Poole Harbour Consent Order Technical Document

Recommendations to deliver Favourable Status across Poole Harbour Catchment

DRAFT for consultation

18 May 2018

Prepared by:

Giles Bryan: Environment Agency Alun James: Environment Agency Rosanne Broome: Environment Agency Contributions from

Karen Edwards Environment Agency Douglas Kite Natural England Andrew Nicholson: Natural England Sarah Sanders Natural England

Supporting information Richard Gooday, Paul Newell Price: ADAS Ruth Barden: Wessex Water

Contents Executive Summary ...... 7 1.0 Introduction...... 9 2.0 Background ...... 9 2.1 Conservation objectives ...... 9 2.2 Conservation Status of Poole Harbour Catchment ...... 10 2.3 Measures put under Nutrient Management Plan to achieve conservation objectives. 10 3.0 Measures put in Place Since 2013 & Review of catchment Targets for the Purpose of the Consent Order ...... 11 3.1 Conservation Objective Targets ...... 11 3.2 Measures implemented or proposed to be implemented since 2013 ...... 12 3.3 NMP reduction strategy ...... 13 4.0 Mechanisms in place to deliver catchment objectives & Effectiveness of these measures...... 13 4.1 Mechanisms and measures put in place to deliver catchment objectives ...... 13 5.0 Updated Evidence & Catchment Objectives ...... 15 5.1 Source Apportionment & Nutrient reduction from the current strategy ...... 15 6.0 Macroalgae Modelling: Current and Future Scenarios ...... 19 6.1 Macro-algae densities modelled from 2010-11, 2013-17 and NMP Scenarios...... 19 6.2: Future Water Quality Targets required to meet model macroalgae density and threshold density targets...... 22 6.3 Modelled nutrient loading required to achieve macroalgae targets...... 25 6.4 Point Source Measures to deliver macroalgae targets ...... 27 6.5: Diffuse Measures to deliver macroalgae targets ...... 28 6.5 Alternative Measures to Deliver Diffuse Pollution Reduction: Wetland Creation...... 32 6.6 Recommended in combination Measures to Deliver Water Quality Improvements .... 33 7.0 Mechanisms and timescales to Deliver Favourable Conservation Targets...... 35 7.1 Point Source Mechanisms to Implement Measures ...... 35 7.2: Mechanisms to deliver diffuse pollution reductions and measures...... 36 7.2:1 Current legal powers to prevent pollution ...... 36 7.2.2: Recommended diffuse pollution mechanism & measures ...... 36 8.0 Stakeholders & Engagement ...... 39 9.0 Cost effectiveness ...... 40 10.0 Recommendations ...... 40 Appendix 1 : Summary of Poole Harbour dynamic Combined Phytoplankton and Macroalgae (CPM) Modelling- Calibration Study. Edwards 2018 ...... 45 Appendix 2: Water Quality and Macroalgae Modelling of Poole Harbour: Estimated the required reduction in nutrient to achieve acceptable densities of Macroalgae; James, Edward & Bryan 2018...... 47

Appendix 3: Background information for understanding the catchment situation on nitrogen nutrient enrichment in the Poole Harbour Natura 2000 site: Kite & Nicholson 2018 ...... 49 Appendix 4: Phosphorus Sources Across the Poole Harbour Catchment & Apportionment; Total Inorganic Phosphorus (TP) & Orthopho-phosphorus Bryan 2018...... 51 Appendix 5; Trends in total oxidised nitrogen (TON) in surface waters in the Poole Harbour catchment, 1976 to 2016; Environment Agency Wessex Area Analysis and Reporting Team. Draft October 2016 ...... 53

Executive Summary In 2015 the World Wildlife Fund UK, the Angling Trust and Fish Legal undertook a Judicial Review (JR) against the Secretary of State for the Environment, Food and Rural Affairs and the Environment Agency (EA). It was based on the perceived non-consideration of Water Protection Zones (WPZs), to deliver measures to tackle diffuse water pollution impacting on water-dependent Natura 2000 (N2K) sites. As a result of the JR the EA, working with Natural England (NE), undertook to evaluate whether the existing measures and mechanisms to tackle pollution will lead to the improvements in water quality necessary to meet the conservation objectives for each N2K site. This document, represents this review for the Poole Harbour catchment. Since publishing the Nutrient Management Plan (NMP) “Strategy for Managing Nitrogen across the Poole Harbour Catchment to 2035” in 2013, advice on our interpretation of conservation objectives and standards used for the macroalgae abundance, have been updated. These have been based on emerging scientific evidence. The primary conclusions from this are that: - a lower average modelled biomass of

This is a reduction from the value used in the NMP to describe when partial success of the NMP will be observed (NMP Section 1.2). Macroalgae modelling now suggests that to achieve these targets, Nitrate loads need to be reduced to the target set in the NMP (c1730 tonnes/N/yr) and Orthophosphorus reduced to 20 -21.5 tonnes OP/yr from their current levels of c2300 tonnes N/yr & c51 tonnes OP/yr or 71 tonnes TP/yr. To achieve this, additional measures are needed to reduce both diffuse and point-source pollution. Based on current trends, the voluntary uptake of agricultural mitigation measures will not meet the required reduction in pollution. Since the publication of the NMP the farming community has worked hard to start to implement the findings of the NMP. However evidence now indicates that because of the scale of N & P reduction required, to increase the confidence in delivery measures fundamental to delivering diffuse pollution reduction and maximum leaching targets for nitrate and phosphorus should be given regulatory backing through a Water Protection Zone or other mechanisms. Details regarding these measures should be developed in partnership with the appropriate stakeholders and or their representatives and where appropriate, further support and incentives should be made available to assist farmers in delivering any obligations above those that might be expected in other parts of the country. Since publication the NMP, Wessex Water have also implemented measures to reduce the impact of their discharges on the water environment, including their innovative NTrade system, offsetting 40 tonnes N/yr to mitigate for projected growth. Modelling now however, indicates that they will need to go further. Recommendations made in this report outline the need for them to reduce point source phosphorus loads entering the Wareham Channel by c30% (c3 tonnes OP/yr). In addition to this, all of the macroalgae-modelling scenarios show the discharge from Poole STW is having a significant impact on Holes Bay and the wider

catchment, as a result of the proportionately high nutrient load during spring and summer. To meet the conservation objectives it will be necessary for effluent from Poole STW to be discharged out of the catchment (to a location that would not cause harm to the environment or humans) or treatment levels on the site should be increased to c50% BAT for N and c10% BAT for P. The final permit conditions should be determined through further refined modelling and investigations proposed in PR19. Option appraisal also indicate that it will also be necessary to implement alterative diffuse mitigation options, such as wetland systems to remove sufficient N & P to meet conservation objectives. Currently c50 ha of wetland are currently planned, however approximately 250- 300 ha of specifically designed wetland system are likely to be required to improve surface water quality before entering Poole Harbour. This will reduce macroalgae densities and reduce the future risk of harm to venerable habitats such seagrasses beds and saltmarshes. The timing for the implementation of these measures will be subject to DEFRA guidance, however it would be recommended that water company investigations are undertaken in PR19, together with tightening of certain permits, already planned for and any major infrastructure improvements are made under PR24, AMP8. The timing to implement farm measures, will again be subject to the resource required. Field measures to reduce leaching and soil erosion such as a policy of no bare land by growing cover crops, can be implemented rapidly, in the next growing season. Measures that might require capital improvements and or significant financial investment might be implemented following a similar planning cycle as water companies, 2020-25 and major infrastructure improvements 2025-30.

