 ensembles are greater than the baseline for 60 % of the river then it is classified as higher than the baseline. If 4 out 11 ensembles are lower than the baseline for 60 % of the river then it is classified as lower than the baseline. If 5 and 7 for 80 % of the river or does not fit into the previous two criteria, then the river is classified as uncertain The Anglian region The Anglian region was categorised based upon the number of future scenario modelled outputs that predicted higher or lower Qmean, Q95 and phosphate concentrations in the future. This was then mapped to provide a broad outline of the implications of climate change upon the region. The following methodology was used for Qmean, Q95 and concentration individually: Each of the SAGIS outputs along the reaches that had future flow data available were assessed within each of the waterbodies that had change factors applied (Figure 3-1). If 8 out of 11 ensembles are greater than the baseline for 60 % of the river then it is classified as higher than the baseline. If 4 out of 11 ensembles are lower than the baseline for 60 % of the river then it is classified as lower than the baseline. If 5 and 7 for 80 % of the river or does not fit into the previous two criteria, then the river is classified as uncertain. The waterbody was classified as higher if 60 % of the SAGIS outputs within that waterbody were higher. The waterbody was classified as lower if 60 % of the SAGIS outputs within that waterbody were lower. Any waterbody not fulfilling the criteria for higher or lower was classified as uncertain. 3.4 Growth Modelling To assess the impact of population growth upon phosphate concentrations in the rivers of the Anglian region, data provided by the Anglian region Environment Agency was used (EA Anglian priority places, internal source). This comprised predicted population increases per local authority area for These increases were converted to flow (Appendix A) which was then divided across the large STWs in the local authority area. 3.5 Outputs provided Outputs are in the form of a report, data summaries and visual aids for stakeholder engagement. Atkins Version April

16 A SAGIS dataset including climate change and growth projections to use in planning are provided in Section Appendix Band in Appendix C. 3.6 Stakeholder workshop Outputs from this study were presented at an Environment Agency workshop on Phosphorus and Eutrophication which was held on the 13 th November 2013 and feedback was received from a range of stakeholders. 3.7 Assumptions and limitations There are several limitations of the data and approach of this study that should be noted. These include: Future Flows is based on an 11 member ensemble so does not explore the range of model uncertainty captured by the UKCP09 probabilistic climate projections. Future Flows is only based on the ensemble within HadRM3 and therefore does not include uncertainty from other climate models. Future Flows was only produced for the Medium emissions scenario and so does not encompass the full range of projections from the Low and High scenarios. Therefore, the worst-case scenario used here is not necessarily the largest possible reduction in flows. A comparison between Future Flows and the full range of the UKCP09 can be found in Appendix D The individual Future Flows Hydrology datasets have been produced by different regionalised models. Though they have all been calibrated with the same Met Office Rainfall and Evaporation Calculation System (MORECS) monthly potential evapotranspiration dataset, each model will have its own uncertainties and biases. This should be considered when making direct comparisons between locations. The study uses a 42-year baseline rather than the standard 30 years as used in most studies. The implications of this have been discussed in Section 3.2. Atkins Version April

17 Q (Ml/d) 4. Results 4.1 Climate Change results This section summarises the key findings of this investigation in relation to the potential impacts of climate change upon the concentration of phosphate in the rivers of the Anglian region. Below in Sections and 4.1.2, the impacts of climate change on the two longest investigated rivers are explored. The other large rivers of the region are shown in Appendix C. A summary of all investigated rivers in the region is presented in Section The Great River Ouse The Great River Ouse is the longest river investigated (circa 158 Km from the source to the downstream limit of investigation). The impact of the eleven future flow ensembles on the Qmean and Q95 in the Great River Ouse are shown in Figure 4-1 and Figure 4-2. The range of Qmean and Q95 values either side of the baseline demonstrate uncertainty in the future flow projections Qmean The majority of future flow predictions suggest a decrease in annual flow compared to the baseline flow between the source and 133km downstream. From this point to the downstream limit predictions become less certain. At the river midpoint (80 Km from the source) the baseline Qmean is 955 ML/d, whereas the projected range from the future flow ensembles is 593 to 1007 ML/d (Figure 4-1). At this midpoint, eight of the eleven ensembles predict lower mean flow. At the downstream limit (41 Km from the source) the baseline Q is 252 ML/d, whereas the projected range from the future flow ensembles is153 to 261 ML/d (Figure 4-1). At the downstream limit, four of the eleven ensembles predict lower mean flow Baseline flow Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q Figure Distance (KM) Great Ouse Qmean Atkins Version April

18 Q (Ml/d) Q95 Results suggest that the majority of the future flow predictions produce lower Q95 in comparison to the baseline. At the river midpoint (80 Km from the source) the baseline Q95 is 179 ML/d, whereas the projected range from the future flow ensembles is 124 to 165 ML/d (Figure 4-2). At this midpoint, all eleven of the ensembles predict lower Q95. At the downstream limit (158 Km from the source) the baseline Q95 is 167 ML/d, whereas the projected range from the future flow ensembles is 167 to 167 ML/d (Figure 4-2). At the downstream limit, all Q95 values for the baseline and the ensemble are similar. This is a result of the major abstraction at Offord that occurs at this location Baseline Q95 Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q Figure Distance (KM) Great Ouse Q Phosphate concentration Over the entire 158 Km length investigated, an increase in annual average PO 4 concentration compared to the baseline is observed in response to the majority of predicted future flows tested (Figure 4-3). Under the future conditions tested this river does not demonstrate a significant drop in velocity that could indicate removal of PO 4 through settlement. At the river midpoint (80 Km from the source) the baseline concentration is 0.26 mg/l, whereas the projected range from the future flow ensembles is 0.28 to 0.41 mg/l (Figure 4-3). At this midpoint, all of the eleven ensembles predict higher concentrations. At the downstream limit (158 Km from the source) the baseline concentration is 0.21 mg/l, whereas the projected range from the future flow ensembles is 0.19 to 0.28 mg/l (Figure 4-3). At this downstream limit, nine of the eleven ensembles predict higher concentrations. Atkins Version April

19 PO4 Concentration (mg/l) Baseline annual mean Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q9 0.0 Figure Distance (KM) Great Ouse Concentration Wensum Implications of Qmean and Q95 upon the Wensum based upon the climate projections of the eleven future flow ensembles are shown in Figure 4-4 and Figure 4-5. The range of predicted Qmean and Q95 values either side of the baseline demonstrate the uncertainty in future flow projections. Furthermore, as stated previously, the Future Flows predictions are based on a subset of the full range of model uncertainty captured by the UKCP09 projections Qmean It is observed that the majority of future flow ensembles tested produce lower annual flow in comparison to the baseline. At the river midpoint (21 Km from the source) the baseline Qmean is 128 ML/d, whereas the projected range from the future flow ensembles is 63 to 106 ML/d (Figure C-10). At this midpoint, all eleven ensembles predict lower mean flow. At the downstream limit (41 Km from the source) the baseline Qmean is 252 ML/d, whereas the projected range from the future flow ensembles is 153 to 261 ML/d (Figure 4-4). At the downstream limit, nine of the eleven ensembles predicted lower mean flow. Atkins Version April

20 Q (Ml/d) Baseline flow Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q Figure Distance (KM) Wensum Qmean Q95 It is observed that the majority of the future flow ensembles produce lower Q95 in comparison to the baseline. At the river midpoint (21 Km from the source) the baseline Q95 is 23 ML/d, whereas the projected range from the future flow ensembles is 9 to 18 ML/d (Figure C-11). At this midpoint, all eleven of the ensembles predict lower Q95 flow. At the downstream limit (41 Km from the source) the baseline Q95 is 252 ML/d, whereas the projected range from the future flow ensembles is 42 to 25 ML/d (Figure 4-5). At the downstream limit, eight of the eleven ensembles predict lower mean flow. Atkins Version April