1.0 Introduction. In 2013, the Environment Agency and Natural England produced a “Strategy for managing Nitrogen in the Poole Harbour Catchment to 2035” (NMP). This document outlined the measures that should be put in place to meet favourable condition of the Poole Harbour Special Protection Area and where technically feasible, GOOD status by 2027 under the Water Framework Directive. Key recommendations from this document were to bring nitrogen entering the harbour from non-marine sources down to c1732 tonnes N/yr. This were to be achieved through:

 Farmers to bring diffuse agricultural nitrogen losses from arable and managed grassland (based on 2010 land use) down to around 1180 tonnes/N/yr or c24kg/ha from high input land or c18 kg/ha from all rural land uses.  New development should not result in a net increase in nitrogen loads (achieved through water companies removing c75% increased load from growth and Local Authorities offsetting c25% load from growth). Since this, time both organisations have been working with local authorities, Wessex Water and farmers and their representatives to implement this strategy and these requirements. In 2015 the World Wildlife Fund UK, the Angling Trust and Fish Legal undertook a Judicial Review (JR) against the Secretary of State for the Environment, Food and Rural Affairs and the Environment Agency (EA). It was based on the perceived non-consideration of Water Protection Zones (WPZs), to deliver measures to tackle diffuse water pollution impacting on water-dependent Natura 2000 (N2K) sites. As a result of the JR a legally binding Consent Order (CO) was agreed between the parties. This requires the EA, working with Natural England (NE), to evaluate whether the existing measures and mechanisms to tackle pollution will lead to the improvements in water quality necessary to meet the conservation objectives for each N2K site. This document, represents this review for the Poole Harbour catchment.

2.0 Background 2.1 Conservation objectives Poole Harbour is a designated ‘transitional water body’ and ‘special protected area’ under the Water Framework Directive. The intertidal habitats and coastal waters of Poole Harbour are of international nature conservation importance. As part of the Conservation of Habitats and Species Regulations 2017 and Article 6(3) of the Habitats Directive, Poole Harbour need to be comply with specific Conservation Objectives. These are:

To ensure that, subject to natural change, the integrity of the site is maintained or restored as appropriate, and that the site contributes to achieving the aims of the Wild Birds Directive, by maintaining or restoring: The extent and distribution of the habitats of the qualifying features The structure and function of the habitats of the qualifying features The supporting processes on which the habitats of the qualifying features rely The population of each of the qualifying features, and, The distribution of the qualifying features within the site.

Formal advice on how to further the conservation objectives is provided under the Habitats Regulations as Supplementary Advice on conserving and restoring the site features can be found on the following link: https://www.gov.uk/government/publications/marine-conservation-advice-for-special- protection-area-poole-harbour-uk9010111/poole-harbour-spa-site-information-draft.

Part of these objectives are to maintaining a healthy abundance of macroalgae within the Harbour, which is the focus of much of this work. Where the objectives are met, the site will be considered to exhibit a high degree of integrity and to be contributing to achieving the aims of the appropriate directives. Further details on the objectives can be found in the following web site:

http://publications.naturalengland.org.uk/publication/6625771074355200 2.2 Conservation Status of Poole Harbour Catchment The extent of macroalgae mats in Poole Harbour has increased since the 1980s. The smothering effect of excessive macroalgae growth is attributing to the pressures on the environment and ecology of Poole Harbour. These excessive growth reduces species diversity and reduces the invertebrate food supplies of native birds and fish species to an extent where the Harbour is not meeting its conservation objectives. Under WFD assessment methods the harbour has been at moderate status for opportunistic macroalgae in every assessment since 2009. UK TAG provides guidance on methodology to achieve WFD status on a waterbody scale and Protected Area status at a sub waterbody scale. Using the UK TAG guidance (in 2017) six major areas of the harbour are classified as unfavourable (declining) condition, with Holes Bay, Arne (including Wych Channel and Wareham Channel), Ower Bay and Newton Bay. The assessment also shows there are no recovering areas, and that Salterns area and Green island showing as at risk. 2.3 Measures put under Nutrient Management Plan to achieve conservation objectives. The NMP published in 2013, identifies an ‘initial’ target load for dissolved inorganic nitrogen for the harbour that were thought necessary to achieve the favourable condition. This was set as 1730 tonnes per annum, from all catchment sources, excluding marine inputs. 1730 tonnes/N/yr was the nutrient load estimated to be entering the harbour in the early 1980s at a point just prior to excessive macroalgae growth being observed to extend from Holes Bay to the outer harbour. The NMP estimated that nitrogen loads had risen from around 1730 tonnes N/yr to around 2100 in 2010-11. It then forecast that these loads would further rise and stabilise at around 2300 tonnes/ N/yr if land use did not change from 2010 and including predicted growth to 2035 (and assuming discharge quality remained at 2010-11 levels). The NMP did not set a target for phosphorus. Recent work, completed since the NMP indicates that that loading in the 1980s may not represent the conservation objective target on nutrient status and further modelling has been carried out to determine what level of Nitrogen/Phosphorus would actually result in the required algal mat biomass/coverage throughout the SPA. A summary of this work can be found in Appendix 1 & 2.

3.0 Measures put in Place Since 2013 & Review of catchment Targets for the Purpose of the Consent Order Since the publication of the NMP in June 2013 the Environment Agency and its partners, have continued to implement the recommendations of the plan. The EA have also continued to monitor water quality [both river estuary and Sewage Treatment Works (STW)] and macroalgae densities across the harbour. In 2015 an updated agricultural census was undertaken and data from this has been used to assess the changes in agricultural practices from 2010-2015. Water company periodic review has also been ongoing identifying further measures that should be put in place under PR19, AMP7. Water companies have also been delivering requirement of Asset Management Planning Cycle 6 (AMP6). 3.1 Conservation Objective Targets Since publishing the NMP, advice on our interpretation of conservation objectives and standards used for the macroalgae abundance, have also been updated. These have been based on emerging scientific evidence. The primary conclusions from this are that:

- a lower average modelled biomass of

- a wet weight macroalgae biomass of 1.0 kg/m2 on suitable intertidal habitat should be used as a threshold value in, for example, assessing field data, as the point at or above which significant harmful effects on habitat biota are likely to occur.

This is a reduction from the value used in the NMP to describe when partial success of the NMP will be observed (NMP Section 1.2). A point at which:

- the extent of thick algal mats (> 2kg/m) is limited to <5% across Poole Harbour as a whole, and < 10% cover of any individual mudflat. This revised targets used a much wider base of monitoring information and has resulted in a shift from predominantly favourable and recovering condition to predominantly unfavourable, no change and declining condition (See Figure 1).