21 Q (Ml/d) Baseline Q95 Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q9 0 Figure Distance (KM) Wensum Q Phosphate concentration Up to 25 km downstream from the source, an increase in annual average phosphate concentration compared to the baseline is modelled for every ensemble (Figure 4-6). From this point up to 32 Km from the source the majority of future flow ensembles predict higher concentrations of phosphate in comparison to the baseline. From this point downstream, the majority of the flow ensembles predict lower concentrations. This could be due to the lower velocities that would result from lower Q. Within SIMCAT velocity has a direct relationship with settling rate. Thus in the case of the Wensum, lower velocities could result in greater settlement of phosphate and removal from the water column at the lower reaches. At the river midpoint (21 Km from the source) the baseline concentration is 0.09 mg/l, whereas the projected range from the future flow ensembles is 0.10 to 0.17 mg/l (Figure C-12). At this midpoint, all of the eleven ensembles predict higher concentrations. At the downstream limit (41 Km from the source) the baseline concentration is 0.16 mg/l, whereas the projected range from the future flow ensembles is 0.10 to 0.18 mg/l (Figure 4-6). At this downstream limit, only one of the eleven ensembles predict higher concentrations Atkins Version April

22 PO4 Concentration (mg/l) Baseline annual mean Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q9 0.0 Figure Distance (KM) Wensum concentration Summary of climate change and its impact on phosphate concentrations in the region Impact of climate change on the investigated rivers Based on the assessment criteria detailed in Section 3.3.2, the rivers investigated all fall into one of four categories (Table 4-1). Overall, Qmean and Q95 values are predicted to decrease from the baseline values. However, the predictions for Qmean for the Little Ouse and Q95 for the Brett were both uncertain: meaning both Qmean and Q95 could increase or decrease. Despite reduced Qmean and Q95 from the baseline values, category one and two predict lower phosphate concentrations, this is the case for the Brett, Waveney and Tas. The reason for this is likely due to the loss of velocity that occurs with reduction in flow. This would result in increased sedimentation and a loss of phosphate through this means. However, although phosphate concentrations may be lower in the future, lower flows could result in depressed ecological status. In category three and four (the largest proportion of rivers) an increase in phosphate concentration is predicted. Table 4-1 Categories Category River Qmean Q95 Concentration One Brett Lower Uncertain Lower Two Waveney Lower Lower Lower Tas Lower Lower Lower Three Wensum Lower Lower Higher Great River Ouse Lower Lower Higher Wissey Lower Lower Higher Thet Lower Lower Higher Four Little Ouse Uncertain Lower Higher Atkins Version April

23 Impact of climate change on the Anglian region This is in agreement with a wider analysis undertaken on all the reaches covered by the future flow gauge locations (Figure 3-1). The overall impacts of climate change upon Qmean, Q95 and concentration are shown in Figure 4-7, Figure 4-8 and Figure 4-9 respectively. Qmean Of the area where future flows data was available, 50% of the waterbodies are likely to have reduced flow. Interestingly, there appears to be areas where flow may well increase, particularly the Chater and the Waveney. This is likely due to the increased winter flow predicted by the future flow data sets (Appendix A). The modelled results indicate an uncertain estimation, as 29% of the waterbodies had flow that had been predicted to both increase and decrease. Q95 It is modelled that the majority of waterbodies (83%) are predicted to have lower Q95. This indicates the potential for a greater frequency of droughts in the Anglian region. Phosphate concentration Model results suggest increased phosphate concentrations in the majority of waterbodies investigated. Interestingly, 16% of the waterbodies predict lower phosphate concentrations. These areas do not necessarily coincide with areas where high flow is predicted. In fact these locations predominantly coincide with areas of lower Qmean and Q95. As such, these areas would suffer from lower in stream velocities, and increased sedimentation. This would lead to a removal of phosphate via this route. Although concentrations of phosphate may be less, siltation and reduction in ecological quality as a result may be a serious issue in the future. Future in stream phosphate concentration is dependent upon loads from point and diffuse source, the dilution capacity of receiving waters and the degradation rate of phosphate. An important mechanism for the removal of phosphate is via sedimentation which is dependent upon velocity. These results may indicate that phosphate concentration is likely to increase in the majority of waterbodies. However lower future phosphate estimated concentrations could indicate that below a threshold flow, sedimentation due to the velocity could cause a river to exhibit net removal of phosphate. The SAGIS model represents phosphate removal predominantly by sedimentation. It has not been possible to assess how phosphate removal would be impacted by biotic changes as a result of climate change. Table 4-2 Overall modelled impacts of predicted climate change upon the investigated areas of the Anglian region Category Qmean Q95 Concentration High 21% 3% 58% Uncertain 29% 14% 27% Lower 50% 83% 16% Atkins Version April

24 Figure 4-7 Modelled impact of predicted climate change upon Qmean Atkins Version April

25 Figure 4-8 Modelled impact of predicted climate change upon Q95 Atkins Version April

26 Figure 4-9 Modelled impact of predicted climate change upon phosphate concentration Atkins Version April

27 4.1 Growth This section presents the key findings of the impact assessment of population growth on the phosphate concentrations and corresponding WFD status in the rivers of the Anglian region. The growth scenario was developed based on population growth data provided by the Anglian region Environment Agency (EA Anglian priority place, internal source). These data comprised predicted population increases per local authority area for These population increases were converted to flow increases across the large STWs of the local authority area (see Atkins, 2013b). The WFD status of each water body was calculated using methodology authorised by the National Environment Agency (Atkins, 2013c). The concentration of the downstream water body boundary point was used to define the water body WFD compliance status. The criteria for current soluble reactive phosphate (SRP) standards are given in Table 4-3. Table 4-3 The current WFD water chemical status for soluble reactive phosphate Soluble reactive phosphate concentration in mg/l < 0.05 High < 0.12 Good WFD status < 0.25 Moderate < 1 Poor > 1 Bad The WFD status of water bodies in the catchment is assessed in terms of the current EQS. In addition to this, the results of the scenario modelling are also assessed using the proposed SRP EQS (referred to henceforth as future EQS). These new standards take into account the influence of river typology to determine the WFD status. Lists of the proposed water body specific standards are provided in Atkins (2013b) Baseline The baseline WFD status, using both current and future EQS as benchmarks, is listed in Table 4-4. The present baseline indicates that over 74% of water bodies fail to comply with the current EQS for phosphate to achieve good status. This would be further exacerbated if the future EQS were applied as 82% of water bodies would fail the standard. The Upper Bedford Ouse catchment has a slightly higher proportion of water bodies that do not comply; only 12% of water bodies are compliant when assessed against current EQS and only 7% compliant if they are assessed against the proposed EQS. Relative to the catchment as a whole this corresponds to 1.2%.The water quality status in the catchment of the Cam and Ely Ouse is comparatively better, with over 20% of water bodies in this part of the region having better than good status (or 3.3% over the entire region). Table 4-4 Baseline WFD status of water bodies in the Anglian region (expressed as number of water bodies and as a percentage of the total number of water bodies in the region of interest) WFD Status Current EQS Future EQS Entire catchment High 55 (8%) 55 (8%) Good 133 (18%) 75 (10%) Moderate 242 (33%) 241 (33%) Poor 274 (37%) 334 (46%) Bad 28 (4%) 27 (4%) Upper and Bedford Ouse High 1 (1%) 1 (1%) Good 10 (11%) 5 (6%) Moderate 32 (36%) 30 (34%) Poor 44 (49%) 52 (58%) Atkins Version April