Exec Figure 1. Condition of Poole Harbour SSSI, SPA and Ramsar site intertidal assessment units, 2017 (Source Natural England)

Emerging research on estuarine eutrophication is also suggesting phosphorus reduction could also play a role in reducing eutrophication. Modelling of Poole Harbour’s water environment corroborates this, suggesting both phosphorus and nitrogen are fundamental in controlling macroalgae growth (Appendix 1 & 2). 3.2 Measures implemented or proposed to be implemented since 2013 Measures under current Asset Management Planning cycle 6 (AMP6) and future planning cycles (AMP7) at sewage treatment works have been confirmed with phosphorus loads being reduce at Maiden Newton STW, Cerne Abbas STW, Corfe Castle STW, Piddlehinton STW and Dorchester STW and N limitation at Wareham STW; due for completion between 2020 and 2025. Wessex Water have also introduced a scheme to help reduce diffuse nitrogen loads by 40 t/annum N loadings to offset Dorchester STW and future growth under AMP6. They also propose under AMP7 to investigate the impact of Poole STW on Holes Bay and the wider catchment and undertake options appraisal for mitigating any impacts Final wording for this will be informed by Consent Order work. Finally, ADAS Ltd were commissioned in 2017 to update our understanding of diffuse agricultural N & P inputs to the catchment, using the Farmscoper (v4) modelling tool (Appendix 6). To do this they have reviewed 2010 and 2015 agricultural census data and modelled the change in nutrient loading and loss that is likely to have occurred from farm engagement and implementation of measures. Some of the key land use change that are recorded to have occurred from 2010 to 2015 appears to be:

 Increase in woodland  Decrease in arable- other (non cereals)  Increase in grassland (and dairy cattle)  Increase in sheep  Increase in Poultry

3.3 NMP reduction strategy In the 2013, the NMP calculated spatially 73% of the nitrogen load was calculated to enter the harbour from inflowing rivers. Nearly 8% was from discharges direct into the harbour, mainly sewage treatment works (STWs). Agriculture was calculated to contribute about 84% of the nitrogen load from non-marine sources. The 2013 NMP identifies a strategy to delivering favourable status and water quality objectives. This includes:

 reduction diffuse agricultural loads to <1189 tonnes/yr [and average leaching not to exceed c24kg/N/ha across arable and managed grassland, or the equivalent of c18.3 kg/N/ha/yr as an average across all agricultural holdings (based on 2010 census data)]  Adopting a standstill approach from development growth whereby any additional nutrient load (forecast to equate to c40 tonnes/yr by 2035) is removed or offset.

There is an emphasis on:

 Farmers maximising soil and nutrient management efficiencies to achieve catchment targets, improve farm practices and the environment.  Partners provide prioritised agricultural advice through single point of contact (primary catchment contact), focusing advice in land areas and activities that present the highest potential risk and greatest environmental gain.  Advisers help farmers to understand how soil and nutrient management efficiencies can be improved and the environmental risk of not doing so.  Advisers agree with farmer’s further measures that should be put in place to ensure current and future practices do not cause pollution.  Partner seek farmers to implement measures voluntarily, signposting funding opportunities.  Where farmers will not engage or implement required measures, Environment Agency will undertake compliance visit to assess farm risk. Continued non engagement may result in EA using regulatory tools/powers to ensure farmers do not cause pollution.

4.0 Mechanisms in place to deliver catchment objectives & Effectiveness of these measures.

4.1 Mechanisms and measures put in place to deliver catchment objectives The NMP proposed that the EA and NE would initially work with farmers to try and achieved the diffuse load reduction on voluntary basis and would review the success in delivering this in 2019-20 (NMP Section 5.5). A plan was agreed to deliver the objectives “Diffuse Pollution Plan for Agriculture” and the EA and NE agreed a position statement with the National Farmers Union (NFU) and Country Landowners Association (CLA) outlining that farmers should implement “all reasonable measure” to maximise soil and nutrient management efficiencies to achieve these objectives. Details relating to this can be found in: http://webarchive.nationalarchives.gov.uk/20140328091437/http://www.environment- agency.gov.uk/research/library/publications/148450.aspx The diffuse pollution plan outlined how partner organisations would work to help inform and assist farmers to achieve these objectives. Signposting Catchment Sensitive Farming, Environmental Stewardship schemes (the latter replaced by a new Countryside Stewardship

scheme from 2015) and Wessex Water’s Catchment Management schemes & support as appropriate. The primary means of advice came through Government assisted support:

- Catchment Sensitive Farming (CSF). - Environmental Stewardship (ES - replaced by Countryside Stewardship from 2015) About 75% of the agricultural area is covered by ES agreements. This area is expected to decline as agreements expire and fewer holdings enter CS agreements. CSF has engaged holdings covering about 60% of the agricultural area, advising them on suitable measures and helped addressed many issues through uptake of Agri-environment options. This has substantially increased the uptake rates of mitigation measures from the background situation with regulatory requirements, but implementation remains below 50% for nearly all measures. Water company catchment management schemes also operates voluntary initiatives with farmers which are regulated through the Periodic Review process and AMP 6 and proposed AMP7: - Catchment management nitrogen reduction in groundwater safeguard zones mainly on the chalkland geology; - A nitrate offsetting scheme outside the chalklands that offsets nitrogen removal at Dorchester STW of 40 tonnes N/yr, the largest STW discharging to the catchment river system. This scheme includes use of a ‘reverse auction’ (EnTrade) with farmers bidding to reduce nitrogen leaching through planting winter cover crops or land use change on arable land. - Included in PR19 is a requirement for Wessex water to better understand the contribution of N and P from Poole STW on the harbour, investigate the potential for tightening permits and relocating the discharge. It is also required to establish the load contribution from water company assets (e.g. sewage works, foul sewer overflows and surface water sewers) that discharge to Holes Bay and its landward catchment area and undertake options appraisal to identify the most effective suite of measures that would reduce and/or offset the impact of these assets.

Current P limit New P limit Current DWF Completion date mg/L m2/day

Maiden Newton STW None 1 318 April 2020

Corfe Castle STW None 1.3 370 December 2021

PiddleHinton STW None 4 295 April 2025

Dorchester 1 0.7 9450 April 2025

Cerne Abbas STW None 0.8 159 December 2021

Wareham 15 mg/l N 2502 December 2021

River restoration schemes, enhancing river and riparian habitat to more natural structural diversity can increase de-nitrification in surface water drainage and river flow. There are two schemes that operate in parts of the catchment:

- River Frome SSSI rehabilitation plan. A long-term initiative, led and funded by EA, to restore the morphology of the River Frome SSSI to favourable condition. - Dorset Wild Rivers. A long-term initiative by the Dorset Wildlife Trust, funded by the Water Company and EA, centred on enhancement works along mostly smaller watercourses. Poole Harbour Catchment Initiative (Catchment Based Approach) hosted by Wessex Water also brought together catchment stakeholders in a Delivery Group and farming interests in a Farmers Group. Through this initiative EA, NE, CSF and the water company work in synergy in providing advice to farmers, focussing on the farms that present the highest potential diffuse pollution risks and working with them to identify how they can reduce these risks and meet the catchment targets. Where appropriate, modelling tools are used to assist farmers in understanding the impact their land use practices are having, and identify through modelling the most efficient measures to implement to reduce diffuse pollution. The majority of the catchment is also covered by Nitrate vulnerable zones (NVZs) and has resulted in a high level of change to farm management since its inception. This has resulted in an overall reduction in nitrate leaching, modelled by ADAS to be around 5% for N and ~10% for P, when averaged across the NVZs. It is also recognised however that the implementation of NVZ rules are only the starting point and farming may continue to cause pollution if they follow the basic NVZ requirements. In 2 April 2018 New Farming Rules for Water were introduced to help protect water quality, by standardising good farm practices that many are already performing and offering a new approach to regulation. Work completed by ADAS on the Poole Harbour catchment suggest that these rules will result in a 1% reduction in N and a 3% reduction in P. For a period of 2-3 years the Environment Agency utilized some of its Water Framework Directive Funding to supplement existing CSF and Water Company agricultural advice across the catchment with further agronomists. These contracts were delivered by ADAS and FWAG-SW.

5.0 Updated Evidence & Catchment Objectives 5.1 Source Apportionment & Nutrient reduction from the current strategy The current and forecast future nutrient losses from agricultural land holdings included in 2010 & 2015 Census Data (this is c75% rural land use/holdings) were calculated by ADAS using the Farmscoper model at a catchment scale. Results of this are summarised in Appendix 3 and Appendix 6 and can be found in detail as an Annex to this document. This work calculated that the implementation of the new farming rules for water together with AgriEnvironmental schemes (CSF, Water company catchment management schemes, environmental stewardship) is predicted to reduce nitrogen losses from around 1797 tonnes to around 1679 tonnes (c120 tonnes reduction). If Environmental Agri Schemes were no longer in place, the reduction would only be around 21 tonnes N and c1 tonne TP, primarily based on the new farming rules (Scenario 1; Table 5.1:1 and Appendix 6).

Table 5.1:1 Diffuse Nitrogen and Total Phosphorus Loads predicted by ADAS Farmscoper modelling.

The impact of river restoration schemes on nitrogen reduction is not known but at a catchment scale is likely to be small.

Total Nitrogen loads that are estimated to enter Poole Harbour catchment based on current land use and discharges (2013-17) are around:

 c2300 tonnes N/yr  c51 tonnes Orthophosphorus  c71 tonnes Total Phosphorus (Appendix 3 & 4). Of the phosphorus loads around 27 tonnes TP (around 18 tonnes Orthophosphorus using ratio of 0.65 OP:TP) are likely to result from agriculture once new farming rules have been put in place and assuming environmental stewardship continues (38% of p load) can be accounted for from land holdings reported in Census. Further losses will come from other rural land uses, urban and point sources. The proportion of diffuse nitrogen and phosphorus coming from each agricultural land use are detailed in Figure 5:3a & b. Figure 5:1 Nitrogen Source Apportionment for Poole Harbour Catchment (from Kite & Nicholson 2018; Appendix 3).

Figure 5:2 Estimated Direct and Indirect Input of Total Phosphorus and Orthophosphorus Entering the Poole Harbour Catchment Based on 2013-17 river water quality, Long Term Average Flows (1990-2017) and STW loads and concentrations 205-2017). Note river inputs include phosphorus from natural, diffuse and point source phosphorus inputs (from Bryan 2018 Appendix 4).

Figure 5:3: Agricultural Nitrogen & Total Phosphorus Sources Apportionment of Agricultural Land inputs (tonnes/yr) based on 2015 Census data and c75% rural land use a)

Despite a reduction in nutrient load predicted from agriculture, overall loads that are forecast to enter Poole Harbour from current land use and points sources, remain significant short of achieving 1730 tonnes N/yr NMP targets and diffuse agricultural target of c1200 tonnes N/yr (NMP Section3.1 Table .1:1). No target in the NMP was set for phosphorus entering the harbour.

Due to updated evidence used by the UK TAG guidance and tightening of the macroalgae targets, macroalgae-modelling updates, poor uptake of measures, inputs from STW the NMP strategy will fail to meet the conservation objective

Re-assessment of the N loads entering the harbour are therefore in agreement with those given in the NMP, P loads have also been calculated. Any future offsetting will need to be calculated from a baseline of – N loads of c2300 tonnes N/yr; and c51.2 tonnes OP or 71 tonnes TP (Appendix 4). Actual nitrate and phosphate loads are however likely to be higher if a flow apportioned approach were taken accounting for nutrient losses at high flows (Bower 2009).

Any future offsetting will need to be calculated from a baseline of – N loads of c2300 tonnes N/yr; and c51 tonnes OP/yr or 71 tonnes TP/yr

6.0 Macroalgae Modelling: Current and Future Scenarios 6.1 Macro-algae densities modelled from 2010-11, 2013-17 and NMP Scenarios. Varying models were used to assess the likely change in water quality and ultimately macroalgae growth that would result within the harbour from current and future management scenarios. An outline of the approach is illustrated in Figure 5:4.

Figure 5:1 Approach taken for modelling the macroalgae growth in the harbour. The first part of the approach is to calculate the nitrogen and phosphorus entering the harbour from river sources (River Frome, Piddle, Sherford, Corfe and other minor streams) and point sources directly discharges to the harbour. These loads were split, according to their discharge point, either through the Wareham Channel, Holes Bay, or direct discharges to the Outer Harbour (Figure 6:1).

Figure 6:1 Location of Differing “Boxes” modelled in CPM model & Contributing catchments

Three baseline models that were run are outlined below and in detail in Table 6:1.

 Nutrient loading entering Poole Harbour in 2010-11 period  Nutrient loading entering Poole Harbour in 2013-17 period  Nutrient loading that would enter the harbour once NMP measures had been put in place and 1730 tonnes N/yr nitrate target had been delivered (based on 2010-11 scenario). The macroalgae density forecast to be produced as a result of these nutrient loads [Dissolved Inorganic Nitrogen (DAIN) & Orthophosphorus] was then modelled using a combined phytoplankton Macroalgae model (CPM) developed by CEFAS and the Environment Agency (Appendix 1 & 2). Taking a conservative approach, as typically adopted by Environment Agency SAGIS- SIMCAT water quality models, the nutrients input included within the CPM model was a combination of DAIN, and fluvial Orthophosphorus (OP) and sewage treatment (STW) total phosphorus (TP). As outlined in Annex 3, the ratio of OP:TP for Poole, Wareham and Lytchett STW (the three main STW directly discharging to the harbour) is 0.81, 0.90 & 0.85. This means the maximum over estimate of OP is c19% using this approach. The results are conservative or precautionary, in that the overall STW OP will be slightly lower than is included in the model and therefore the macroalgae densities that results from each scenario are likely to be slightly lower than is forecast.

A precautionary approach has been adopted in forecasting macroalgae density that will result from water quality and management scenarios as a result of using STW Total Phosphorus concentrations rather than Orthophosphorus.

The results from these initial baseline model runs are presented in Table 6:2. These have been colour coded so where each model box meets the macroalgae modelling target of <500g/m2 or exceed them but are below the threshold value of 1kg/ m2 or exceed this. These results show that both 2010-11, 2013-17 and NMP scenarios are modelled to exceed the modelling target.