28 WFD Status Current EQS Future EQS Bad 2 (2%) 1 (1%) Cam and Ely Ouse High 7 (8%) 7 (8%) Good 17 (17%) 10 (12%) Moderate 40 (47%) 40 (47%) Poor 22 (26%) 29 (34%) Bad 0 0 The mapped WFD status using both current and future EQS as benchmarks are presented in Figure Atkins Version April

29 Figure 4-10 Baseline WFD status of water bodies against current and proposed EQS Atkins Version April

30 Growth scenario The results of the growth modelled WFD status against both current and future EQS are given in Table 4-5 and Figure Comparison of the results with the baseline shows that population growth as predicted in the Anglian region may cause significant deterioration in WFD status in the catchment. When assessed against the current standard, 74% of water bodies fail at present, whereas population growth would increase the number of failing water bodies to 79%. Using the future EQS shows the same impact. While only one or two water bodies deteriorate from High status, the biggest impact is seen in the Good and the Moderate status (4% and 10% change respectively). The modelled impact of population growth on the Upper Bedford Ouse is small relative to the entire catchment. In this area 1% of water bodies would become less than Good when assessed against the current EQS; this corresponds to a less than 1% change over the entire catchment. In the categories of lower water quality, the biggest change occurs in the water bodies that currently have Moderate status; close to 10% of these water bodies would deteriorate to Bad status. The modelled impact on the Cam and Ely Ouse on the other hand is larger and may be the more important contributor to the overall deterioration of water quality status in the catchment as a whole. The assessment shows no change in status in the highest category, but over 10% of water bodies that currently have Good status deteriorate. This corresponds to a 1.5% change over the entire region. Again, the biggest impact is seen in the Moderate category with over 24% of water bodies changing to Poor or Bad status. This is particularly interesting as the baseline shows that no water bodies currently have the lowest water quality status. Table 4-5 Growth scenario WFD status of water bodies in the Anglian region and percentage change relative to the baseline (expressed as number of water bodies and percentage of the total number of water bodies) WFD Status Current EQS Change Future EQS Change Anglian region High 54 (7%) -1 (1%) 53 (7%) -2 (1%) Good 100 (14%) -33 (4%) 45 (6%) -30 (4%) Moderate 170 (23%) -72 (10) 175 (24%) -66 (9%) Poor 334 (46%) +60 (9%) 388 (53%) +54 (7%) Bad 74 (10%) +46 (6%) 71(10%) +44 (6%) Upper Bedford Ouse High 1 (1%) No change 1 (1%) No change Good 9 (10%) -1 (1%) 2 (2%) -3 (4%) Moderate 20 (22%) -12 (14%) 19 (21%) -11 (13%) Poor 50 (56%) +6 (7%) 58 (65%) +6 (7%) Bad 9 (10%) +7 (8%) 9 (10%) +8 (9%) Cam and Ely Ouse High 7 (8%) No change 7 (8%) No change Good 6 (7%) -11 (13%) 2 (2%) -8 (10%) Moderate 20 (23%) -20 (24%) 17 (20%) -23 (27%) Poor 49 (57%) +27 (31%) 57 (66%) +28 (32%) Bad 4 (5%) +4 (5%) 3 (4%) +3 (4%) Atkins Version April

31 Figure 4-11 Growth modelled WFD status against current and proposed EQS Atkins Version April

32 Summary of impact of population growth on the Anglian region Results show that the greatest impact of population growth could be an overall increase in poor status waterbodies whilst waterbodies classified as high, good or moderate would decrease in abundance. Across the entire region, model results suggest that 5% of waterbodies classified as high or good have their status downgraded to less than good. Modelled results indicate that North West Norfolk, North Norfolk and the Broadland Rivers management catchments may be the most resilient to reduced water quality as a result of population growth. The Cam and Ely Ouse, Upper Bedford Ouse, Nene, Welland and Witham catchments appear to be less resilient. 4.2 Ecological change An analysis of the impact of changes in phosphorus concentrations on overall ecological status was presented in the previous report (Atkins, 2013d) that formed part of the SAGIS investigations on the Anglian Region. This indicated that for many rivers the biological status is determined by other factors such as hydromorphology and flow and in many cases biological status is either worse or better than the phosphorus status. There is high degree of uncertainty in the relationship between phosphate concentrations and the plant community and the phosphate standards are based on the 50 percentile point in this relationship. The deterioration in phosphate concentrations indicated by the analysis of climate change and population growth suggests that the ecological status would deteriorate but this is constrained by other influences on the plant community. Climate change will affect the other influences on the biological community including water temperature and flow velocity and for many rivers this is likely to be as important as changes in phosphorus concentrations (Whitehead et al., 2009). Reduced river flows in particular are likely to have a harmful impact on the biology and this may well be more important than changes in phosphorus concentrations. Atkins Version April

33 5. Conclusions Overall, model results from this investigation indicate that phosphate concentrations could deteriorate in the future as a result of climate change and population growth. In order to maintain water quality at its current condition, measures are necessary in order to ameliorate the effects of climate change and growth. 5.1 Climate change This report has focused upon the two largest rivers that are covered by future flow datasets; the Great River Ouse and the Wensum. SAGIS modelling predicts that the Qmean and Q95 of these rivers may decrease from the present day baseline in response to future climate change. Furthermore, model results suggest that both rivers could have higher predicted phosphate concentrations in comparison to the baseline, except the Wensum in which only one of the eleven ensembles predicted higher concentrations at the downstream limit (41 Km downstream from the source). The entire investigated region is summarised as follows: Overall, Qmean and Q95 of the reaches investigated here are predicted to decrease below their baseline values in response to climate change and population growth. However, the predictions for Qmean for the Little Ouse and Q95 for the Brett are both uncertain as Qmean and Q95 could increase or decrease. The predicted reduction in Qmean and Q95 from the baseline does not necessarily equate to higher phosphate concentrations. For the majority of rivers, an increase in phosphate concentration is predicted. Lower concentrations are predicted for the Brett, Waveney and Tas. The reason for this is likely to be the loss of velocity in these rivers resulting in increased sedimentation and resultant loss of phosphate. However, although phosphate concentrations may be lower in the future, lower flows could result in depressed ecological status due to deposition of sediment. 5.2 Growth Across the entire region, 5% of waterbodies classified as high or good have their status downgraded to less than good. Across the region the modelled results imply that there would be an overall increase in poor status waterbodies. Across the region the modelled results imply that waterbodies classified as high, good or moderate would decrease in abundance. North West Norfolk, North Norfolk and the Broadland Rivers management catchments are likely to be the most resilient to population growth. The Cam and Ely Ouse, Upper Bedford Ouse, Nene, Welland and Witham catchments are likely to be the least resilient to population growth. 5.3 Ecological Change The deterioration in phosphate concentrations indicated by the analysis of climate change and population growth suggests that the ecological status would deteriorate but this is constrained by other influences on the plant community. Climate change will affect the other influences on the biological community including water temperature and flow velocity and for many rivers this is likely to be as important as changes in phosphorus concentrations. Reduced river flows in particular are likely to have a harmful impact on the biology and this may well be more important than changes in phosphorus concentrations. Atkins Version April