6.2: Future Water Quality Targets required to meet model macroalgae density and threshold density targets. As the CPM model forecast that the recommendations of the NMP, if fully adopted would still not meet the updated targets, further scenarios have been run to identify the nitrogen and phosphorus reductions and loading that would be required to meet modelled macroalgae targets and threshold target densities. These build on the NMP baseline case (case 1a) and are presented in Case 5a-5l. The description of each scenario are summarised in Table 6:1 and results are presented in 6:2, 6:3. A significant number of earlier model runs had been undertaken to build up this list of case examples. The basis for the final scenarios/cases are described in Appendix 6. In undertaking this work, it was identified that the CPM model does not realistically represent all the processes taking place in the Wareham Channel, as even with very low levels of DAIN and P, the modelling target was not met. It is thought therefore that other factors such as water depth, salinity, available intertidal area, wet environment, sedimentation and light penetration are not adequately represented in the model. The modelling work has therefore been focused on trying to achieve the 500 g/m2 target in the Outer Harbour and Holes bay. Further refinement of the CPM model may ultimately be required to ensure any measures put in place to deliver favourable condition across Holes Bay and the Outer Harbour, will also deliver this status across the Wareham Channel. This will require further funding and time.

Further model refinement may be required in the future to try and better represent all the processes occurring in this part of the harbour.

Table 6:1 Outline of the most relevant cases considered.

Case ID Description 2010-11 Loading, Note: Poole operating at 7.15mg/l. P Baseline set as 2013-17 using LTA flow- no measures + Holton Heath (now redundant) 2013-17 loading: 2013-2017 flow and WQ; All STW direct discharges at 2015-17 flow and load: Note: 2013- 17 was wetter than average and so river flows are higher 1 NMP Objectives Deliver: Macroalgae density when achieving NMP target of 1730 tonnes of N per annum: Note point source loading 328 tonnes, including c32 tonnes for growth (added to Poole STW; baseline) The figure of 1730 tonnes was taken from the NMP &1.34 tonnes P from growth of 20430 people discharging 1mg/l at Poole STW 2 NMP + Poole STW removed: As case 1 + Removing N and P loading from the Poole East STW from Holes Bay (assuming Poole STW discharge is piped out to sea or to different catchment). 3 NMP+ all STW @ BAT for N: As case 1 + Model based on reducing all STW discharges to 10mg/L (BAT) of N with exception of Poole which is maintained at 7.15 mg/l N. including growth 5a Wareham Channel N load required to deliver targets based on scenario 2: Poole: Poole STW discharges out of catchment- N Iterate at Wareham to achieve 500g in Poole Outer (All main rivers N inflow assumed to enter Wareham channel) updated LTA Flow, 5b Wareham Channel N load following improved treatment at Poole STW : Poole STW at baseline flow, 25% BAT- N only – N Iterate at Wareham to achieve 500g in Poole Outer (STW as 2013-17). Corfe P entering outer channel , Corfe N assumed to enter Wareham Channel (so total N iterated) no other measures; updated LTA river Flow 5c Wareham Channel N load following Improved treatment at Poole STW: Poole STW at baseline flows and 50% BAT - N only– N Iterate at Wareham to achieve 500g in Poole Outer (STW as 2013-17). Corfe P entering outer channel , Corfe N assumed to enter Wareham Channel no other measures; updated LTA Flow 5d Wareham Channel N load required to deliver targets: Poole STW discharged out of catchment & 20% P reduction: As 5a Poole STW discharges out of catchment P decrease by 20%: Wareham Chanel Iterate for N

to achieve 500g in Poole Outer (STW as 2013-17). Corfe P entering outer channel , Corfe N assumed to enter Wareham Channel no other measures; updated LTA Flow 5e N & P loads required to meet target when Poole STW discharge removed from harbour. As 5a Poole STW discharges out of catchment. If P is still limiting No Poole P decrease outer harbour P by 30% and iterate for P in Wareham Channel: Wareham Chanel also Iterated for N to updated LTA Flow achieve 500g in Poole Outer (STW as 2013-17). Corfe P entering outer channel , N assumed Wareham Channel no other measures; updated LTA Flow 5f N loads required in Wareham Channel when P reduced by 30% & Poole STW treatment improved: As 5c Poole STW at baseline flows, N at 50% BAT, Poole STW P reduced by 30% (P @ 70% BAT), P reduction of 30% across the catchment Iterate to achieve 500g in Poole Outer (STW as 2013-17). Corfe P entering outer channel , Corfe N assumed entering Wareham Channel no other measures; updated LTA Flow 5g N loads required in Wareham Channel when P reduced by 20% & Poole STW treatment improved: As 5f Poole STW at baseline flows, N at 50% BAT, But Poole STW P reduced to 10% BAT) discharging in holes bay, P reduction of 20% across the catchment Iterate to achieve 500g in Poole Outer ((STW as 2013-17). Corfe P entering outer channel , N assumed Wareham Channel no other measures; updated LTA Flow 5h N loads required in Wareham Channel when P reduced by 20% & Poole STW treatment improved Based on 2013-17: Updated river and STW flows 2013-17 + Corfe P entering outer box As 5f Poole N at 50% BAT, But Poole STW P reduced to 10% BAT) discharging in holes bay, P reduction of 20% across the catchment Iterate to achieve 500g in Poole Outer (All main rivers N inflow assumed to enter Wareham channel) 5i N loads required in Wareham Channel when P reduced by 30% & Poole STW treatment improved Based on 2013-17: Updated river and STW flows 2013-17 + Corfe P entering outer box As 5f Poole N at 50% BAT, But Poole STW P reduced to 10% BAT) discharging in holes bay, P reduction of 30% across the catchment Iterate to achieve 500g in Poole Outer (All main rivers N inflow assumed to enter Wareham channel) 5j N loads required in Wareham Channel when P reduced by 20% & Poole STW treatment improved but full permit uptake: Based on 2013-17:As 5h but Poole STW @ full permit uptake 5k Phosphate loads required in Wareham Channel when N at NMP target & Poole STW treatment in place: N @NMP, ALL STW @ 2010/11 loads N (except Poole @ 50% BAT for N and 10% BAT for P & Studland and Brownsea Island STW operating at 2mg/l P) , River flows at Long Term Average + , Corfe river P reduced by 30%& N reduced in Corfe by 20%; iterate for P 5l Phosphate loads required in Wareham Channel when N at NMP target & Poole STW discharged out of catchment. N @NMP minus Poole STW (c100 tonnes), Studland and Brownsea Island STW operating at 2mg/l P, River flows at Long Term Average flow, STW @2015-17, Corfe river P reduced by 30% & Corfe N reduced by 20%) ; iterate for P 9 Measures applied through NMP + AMP6 + 50% * best available technology (BAT) for Poole, Wareham, Dorchester and Lytchett, Blackheath and Wool (5mg/l N; No Dorchester offsetting). Poole STW P at 205- 17(Case 1 + Case 8 + BAT) 10 Measures applied through NMP + AMP6 + Poole STW Out of catchment + 50% * best available technology (BAT) for Wareham, Dorchester, Lytchett, Blackheath and Wool STW (5mg/l N; No Dorchester offsetting). (Case 1 + Case 8 + BAT)

Table 6:2: Option Appraisal to Achieve 0.5kgm2 (500g/m2) Maximum Macroalgae Density. Nutrient Loading Modelled (kg) and Macroalgae density in each box that result from this (g/m2)

Predicted macroalgae Density Total P Total N Phosphate Loading (tonnes/yr) Nitrate Loading (tonnes/yr) (g/m2) (tonnes/yr) (tonnes/yr) Outer Holes Outer Holes Outer Holes Case Wareham Wareham Wareham System System Harbour Bay Harbour Bay Harbour Bay 2010-2011 2.59 14.5 23.9 99.7 109 2033 500-1000 >1000 >1000 41.0 2242 2013-2017 3.18 31.8 24.3 81.2 142 2028 >1000 >1000 >1000 59.4 2252 1 2.59 15.8 23.9 81.9 109 1539 >1000 >1000 >1000 42.4 1730 2 2.59 0.09 23.9 81.9 9.2 1539 500-1000 <500 >1000 26.6 1631 3 2.59 15.8 23.9 80.0 109 1389 >1000 >1000 >1000 42.4 1578 5A 2.59 0.09 23.6 32.2 9.2 780 <500 <500 >1000 26.3 821 5B 2.59 31.8 23.6 32.2 44.0 883 <500 <500 >1000 58.1 959 5C 2.59 31.8 23.6 32.2 78.8 862 <500 <500 >1000 58.1 973 5D 2.21 0.07 20.5 32.2 9.2 872 <500 <500 >1000 22.8 914 5E 2.02 0.06 18.0 32.2 9.2 2053 <500 <500 >1000 20.1 2094 5F 2.02 9.81 18.9 32.2 78.8 770 <500 500-1000 >1000 30.8 881 5G 2.21 1.46 20.5 32.2 78.8 821 <500 <500 >1000 24.2 932 5H 2.80 1.63 21.1 32.2 86.5 790 <500 <500 >1000 25.5 909 5I 2.61 1.63 19.4 32.2 86.5 872 <500 <500 >1000 23.7 991 5J 2.61 1.83 19.4 32.2 96.3 872 <500 <500 >1000 23.9 1001 5K 1.58 1.46 18.5 72.1 78.8 1574 <500 <500 >1000 21.5 1725 5L 1.61 0.06 18.8 72.1 9.2 1551 <500 <500 >1000 20.4 1632 9 2.59 31.8 23.6 81.9 78.3 1373 >1000 500-1000 >1000 58.1 1533 10 2.59 0.09 23.6 81.9 8.7 1373 500-1000 <500 >1000 26.3 1463 11 1.23 13.4 21.5 81.9 134 2170 500-1000 >1000 >1000 36.2 2386 Numbers in red have been iterated using the model

Table 6:2 Summary of the results of each Nutrient & Macroalgae Model Case.

Required P discharge Required N discharge Targets Case ID compared to 2013-17 compared to 2013-17 Notes met OP&TP (59 tonnes) (2252tonnes N) 1 No 71% 77% Failed 2 Marginal 45% 72% Feasible 3 No 71% 70% Failed 5A Yes 45% 36% Unlikely to be feasible*1 5B Yes 98% 43% Unlikely to be feasible*1 5C Yes 98% 43% Unlikely to be feasible*1 5D Yes 39% 41% Unlikely to be feasible*1 5E Yes 34% 93% Feasible 5F Marginal 52% 39% Unlikely to be feasible*1 5G Yes 41% 41% Unlikely to be feasible*1 5H Yes 43% 40% Unlikely to be feasible*1 5I Yes 40% 44% Unlikely to be feasible*1 5J Yes 41% 44% Unlikely to be feasible*1 5K Yes 36% 77% Feasible 5L Yes 34% 72% Feasible 9 No 97% 68% Failed 10 Marginal 44% 65% Feasible 11 No 61% 106% Failed *1Unlikely to be acceptable or feasible as it is likely to require significant (>50%) arable and managed grassland reversion to natural/rough grazing. This is significantly beyond ADAS Scenario 6.

The model suggested that achieving the macroalgae objectives in Holes bay is likely, (subject to any re-calculation) to require point source measures that are beyond “fairshare” considering nutrient inputs to Poole Harbour catchment as a whole. This includes a reduction for both N and P at Poole East STW. This is a result of the proportionately high nutrient load entering holes bay from the STW compared with nutrient exchange from Wareham channel and the Outer Harbour, particularly during summer.

Macroalgae modelling also indicated that the outer harbour and Holes Bay were substantially P limed and so further reductions in P will achieve a significant reduction in macroalgae density (Appendix 1 & 2).

6.3 Modelled nutrient loading required to achieve macroalgae targets.

The principles considered in option appraisal include the following:  Technical feasibility  Socio-economic impacts  Cost/benefit  Proportionality (fair/share)

 Regulatory instrument (eg WPZ)  Delivery timescale

All case scenarios outlined in 5a-5l meet the water macroalgae density targets, as the nitrate, phosphorus or combination of N & P were iterated downwards until the model density targets were met. Case 5a-5d & 5f-5J focused on reducing nitrogen alone and outline that the targets can be met if nitrogen loads are reduced by 60-64% from around 2300 tonnes to <1000 tonnes N/yr and Poole STW either discharges out of catchment or treatment is significantly improved and N & P loads dramatically reduced. Cases 5e iterated nitrate and phosphorus and cases 5k and 5l, set the nitrate loads as those that would be delivered by the Nutrient Management Plan (c1730 tonnes) and then iterated P until targets are met. All three of these scenarios also assume Poole STW is discharged out of catchment or treatment is significantly improved. Cases 5a-5d & 5f-5J have however been discounted as despite them being technically feasible, they are likely to have a much greater socio economic impact on the catchment and greater cost. The basis for this conclusion are:

 c80-85% of the remaining nitrogen is from diffuse rural (and largely agricultural) sources, this would mean that the reduction would need to be delivered by these sectors, with diffuse agricultural nitrogen loads lowered below c700 tonnes N/yr.  ADAS Farmscoper modelling carried out as part of this project, identified that to reduce agricultural nitrate loads from around 1800 tonnes N/yr to 1200 tonnes (excluding alternative measures) would require all reasonable agricultural measures to be implemented as well as a c45% reversion from arable to low input grassland and a 24% reduction in stocking across the catchment (Section 6.5).  In order to meet the water quality target set out in case scenario 5a-5d & 5f-5J would require reducing diffuse agricultural loads again in the same order of magnitude. This would therefore require a significant proportion of all arable land to be reverted to low input (>50%) and a significant reduction in animal stocking across the catchment (>50%)  Alternative measure requiring a lower reduction in N have been identified (Cases 5e, 5k, 5l). Three modelling cases 5e, 5k and 5l (Table 6:2 – 6:3) were however considered to be potentially technically feasible and likely to have a lower socio economic impact and benefit. A summary of the nutrient loads required to deliver these targets and principles assumed in these modelling scenarios are outlined in the Table 6:4. Table 6:4 Comparison of suggested measures

Measure\Scenario run 5e 5k 5l Heading NMP + P NMP + Poole + Poole STW Discharged out of N at 50% BAT (5mg/l) Discharged out of catchment P at 10% BAT catchment (0.1mg/l) Brownsea & Studland*1

excluding STW direct discharging to harbour

Total N (tonnes/yr);

Recommendation: General Point Sources (STW) PS1. Nutrient loading from STW should not exceed 2010/11 (as outlined in NMP) to ensure there is no net increase in nutrient loads as a result of growth. It would be recommended that STW loads do not exceed c228. tonnes N/yr (2010-11 minus Poole STW N load). A provisional figure of c17.2 tonnes TP would be proposed (subject to further refinement).