34 6. Recommendations for further work Both climate change and growth have been identified separately as having potentially detrimental effects on water quality. However, the combined implications are still unknown. It is recommended that an investigation be undertaken to explore future water quality which combines both the implications of climate change and growth together. It is recommended that this be done for the Upper Bedford Ouse, which is well represented by future flows data and is in an area of predicted population growth. Effective planning of water quality improvements need to be designed to be able to deal with future challenges as well as those apparent now. The success of water quality improvement measures will depend not only on their effectiveness but their longevity in addressing water quality. Following the findings of this report, it is recommended that further work be undertaken to identify measures that would improve water quality and maintain to do so into a future of uncertain climate and potential population growth. Atkins Version April

35 7. References Atkins, 2013a. Phosphorus source apportionment modelling: Model comparison. Final report for the Environment Agency, July Atkins, 2013b. River catchment selection and preparation for identifying packages of potential options for reducing phosphorus at a river catchment level. Final report for the Environment Agency, December Atkins, 2013c. Packages of potential options for reducing phosphorous at a river catchment level: Anglian region. Final report for the Environment Agency, January Atkins, 2013d. Anglian P Strategy - Modelling Support. Final report for the Environment Agency, October Environment Agency, Review of best practice in treatment and reuse/recycling of phosphorus at wastewater treatment works. Environment Agency (UK).Environment Agency (2013) Anglian priority places. Internal report Entec, Impacts of Growth on Water Quality in the East Anglian: Assessment to Support the RSS Review. Entec UK Limited Environment Agency, Anglian priority places. Internal report. Haxton T., Crooks S., Jackson C.R., Barkwith A.K.A.P., Kelvin J., Williamson J., Mackay J.D., Wang L., Davies H., Young A., Prudhomme C Future Flows Hydrology, Nakićenović, N. & Swart, R. (eds) Special Report on Emissions Scenarios. A special report of the Intergovernmental Panel on Climate Change. IPCC, Cambridge University Press, Cambridge, UK. Prudhomme, C., Crooks, S., Jackson, C., Kelvin, J. and Young, A. 2012a. Future Flows and Groundwater Levels Final Technical Report (SC090016/PN9), Centre for Ecology and Hydrology, Wallingford, 106pp. Prudhomme C., Dadson S., Morris D., Williamson J., Goodsell G., Crooks, S., Boelee L., Davies H., Buys G., Lafon T Future Flows Climate, Whitehead. P. G., Wilby, R. L., Battarbee, R. W., Kernan, M., Wade, A.J A review of the potential impacts of climate change on surface water quality. Hydrological Sciences. 54, 1, UKCP [online] UKCP09 Index: Perturbed Physics Ensemble, Available at [Accessed 21/02/14]. Atkins Version April

36 Appendices

37 Appendix A. Growth projections for the Anglian region and the implication for increased sewage treatment works flow The growth projections for the Anglian region are listed in Table A-1. This consisted of growth projection for local district area provided by the Anglian regional Environment Agency (Priority places data, internal report). Additionally, the STWs listed in Table A-1, have been identify as those likely to have increased flow due to population growth (Entec, 2010). The implication for increased sewage effluent flow was determined as follows: 1. The population increase between 2011 and 2041 was calculated for each of the local districts 2. This population increase was converted to flow (Q MD/d) using the equation below 3. The increased flow was divided equally to the STWs present in each of the local districts 4. The STWs listed in Table A-1 had their flows increases as per the dry weather flow increase mentioned in the Entec report Table A-1 Dry Weather flow increase of STWs indentify the Entec report STW Dry Weather flow increase Hitchin 36 Marston Moretaine 10 Uttons Drove 75 Dunstable 19 Leigton Linslade 14 Chalton 10 Cotton Valley 17 Tuddenham 85 Attleborough 45 Haverhill 23 A.1. References Entec (2010). Impacts of Growth on Water Quality in the East Anglian: Assessment to Support the RSS Review. Entec UK Limited Atkins Version April

38 Table A-2 Growth projections and population increase from 2011 to 2031 and the implications for increased sewage effluent flow County Area_Name 2011 Population 2041 Population Population increase Q increase (ML/d) Number of STWs Q increase per STW (ML/d) BUCKINGHAMSHIRE_COUNTY AylesburyVale CAMBRIDGESHIRE_COUNTY Fenland CAMBRIDGESHIRE_COUNTY SouthCambridgeshire CAMBRIDGESHIRE_COUNTY EastCambridgeshire CAMBRIDGESHIRE_COUNTY Huntingdonshire CAMBRIDGESHIRE_COUNTY Cambridge ESSEX_COUNTY Brentwood ESSEX_COUNTY Rochford ESSEX_COUNTY Tendring ESSEX_COUNTY Uttlesford ESSEX_COUNTY Chelmsford ESSEX_COUNTY Colchester ESSEX_COUNTY Maldon ESSEX_COUNTY Braintree ESSEX_COUNTY Basildon ESSEX_COUNTY CastlePoint LEICESTERSHIRE_COUNTY Harborough LINCOLNSHIRE_COUNTY WestLindsey LINCOLNSHIRE_COUNTY SouthKesteven LINCOLNSHIRE_COUNTY SouthHolland LINCOLNSHIRE_COUNTY Boston LINCOLNSHIRE_COUNTY NorthKesteven LINCOLNSHIRE_COUNTY EastLindsey LINCOLNSHIRE_COUNTY Lincoln Atkins Version April

39 County Area_Name 2011 Population 2041 Population Population increase Q increase (ML/d) Number of STWs Q increase per STW (ML/d) NORFOLK_COUNTY NorthNorfolk NORFOLK_COUNTY GreatYarmouth NORFOLK_COUNTY SouthNorfolk NORFOLK_COUNTY King slynn&westnorfolk NORFOLK_COUNTY Breckland NORFOLK_COUNTY Norwich NORTHAMPTONSHIRE_COUNTY SouthNorthamptonshire NORTHAMPTONSHIRE_COUNTY EastNorthamptonshire NORTHAMPTONSHIRE_COUNTY Daventry NORTHAMPTONSHIRE_COUNTY Wellingborough NORTHAMPTONSHIRE_COUNTY Kettering NORTHAMPTONSHIRE_COUNTY Northampton NORTHAMPTONSHIRE_COUNTY Corby NOTTINGHAMSHIRE_COUNTY Bassetlaw SUFFOLK_COUNTY Waveney SUFFOLK_COUNTY Babergh SUFFOLK_COUNTY SuffolkCoastal SUFFOLK_COUNTY StEdmundsbury SUFFOLK_COUNTY ForestHeath SUFFOLK_COUNTY MidSuffolk SUFFOLK_COUNTY Ipswich BEDFORD_(B) Bedford CENTRAL_BEDFORDSHIRE CentralBedfordshire CITY_OF_PETERBOROUGH_(B) Peterborough LUTON_(B) NorthHertfordshire MILTON_KEYNES_(B) Milton Keynes Atkins Version April

40 County Area_Name 2011 Population 2041 Population Population increase Q increase (ML/d) Number of STWs NORTH_EAST_LINCOLNSHIRE_(B) NorthEastLincolnshire NORTH_LINCOLNSHIRE_(B) NorthLincolnshire Q increase per STW (ML/d) RUTLAND Rutland SOUTHEND-ON-SEA_(B) Southend-on-Sea THURROCK_(B) Thurrock NORFOLK_COUNTY Broadland Atkins Version April

41 Monthly percentage change from baseline Monthly percentage change from baseline Appendix B. Future Flow Data B.1. Chater at Foster Bridge Monthly Change Factors: 2050s ( ) 60.0% 40.0% 20.0% 0.0% -20.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -80.0% Month Figure B-1 Chater Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-2 Chater Q95 change factors (as percent deviation from the baseline) Atkins Version April

42 Monthly percentage change from baseline Monthly percentage change from baseline B.2. Kym at Meagre Farm Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% -40.0% -60.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % % Month Figure B-3 Kym Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 60.0% 40.0% 20.0% 0.0% -20.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -80.0% Month Figure B-4 Kym Q95 change factors (as percent deviation from the baseline) Atkins Version April

43 Monthly percentage change from baseline Monthly percentage change from baseline B.3. Lark at Temple Monthly Change Factors: 2050s ( ) 50.0% 40.0% 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -50.0% Month Figure B-5 Lark Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 120.0% 100.0% 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-6 Lark Q95 change factors (as percent deviation from the baseline) Atkins Version April

44 Monthly percentage change from baseline Monthly percentage change from baseline B.4. Tove at Cappenham Bridge Monthly Change Factors: 2050s ( ) 60.0% 40.0% 20.0% 0.0% -20.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -80.0% Month Figure B-7 Tove Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-8 Tove Q95 change factors (as percent deviation from the baseline) Atkins Version April

45 Monthly percentage change from baseline Monthly percentage change from baseline B.5. Thet at Melford Bridge Monthly Change Factors: 2050s ( ) 40.0% 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-9 Thet Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-10 Thet Q95 change factors (as percent deviation from the baseline) Atkins Version April

46 Monthly percentage change from baseline Monthly percentage change from baseline B.6. Bedford Ouse at Offord Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-11 Bedford Ouse Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -40.0% Month Figure B-12 Bedford Ouse Q95 change factors (as percent deviation from the baseline) Atkins Version April

47 Monthly percentage change from baseline Monthly percentage change from baseline B.7. Rhee at Wimpole Monthly Change Factors: 2050s ( ) 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-13 Rhee Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-14 Rhee Q95 change factors (as percent deviation from the baseline) Atkins Version April

48 Monthly percentage change from baseline Monthly percentage change from baseline B.8. Springside at Whitebridge Monthly Change Factors: 2050s ( ) 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-15 Springside Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-16 Springside Q95 change factors (as percent deviation from the baseline) Atkins Version April

49 Monthly percentage change from baseline Monthly percentage change from baseline B.9. Thet at Bridgham Monthly Change Factors: 2050s ( ) 40.0% 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-17 Thet Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 200.0% 150.0% 100.0% 50.0% 0.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % % Month Figure B-18 Thet Q95 change factors (as percent deviation from the baseline) Atkins Version April

50 Monthly percentage change from baseline Monthly percentage change from baseline B.10. Stanford Water at Buckenham Tofts 30.0% Monthly Change Factors: 2050s ( ) 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-19 Stanford Water Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 200.0% 150.0% 100.0% 50.0% 0.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % % Month Figure B-20 Stanford Water Q95 change factors (as percent deviation from the baseline) Atkins Version April

51 Monthly percentage change from baseline Monthly percentage change from baseline B.11. Little Ouse at Knettishall 40.0% Monthly Change Factors: 2050s ( ) 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-21 Little Ouse Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 200.0% 150.0% 100.0% 50.0% 0.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % % Month Figure B-22 Little Ouse Q95 change factors (as percent deviation from the baseline) Atkins Version April

52 Monthly percentage change from baseline Monthly percentage change from baseline B.12. Tas at Shotesham 60.0% Monthly Change Factors: 2050s ( ) 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-23 Little Ouse Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 300.0% 250.0% 200.0% 150.0% 100.0% 50.0% 0.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % % Month Figure B-24 Little Ouse Q95 change factors (as percent deviation from the baseline) Atkins Version April

53 Monthly percentage change from baseline Monthly percentage change from baseline B.13. Waveney at Needham Mill 40.0% Monthly Change Factors: 2050s ( ) 20.0% 0.0% -20.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -80.0% Month Figure B-25 Waveney Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-26 Waveney Q95 change factors (as percent deviation from the baseline) Atkins Version April

54 Monthly percentage change from baseline Monthly percentage change from baseline B.14. Wensum at Fakenham 40.0% Monthly Change Factors: 2050s ( ) 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-27 Wensum Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 140.0% 120.0% 100.0% 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-28 Wensum Q95 change factors (as percent deviation from the baseline) Atkins Version April

55 Monthly percentage change from baseline Monthly percentage change from baseline B.15. Wensum at Swanton Morley 40.0% Monthly Change Factors: 2050s ( ) 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% -50.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -70.0% Month Figure B-29 Wensum Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 250.0% 200.0% 150.0% 100.0% 50.0% 0.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % % Month Figure B-30 Wensum Q95 change factors (as percent deviation from the baseline) Atkins Version April

56 Monthly percentage change from baseline Monthly percentage change from baseline B.16. Stiffkey at Warham 40.0% Monthly Change Factors: 2050s ( ) 30.0% 20.0% 10.0% 0.0% -10.0% -20.0% -30.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-31 Stiffkey Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 160.0% 140.0% 120.0% 100.0% 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-32 Stiffkey Q95 change factors (as percent deviation from the baseline) Atkins Version April

57 Monthly percentage change from baseline Monthly percentage change from baseline B.17. Gipping at Stowmarket 80.0% Monthly Change Factors: 2050s ( ) 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-33 Gipping Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 200.0% 150.0% 100.0% 50.0% 0.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % % Month Figure B-34 Gipping Q95 change factors (as percent deviation from the baseline) Atkins Version April

58 Monthly percentage change from baseline Monthly percentage change from baseline B.18. Brett at Hadleigh 60.0% Monthly Change Factors: 2050s ( ) 40.0% 20.0% 0.0% -20.0% -40.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -80.0% Month Figure B-35 Brett Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-36 Brett Q95 change factors (as percent deviation from the baseline) Atkins Version April

59 Monthly percentage change from baseline Monthly percentage change from baseline B.19. Belchamp Brook at Bardfield Bridge 80.0% Monthly Change Factors: 2050s ( ) 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-37 Belchamp Brook Q change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 140.0% 120.0% 100.0% 80.0% 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-38 Belchamp Brook Q95 change factors (as percent deviation from the baseline) Atkins Version April

60 Monthly percentage change from baseline Monthly percentage change from baseline B.20. Chelmer at Churchend 80.0% Monthly Change Factors: 2050s ( ) 60.0% 40.0% 20.0% 0.0% -20.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % -60.0% Month Figure B-39 Belchamp Brook Q95 change factors (as percent deviation from the baseline) Monthly Change Factors: 2050s ( ) 350.0% 300.0% 250.0% 200.0% 150.0% 100.0% 50.0% 0.0% Q0 Q3 Q4 Q6 Q9 Q8 Q10 Q14 Q11 Q13 Q % % Month Figure B-40 Belchamp Brook Q95 change factors (as percent deviation from the baseline) Atkins Version April

61 Q (Ml/d) Appendix C. Climate Change River Reports C.1. The River Brett The implications of Qmean and Q95 upon the River Brett based upon the climate projections of the eleven future flow ensembles are shown in Figure C-1 and Figure C-2. The future flow projections indicate the uncertainty of climate prediction due to the range of Qmean and Q95 values either side of the baseline. C.1.1. Qmean It is observed that the majority of the future flow ensembles produce lower annual flow in comparison to the baseline. At the head of the river the baseline Qmean is 45 ML/d, whereas the projected range from the future flow ensembles is 11 to 48 ML/d (Figure C-1). However, at the head, eight of the eleven ensembles predict lower mean flow. At the river midpoint (11 KM from source) the baseline Qmean is 71 ML/d, whereas the projected range of the future flow ensembles is 35 to 76 ML/d (Figure C-1). However, at this midpoint, ten of the eleven ensembles predict lower mean flow. At the downstream limit (23 KM from the source) the baseline Qmean is 87 ML/d, whereas the projected range of the future flow ensembles is 54 to 92 ML/d (Figure C-1). However, at the head, nine of the eleven ensembles predict lower mean flow Baseline flow Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q9 0 Figure C Distance (KM) Brett Q C.1.2. Q95 In contrast to the modelled results for Qmean, results suggest no overall predicted reduction or increase in annual Q95 in comparison to the baseline.. Atkins Version April