PS2. STW Point Source Fairshare should be re-calculated based on final water quality targets. STW reductions should go beyond fairshare where this is required to deliver Habitats Directive obligations, such as macroalgae targets within Holes Bay. PS3. A c3 tonne P/yr reduction from STW in to the Wareham box to be implemented in PR24; in addition to Poole STW and other point source measures. This is to deliver an equivalent 30% reduction in STW input to rivers. PS4. Poole STW should either be discharged out of the catchment (to a location that would not present a risk to the environmental or humans), or should operate at c50% BAT for N and phosphate treatment installed and operated at c10-50% BAT for P (0.1-0.5mg/lP). The final permit conditions should be determined through further refined modelling and investigations proposed in PR19. PS5. Where not already met, Studland and Brownsea sewage discharge should be permitted to discharge a maximum concentration of c2mg/lP to reduce direct inputs to the outer harbour. Or the equivalent reduction in P delivered through other measures that will benefit the harbour. PS6. If diffuse fairshare cannot be reasonably delivered, consideration should be given to reducing nutrient loading entering Poole harbour from STW to123 tonnes N/yr & 12.8 tonnes P/yr, an equivalent that would be delivered by all STW operating at BAT for N and P and large STW (Poole, Wareham, Lytchett, Blackheath, Dorchester and Wool) operating at 50% BAT (5mg/l/N & 0.5mg/lP). PS7. Further refinement to the CPM model may be required to better understand macroalgae growth within the Wareham Channel.

6.5: Diffuse Measures to deliver macroalgae targets Results from the macroalgae modelling, Scenario 5k & 5l, indicate that the model targets can be achieved by reducing nitrate levels to those outlined in the NMP (c1730 tonnes N/yr) in combination with reducing phosphorus levels to 21.5 to 20.4 tonnes P/yr respectively (Table 6:2-6.4). To achieve this, diffuse loads should be reduced to the levels outlined in the NMP (

It would therefore be recommended that nitrate levels are lowered to NMP recommended levels of c1730 tonnes N/yr and phosphorus to c20-21.5 tonnes OP/yr & diffuse agricultural loads where technically feasible are reduced to c1200 tonnes N/yr.

Diffuse load reduction can be achieved by either reducing nutrient inputs or losses from soil zone and or the transport of nutrients to surface waters.

ADAS were commissioned to identify the measures that could be put in place to reduce diffuse agricultural nitrogen losses from the current forecast regulatory baseline of c1800 tonnes N/yr to 1200 tonnes N/yr (as recommended by the NMP). To do this, they used the Farmscoper modelling tool, and calculated the diffuse agricultural nutrient and suspended sediment losses from land holdings registered in the 2010 and 2015 agricultural census. This accounted for around 75% of rural land use and therefore does not account for all rural nutrient losses. Following the advice of agricultural groups in the area ADAS identified 6 scenarios and “bundles” of measures that could be implemented. The first represented the measures that are largely required under new farming rules. Scenario 2 focusing on reducing nutrient application and or measures to reduce nutrient leaching over winter. Scenarios 3-4 included other measures that farmers could implement. The Final 2 scenarios were focused on the measures that would be required to reduce nutrient losses further to achieve 1200 tonne N/yr target. They included reverting a proportion of arable land to low input grassland (Scenario 5) or reducing stocking densities (Scenario 6). The level of nutrient reduction achieved by each scenario is outlined in Table 6:5 and Figure 6:2 & 6.3 and further discusses in Appendix 3 and ADAS technical documents Appendix 6. As the agricultural phosphorus reductions delivered are Total Phosphorus, and a smaller Orthophosphorus loading will be achieved, the TP values have been adjusted using the average OP:TP ratio observed in the Frome and Piddle from 2013-2017 of 0.65 (Appendix 4).

Scenario 1 (Farming Rules for Water)  Use a fertiliser recommendation system  Integrate fertiliser and manure nutrient supply  Do not apply manufactured fertiliser to high-risk areas  Avoid spreading manufactured fertiliser to fields at high-risk times  Do not apply organic manures to high-risk areas  Site temporary solid manure heaps away from watercourses  Move feeders at regular intervals  Fence off rivers and streams from livestock

Scenario 2 (+Scenario 1)  Fertiliser spreader calibration  Use clover in place of fertiliser nitrogen  Establish cover crops in the autumn  Early establishment of crops in the autumn

Scenario 3 (+Scenario 1&2)  Reduce dietary N intake  Adopt reduced cultivation systems  Use manufactured fertiliser placement technologies  Increase the capacity of farm slurry stores to improve timing of slurry applications  Store solid manure heaps on an impermeable base and collect effluent  Use liquid/solid manure separation techniques  Construct bridges for livestock crossing rivers/streams

Scenario 4 (+Scenario 1&2&3)  Establish 6m wide riparian buffer strips

 Establish in-field buffer land/zero input margins on 3% of arable land  Allow grassland field drainage systems to degrade

Scenario 5  45% land reversion to low input pasture from arable farms

Scenario 6  35% reduction in stock numbers on livestock farms.

Table 6:5. Diffuse Load Reductions achieved by Farming Scenarios 1-6 modelled by ADAS using Farmscoper Tool (kg/N/yr & kg/TP/yr).

Note: 1: All nutrient reductions have assumed a 95% uptake of suggested measures, which is likely to require legislative intervention to implement. 2: TP benefits delivered by these scenarios have been adjusted using OP:TP ratio of 0.65 (Appendix 4).

Figure 6:2 Nitrate Reductions Delivered by Farmscoper Model Scenarios (ADAS March 2018)

reduction by scenario 1900 additional reduction by existing schemes 1800 143 21 remaining nitrate-N loss 97 1700 93 148

1600 35 34 24 23 23

1500 109

Ntonnes/yr - 1400

1,679 261

Nitrate 1,651 1300 1,594 1,570 1,548 1,462 1200

1100 1,201

1000 NVZ & Sc1 Rules for Sc2 Sc3 Sc4 Sc5 Sc6 background Water only

Figure 6:3 Total Phosphorus Reduction Achieved By Scenario 1-6.