62 Q (Ml/d) At the head of the river the baseline Q95 is 2 ML/d, whereas the projected range from the future flow ensembles is 1 to 6 ML/d (Figure C-2). At the head, four of the eleven ensembles predict lower Q95. At the river midpoint (11 KM from source) the baseline Q95 is 5 ML/d, whereas the projected range of the future flow ensembles is 3 to 9 ML/d (Figure C-2). At this midpoint, five of the eleven ensembles predict lower Q95. At the downstream limit (23 KM from the source) the baseline Q is 8 ML/d, whereas the projected range of the future flow ensembles is 6 to 12 ML/d (Figure C-2). At this downstream limit, five of the eleven ensembles predict lower Q Baseline Q95 Ensemble Q0 Ensemble Q10 40 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 35 Ensemble Q6 Ensemble Q8 Ensemble Q Figure C Distance (KM) Brett Q95 C.1.3. Phosphate concentration An overall reduction in annual average phosphate concentration in comparison to the baseline is modelled (Figure C-3). The majority of the future flow ensembles predict lower concentrations in comparison to the baseline. This may be due to the lower velocities that could result from a reduced Qmean. Within SIMCAT velocity has a direct relationship with settling rate. Thus in the case of the River Brett, lower velocities could result in greater settlement of phosphate and removal from the water column. At the river midpoint (11 KM from source) the baseline concentration is 0.34 mg/l, whereas the projected range from the future flow ensembles is 0.20 to 0.41 mg/l (Figure C-3). At this midpoint, four of the eleven ensembles have higher concentrations. At the downstream limit (23 KM from the source) the baseline concentration is 0.27 mg/l, whereas the projected range from the future flow ensembles is 0.16 to 0.28 mg/l (Figure C-3). At this downstream limit, three of the eleven ensembles have higher predicted concentration. Atkins Version April

63 PO4 Concentration (mg/l) Baseline annual mean Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Figure C Distance (KM) Brett phosphate concentration C.2. The River Waveney Modelled results for Qmean and Q95 in the Waveney related to the climate projections of the eleven future flow ensembles are shown in Figure C-4 and Figure C-5. The future flow projections indicate a uncertainty impact of the climate prediction due to the range of Q and Q95 values being either side of the baseline. C.2.1. Qmean It is observed that the majority of the future flow ensembles predicted lower annual flow in comparison to the baseline. At the river midpoint (10 KM downstream of the source) the baseline Q is 25 ML/d, whereas the projected range from the future flow ensembles is 8 to 57 ML/d (Figure C-4). However, at this midpoint, seven of the eleven ensembles predict lower mean flow. At the downstream limit (18 KM downstream of the source) the baseline Q is 218 ML/d, whereas the projected range from the future flow ensembles is 131 to 255 ML/d (Figure C-4). However, at the downstream limit, nine of the eleven ensembles predict lower mean flow. Atkins Version April

64 Q (Ml/d) Baseline flow Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Figure C Distance (KM) Waveney Qmean C.2.2. Q95 It is modelled that the majority of the future flow ensembles produce lower Q95 in comparison to the baseline. At the river midpoint (10 KM downstream of the source) the baseline Q95 is 25 ML/d, whereas the projected range from the future flow ensembles is 8 to 57 ML/d (Figure C-5). At this midpoint, eight of the eleven ensembles predict lower Q95. At the downstream limit (18 KM downstream of the source) the baseline Q is 8 ML/d, whereas the projected range from the future flow ensembles is 6 to 12 ML/d (Figure C-5). At this downstream limit, five of the eleven ensembles predict lower Q95. Atkins Version April

65 Q (Ml/d) Baseline Q95 Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q9 5 0 Figure C Distance (KM) Waveney Q95 C.2.3. Phosphate concentration From 11 KM from the source, results suggest a reduction in annual average phosphate concentration in comparison to the baseline (Figure C-6). From this point all future flow ensembles predict lower concentrations in comparison to the baseline. This may be driven by lower velocities that result from a reduced Qmean. Within SIMCAT velocity has a direct relationship with settling rate. Thus in the case of the River Waveney, lower velocities could result in greater settlement of phosphate and removal from the water column. At the river midpoint (10 KM downstream of the source) the baseline concentration is 0.32 mg/l, whereas the projected range from the future flow ensembles is 0.13 to 0.76 mg/l (Figure C-6). At this midpoint, seven of the eleven ensembles predict higher concentrations. At the downstream limit (18 KM downstream of the source) the baseline concentration is 0.61 mg/l, whereas the projected range from the future flow ensembles is 0.19 to 0.38 mg/l (Figure C-6). At this downstream limit, all of the eleven ensembles predict lower concentrations. Atkins Version April

66 PO4 Concentration (mg/l) Baseline annual mean Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Figure C Distance (KM) Waveney phosphate concentration C.3. Tas The implications for Qmean and Q95 in the Tas of the eleven future flow ensembles are shown in Figure C-7 and Figure C-8. The future flow projections indicate a range of potential climate prediction as evidenced by the range of Q and Q95 values being either side of the baseline. C.3.1. Qmean It is modelled that the majority of the future flow ensembles produce lower annual flow in comparison to the baseline. At the river midpoint (15 KM downstream of source) the baseline Q is 37 ML/d, whereas the projected range from the future flow ensembles is 12 to 46 ML/d (Figure C-7). However, at this midpoint, nine of the eleven ensembles predict lower mean flow. At the downstream limit (30 KM downstream of the source) the baseline Q is 103 ML/d, whereas the projected range from the future flow ensembles is 42 to 114 ML/d (Figure C-7). However, at the downstream limit, nine of the eleven ensembles predict lower mean flow. Atkins Version April

67 Q (Ml/d) Baseline flow Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Figure C Distance (KM) Tas Qmean C.3.2. Q95 It is modelled that the majority of the future flow ensembles produce lower Q95 in comparison to the baseline. At the river midpoint (15 KM downstream of the source) the baseline Q95 is 5 ML/d, whereas the projected range the future flow ensembles is 2 to 6 ML/d (Figure C-8). At this midpoint, nine of the eleven ensembles predict lower Q95. At the downstream limit (30 KM downstream of the source) the baseline Q95 is 13 ML/d, whereas the projected range from the future flow ensembles is 8 to 14 ML/d (Figure C-8). At this midpoint, nine of the eleven ensembles predicted lower Q95. Atkins Version April

68 Q (Ml/d) Baseline Q95 Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Figure C Distance (KM) Tas Q95 C.3.3. Phosphate concentration At 13 KM from the source, modelled results suggest a reduction in annual average PO4 concentration in comparison to the baseline (Figure C-9). From this point the majority of future flow ensembles predict lower concentrations in comparison to the baseline. This could maybe due to the lower velocities that would result from a reduced Qmean. Within SIMCAT, velocity has a direct relationship with settling rate. Thus in the case of the Tas, lower velocities could result in greater settlement of PO4 and removal from the water column in the lower reaches. At the river midpoint (15 KM downstream of the source) the baseline concentration is 0.37 mg/l, whereas the projected range from the future flow ensembles is 0.23 to 0.83 mg/l (Figure C-9). At this midpoint, two of the eleven ensembles predicted higher concentrations. At the downstream limit (30 KM downstream of the source) the baseline concentration is 0.50 mg/l, whereas the projected range from the future flow ensembles is 0.29 to 0.62 mg/l (Figure C-9). At this downstream limit, one of the eleven ensembles predicted higher concentrations. Atkins Version April

69 PO4 Concentration (mg/l) Baseline annual mean Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Figure C Distance (KM) Tas Phosphate concentration C.4. Wensum Thes impact of the eleven future flow ensembles on Qmean and Q95 in the Wensum are shown in Figure C- 10 and Figure C-11. The future flow projections indicate a range of Q and Q95 values either side of the baseline. C.4.1. Q It is modelled that the majority of the future flow ensembles produce lower annual flow in comparison to the baseline. At the river midpoint (21 KM from source) the baseline Q is 128 ML/d, whereas the projected range from the future flow ensembles is 63 to 106 ML/d (Figure C-10). At this midpoint, all eleven ensembles predict lower mean flow. At the downstream limit (41 KM from the source) the baseline Q is 252 ML/d, whereas the projected range from the future flow ensembles is 153 to 261 ML/d (Figure C-10). At the downstream limit, nine of the eleven ensembles predict lower mean flow. Atkins Version April

70 Q (Ml/d) Baseline flow Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q Distance (KM) Figure C-10 Wensum Qmean C.4.2. Q95 It is modelled that the majority of the future flow ensembles produce lower Q95 in comparison to the baseline. At the river midpoint (21 KM downstream of the source) the baseline Q95 is 23 ML/d, whereas the projected range from the future flow ensembles is 9 to 18 ML/d (Figure C-11). At this midpoint, all eleven of the ensembles predict lower mean flow. At the downstream limit (41 KM downstream of the source) the baseline Q is 252 ML/d, whereas the projected range from the future flow ensembles is 42 to 25 ML/d (Figure C-11). At the downstream limit, eight of the eleven ensembles predict lower mean flow. Atkins Version April

71 Q (Ml/d) Baseline Q95 Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q Distance (KM) Figure C-11 Wensum Q95 C.4.3. Phosphate concentration Modelled results indicate that up to 25 KM from the source, an increase in annual average phosphate concentration compared to the baseline for every ensemble tested (Figure C-12). From this point up to 32 KM from the source the majority of future flow ensembles predict higher concentrations in comparison to the baseline. From this point on, the majority of the flow ensembles predict lower concentrations. This may be due to the lower velocities that could result from a reduced Qmean predicted by the Future Flows ensembles. Within SIMCAT velocity has a direct relationship with settling rate. Thus in the case of the Wensum, lower velocities could result in greater settlement of phosphate and removal from the water column at the lower reaches. At the river midpoint (21 KM downstream of the source) the baseline concentration is 0.09 mg/l, whereas the projected range from the future flow ensembles is 0.10 to 0.17 mg/l (Figure C-12). At this midpoint, all of the eleven ensembles predicted higher concentrations. At the downstream limit (41 KM downstream of the source) the baseline concentration is 0.16 mg/l, whereas the projected range from the future flow ensembles is 0.10 to 0.18 mg/l (Figure C-12). At this downstream limit, one of the eleven ensembles predicted higher concentrations. Atkins Version April

72 PO4 Concentration (mg/l) Baseline annual mean Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q Distance (KM) Figure C-12 Wensum phosphate concentration C.5. Wissey The impact of the eleven future flow ensembles on the Qmean and Q95 in the Wissey b are shown in Figure C-13 and Figure C-14. The future flow projections indicate uncertainty in the climate change prediction due to the range of Q and Q95 values being either side of the baseline. C.5.1. Qmean It is modelled that the majority of the future flow ensembles produce lower annual flow in comparison to the baseline. At the river midpoint (17 KM from source) the baseline Q is 54 ML/d, whereas the projected range from the future flow ensembles is 8 to 136 ML/d (Figure C-13). At this midpoint, ten of the eleven ensembles predict lower mean flow. At the downstream limit (31 KM from the source) the baseline Q is 182 ML/d, whereas the projected range from the future flow ensembles is 59 to 305 ML/d (Figure C-13). At the downstream limit, ten of the eleven ensembles predict lower mean flow. Atkins Version April

73 Q (Ml/d) Baseline flow Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q Distance (KM) Figure C-13 Wissey Qmean C.5.2. Q95 It is modelled that the majority of the future flow ensembles produce lower Q95 in comparison to the baseline. At the river midpoint (17 KM from source) the baseline Q95is 13 ML/d, whereas the projected range from the future flow ensembles is 1 to 15 ML/d (Figure C-14). At this midpoint, ten of the eleven ensembles predict lower Q95. At the downstream limit (31 KM from the source) the baseline Q95 is 46 ML/d, whereas the projected range from the future flow ensembles is 6 to 34 ML/d (Figure C-14). At the downstream limit, all eleven ensembles predict lower Q95. Atkins Version April

74 Q95 (Ml/d) Baseline Q95 Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Distance (KM) Figure C-14 Wissey Q95 C.5.3. Phosphate concentration Over the entire 31 KM length investigated, a predicted increase in annual average phosphate concentration compared to the baseline can be observed for all except one ensemble (Figure C-15). At the river midpoint (17 KM downstream of the from source) the baseline concentration is 0.17 mg/l, whereas the projected range from the future flow ensembles is 0.12 to 1.56 mg/l (Figure C- 15). At this midpoint, ten of the eleven ensembles predict higher concentrations. At the downstream limit (31 KM downstream of the source) the baseline concentration is 0.11 mg/l, whereas the projected range from the future flow ensembles is 0.10 to 0.51 mg/l (Figure C-15). At this downstream limit, ten of the eleven ensembles predicted higher concentrations. Atkins Version April

75 PO4 Concentration (mg/l) Baseline annual mean Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Distance (KM) Figure C-15 Wissey phosphate concentration C.6. Thet The impact of the eleven future flow ensembles on the Qmean and Q95 in the Thet are shown in Figure C- 16 and Figure C-17. C.6.1. Qmean It is modelled that the majority of the future flow ensembles produce lower annual flow in comparison to the baseline. At the river midpoint (16 KM from source) the baseline Q is 160 ML/d, whereas the projected range from the future flow ensembles is 45 to 136 ML/d (Figure C-16). At this midpoint, all eleven ensembles predicted lower mean flow. At the downstream limit (35 KM from the source) the baseline Q is 229 ML/d, whereas the projected range from the future flow ensembles is 85 to 245 ML/d (Figure C-16). At the downstream limit, nine of the eleven ensembles predicted lower mean flow. Atkins Version April

76 Q (Ml/d) Baseline flow Ensemble Q10 Ensemble Q13 Ensemble Q16 Ensemble Q4 Ensemble Q8 Ensemble Q0 Ensemble Q11 Ensemble Q14 Ensemble Q3 Ensemble Q6 Ensemble Q Distance (KM) Figure C-16 Thet Qmean C.6.2. Q95 It is modelled that the majority of the future flow ensembles produce lower annual flow in comparison to the baseline. At the river midpoint (16 KM from source) the baseline Q95 is 34 ML/d, whereas the projected range from the future flow ensembles is 8 to 23 ML/d (Figure C-17). At this midpoint, all eleven ensembles predict lower mean flow. At the downstream limit (35 KM from the source) the baseline Q95 is 229 ML/d, whereas the projected range from the future flow ensembles is 8 to 23 ML/d (Figure C-17). At the downstream limit, ten of the eleven ensembles predict lower mean flow. Atkins Version April

77 Q (Ml/d) Baseline Q95 Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Distance (KM) Figure C-17 Thet Q95 C.6.3. Phosphate concentration Over the 35 KM length investigated, an increase in annual average phosphate concentration compared to the baseline can be observed for all except one ensemble Figure C-18. At the river midpoint (16 KM from source) the baseline concentration is 0.09 mg/l, whereas the projected range from the future flow ensembles is 0.13 to 0.43 mg/l (Figure C-18). At this midpoint, all eleven ensembles predict higher concentrations. At the downstream limit (35 KM from the source) the baseline concentration is 0.07 mg/l, whereas the projected range from the future flow ensembles is 0.07 to 0.23 mg/l (Figure C-18). At this downstream limit, ten of the eleven ensembles predict higher concentrations. Atkins Version April

78 PO4 Concentration (mg/l) Baseline annual mean Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Distance (KM) Figure C-18 Thet phosphate concentration C.7. Little Ouse The impact of the eleven future flow ensembles on the Qmean and Q95 in the Little Ouse are shown in Figure C-19 and Figure C-20. The future flow projections indicate a range of Q and Q95 values being either side of the baseline. C.7.1. Qmean The future flow ensembles produce a range of flows that span either side of the baseline demonstrating a range of uncertainty in the implications of climate change upon this river. At the river midpoint (13 KM from source) the baseline Q is 71 ML/d, whereas the projected range from the future flow ensembles is 40 to 113 ML/d (Figure C-19). At this midpoint, six of the eleven ensembles predict lower mean flow. At the downstream limit (31 KM from the source) the baseline Q is 224 ML/d, whereas the projected range from the future flow ensembles is 156 to 270 ML/d (Figure C-19). At the downstream limit, four of the eleven ensembles predict lower mean flow. Atkins Version April

79 Q (Ml/d) Baseline flow Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Distance (KM) Figure C-19 Little Ouse Qmean C.7.2. Q95 Although the future flow ensembles produce a range of flows that span either side of the baseline, it is results indicate that the majority of the future flow ensembles predict lower Q95. At the river midpoint (13 KM from source) the baseline Q95 is 12 ML/d, whereas the projected range from the future flow ensembles is 4 to 16 ML/d (Figure C-20). At this midpoint, eight of the eleven ensembles predict lower mean flow. At the downstream limit (31 KM from the source) the baseline Q is 43 ML/d, whereas the projected range from the future flow ensembles is 18 to 37 ML/d (Figure C-20). At the downstream limit, all eleven ensembles predict lower mean flow. Atkins Version April

80 Q (Ml/d) Baseline Q95 Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Distance (KM) Figure C-20 Little Ouse Q95 C.7.3. Phosphate concentration Over the 23 KM length investigated, the majority of the ensembles predict higher concentrations (Figure C- 21). At the river midpoint (13 KM from source) the baseline concentration is 0.18 mg/l, whereas the projected range from the future flow ensembles is 0.13 to 0.45 mg/l ((Figure C-21). At this midpoint, nine of the eleven ensembles predict higher concentrations. At the downstream limit (23 KM from the source) the baseline concentration is 0.22 mg/l, whereas the projected range from the future flow ensembles is 0.23 to 0.43 mg/l ((Figure C-21). At this downstream limit, all eleven ensembles predict higher concentrations. Atkins Version April

81 PO4 Concentration (mg/l) Baseline annual mean Ensemble Q0 Ensemble Q10 Ensemble Q11 Ensemble Q13 Ensemble Q14 Ensemble Q16 Ensemble Q3 Ensemble Q4 Ensemble Q6 Ensemble Q8 Ensemble Q Distance (KM) Figure C-21 Little Ouse phosphate concentration Atkins Version April

82 Appendix D. UKCP09 Comparison As identified in Section 3.7, one of the limitations of the Future Flows Hydrology dataset is that it is only based on an 11-member ensemble and so does not explore the full range of model uncertainty captured by the UKCP09 probabilistic climate projections. Additionally, the dataset was only produced for the Medium emissions scenario. For selected catchments monthly percentage change factors for flow are available for the full 10,000 samples of UKCP09 (for Medium emissions/2050s, Medium emissions/2080s and High emissions/2050s). For these catchments it is therefore possible to compare the full range of samples from UKCP09 with the 11 change factors for Future Flows. The comparison has therefore been carried out for the following catchments for which UKCP09 data are available: Kym at Meagre Farm Stringside at Whitebridge Waveney at Needham Mill Cumulative distribution functions (CDFs) were plotted for the 10,000 UKCP09 change factors for each catchment. The 11 Q Mean change factors calculated from Future Flows Hydrology for this study were then plotted on the same graph to allow direct comparison. Comparisons were made with the UKCP09 change factors for the Medium and High emissions for the 2050s. Figure D-3 to Figure D-3 show the resulting graphs for annual factors under Medium emissions for the three catchments. It can be seen that the Future Flows change factors encompass much of the range in UKCP09 typically at least from the 10 th to the 90 th percentile. For change factors for individual months, a similar pattern is seen, though there are some instances where the Future Flows change factors are narrower; for example, for Waveney at Needham Hill, January change factors cover the range from the 40 th to the 90 th percentile of UKCP09 (see Figure D-4). However, predominantly the 11-member ensemble for Future Flows gives a good representation of the range in the UKCP09 projections. Figure D-1 UKCP09 and Future Flows Comparison of Annual Change Factors for Kym at Meagre Farm (Medium emissions for the 2050s) Atkins Version April

83 Figure D-2 UKCP09 and Future Flows Comparison of Annual Change Factors for Stringside at Whitebridge (Medium emissions for the 2050s) Figure D-3 UKCP09 and Future Flows Comparison of Annual Change Factors for Waveney at Needham Mill (Medium emissions for the 2050s) Atkins Version April

84 Figure D-4 UKCP09 and Future Flows Comparison of January Change Factors for Waveney at Needham Mill (Medium emissions for the 2050s) The comparison using the High emissions UKCP09 change factors (with the Future Flows change factors under Medium emissions) do not show substantial differences. Figure D-5 and Figure D-6 show the January change factors for Kym at Meagre Farm for Medium and High emissions respectively. There is a small shift in the CDF towards higher change factors (most noticeable above the 95 th percentile), but there is no difference in the range that the Future Flows change factors cover. The equivalent graphs for June again show small differences (see Figure D-7 and Figure D-8). In this instance Future Flows covers the 10 th to 95 th percentiles of UKCP09 under Medium emissions, which shifts to 15 th to 95 th percentiles for High emissions. These results suggest that the Future Flows Hydrology provide a good representation of the range in the full 10,000 samples of UKCP09. Future Flows Q Mean change factors predominantly cover at least the 10 th to 90 th percentile range of UKCP09, though there are instances where they are narrower for some months. It should therefore be noted that Future Flows might not adequately represent some of the extremes (high and low) of the UKCP09 range, particularly as they are only available for the Medium emissions scenario. Atkins Version April

85 Figure D-5 UKCP09 and Future Flows Comparison of January Change Factors for Kym at Meagre Farm (Medium emissions for the 2050s) Figure D-6 UKCP09 and Future Flows Comparison of January Change Factors for Kym at Meagre Farm (High emissions for the 2050s) Atkins Version April

86 Figure D-7 UKCP09 and Future Flows Comparison of June Change Factors for Kym at Meagre Farm (Medium emissions for the 2050s) Figure D-8 UKCP09 and Future Flows Comparison of June Change Factors for Kym at Meagre Farm (High emissions for the 2050s) Atkins Version April

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