6.5 Alternative Measures to Deliver Diffuse Pollution Reduction: Wetland Creation Alternative & potentially in combination measures are likely to be required to deliver water quality improvements across the Poole harbour catchment. Wetland creation may go some way as to removing nutrients from the Harbour. Natural England have looked at research to identify the potential nutrient reduction that might be achieved through wetland systems (Appendix 3). Based on published research, this work has identified that a nutrient reduction of between 500- 1000 kg/N/ ha of wetland could be delivered and c 20kg P/ha if sufficient river flow is diverted through a well-developed wetland system.

In assessing the effectiveness of wetland systems, an assumption has been made that each hectare of wetland will remove 750 kg/N & 20 kg/P. The benefits therefore for increase area of wetland are outlined in Figure 6:4.

Figure 6:4 Nutrient Offsetting estimated to be provided by Wetland Creation

Development of wetlands are likely to have many water quality and environmental benefits. They may however have some adverse impacts, such as potentially increasing evapotranspiration losses and reducing flow in rivers. Many of these issues could however be mitigated, such as installing wetland systems at the bottom or water courses. This might also maximise the potential for nutrient offsetting, but would reduce the length of fluvial water course that benefit from any water quality improvement.

Prior to installing any wetland further work will need to be undertaken, including opportunity mapping, detailed design and risk assessment to identify the impact they may have on the wider water environment. The cost benefit should also be assessed and suitable location identified to maximise the benefit and minimise the detrimental impacts. Funding for their installation may be sought through the new Water Environment Grant. Around 50ha of wetland are already being planned across the Poole Harbour catchment (Appendix 3).

6.6 Recommended in combination Measures to Deliver Water Quality Improvements Because of the challenging water quality targets, it will be necessary to implement in combination measures to deliver the catchment objectives. The approach taken in considering how these are put forward are detailed below and in Section 6:3 above:

1. Implement point source improvements required to deliver favourable condition, such as improvement in Holes Bay. 2. Implement wider point source improvement required to deliver favourable condition and equitable nutrient reduction to fluvial sources (considering also improvements made to date). 3. Implementing diffuse measures from the group that are least onerous and can be achieved without wholesale land reversion (diffuse measures 1). In order of preference this is considered to be ADAS scenarios 1, 2, 4, 3. 4. Implement alternative measures to the land area that may be reasonable, given opportunities across the catchment. 5. Implement measures that may require land reversion and wholesale land use change, potentially being more onerous: (ADAS Scenarios 5-6). Results of this are outlined in Table 6.6. Table 6.6a-c Measures Required To Deliver Case 5e, 5K & 5l a) Case 5e

b) Case 5K

c) Case 5L

These results show that all if the scenarios can be delivered by a combination of point source, diffuse source and alternative measures. The following recommendations can therefore be made regarding diffuse source reductions:

7.0 Mechanisms and timescales to Deliver Favourable Conservation Targets. Modelling shows that a significant reduction in N and P is required from diffuse and point sources to meet catchment water quality objectives. Recommendations outlined above identify the type of measure that could be put in place to deliver these water quality improvements. Mechanisms to deliver these objectives are considered in Section 7.1 & 7.2. 7.1 Point Source Mechanisms to Implement Measures Any point source improvements should be implemented through Asset Management Planning (AMP) and Periodic Review (PR) Processes. AMP6 includes schemes for Wessex Water to:

- Install P reductions at Maiden Newton, Cerne Abbas & Corfe Castle STW introducing a 1, 0.8 & 1.3 mg/l P limit respectively (AMP6). PR19 proposals schemes:

- Introduce P reductions at Piddlehinton STW to 4mg/l, further tightening Dorchester STW P limit to 0.7 mg/l (from 1mg/l). - Improve treatment at Wareham to reduce nitrate t. - investigate the impact of Poole STW on the water environment and undertakes an option appraisal to identify how any impacts might be mitigated - Implement P reductions at Dorchester, Maiden Newton &. PR 19 also includes improvements at Wareham STW. It would be recommended that these investigation are widened to identify how PS1-7 can be most effectively be delivered. These objectives may help to deliver the recommendations outlined in PS1, PS3, and PS5. Further investigations at Poole STW, currently proposed in PR19 should be shaped to help to inform the option appraisal required under recommendations PS4. Agreed findings from this work should be implemented in PR24, AMP8 from 2025-2030 (if it is not possible for it to be delivered before). Delivery of these recommendations may go beyond current understanding of fairshare in the catchment. These calculations should however be updated in light of the new water quality targets and where they do, government policy may need to be update to allow for water companies to be required to go beyond fairshare to meet Habitats Regulation objectives. Once these point source measures have been implemented, there will be an immediate reduction in nutrient loads entering rivers and estuaries. There may however be a delay in overall water quality in the harbour as nutrients from sediments are likely to continue to leach out and wider diffuse nutrients reduction may take longer to be realised.

7.2: Mechanisms to deliver diffuse pollution reductions and measures. 7.2:1 Current legal powers to prevent pollution Nitrate and Phosphorous are not hazardous pollutants and farmers (and other land holders, owners) have a legal obligation to ensure they do not cause of knowingly permit pollution to waters (Environmental Permitting Regulations (2010) Regulations 38(1)(a) and 12(1)(b)). Recommendations regarding the level of nutrients applied to land to achieve the best financial return for a farm business are outlined in DEFRA RB2094. However the split of organic and inorganic manure applied to achieve maximum productivity, need to be controlled to maintain compliance with Nitrate Regulations where a farm is within a Nitrate Vulnerable Zone and to ensure it does not result in damage to the Environment (COGAP) and or pollution.

The Nitrate Regulations set limitations on the amount of organic manures that can be spread through the year and timing of its application. Within NVZ  Farm limit of 170kg N/ha/year from livestock manures averaged over the total area of the farm.  Field limit of 250kg N/ha/year from livestock manures. These figures exclude the load deposited by animals whilst grazing.  Additional inorganic nitrogen can be applied in accordance to crop requirements outlined in RB2094 Outside NVZ  Field limit of 250kg N/ha/year from livestock manures. These figures exclude the load deposited by animals whilst grazing.  Additional inorganic nitrogen can be applied in accordance to crop requirements outlined in RB2094

Modelling work and field observations across the country and within Poole Harbour have shown that this alone is not sufficient to prevent pollution and nitrate applications at maximum rates detailed within the NR and recommended by RB209 may still result in pollution.

Where farmer’s use of N & P or farming practices result in pollution, the measures available to the Agency beyond Nitrate Vulnerable Zones for controlling nitrate inputs to groundwater are:  works notices under section 161A WRA 1991 and  Environmental Permitting Regulations (EPR) 2010 either prohibition notice or permitting.  Application for Water Protection Zone

7.2.2: Recommended diffuse pollution mechanism & measures Demonstrating or proving pollution is often difficult and time consuming. It would therefore be recommended that other approaches are used across the Poole Harbour catchment to ensure that land owners are meeting water quality objectives. ADAS modelled the uptake of diffuse measures required to bring diffuse agricultural nitrogen loads down to 1200 tonnes/N/yr in Scenarios 1-6 as having a 95% uptake rate. Evidence over the last few years, decades have shown that a voluntary uptake of measures is significantly below this figure and it is unlikely to be possible to achieve this level of uptake using a voluntary approach.

Measures that are implemented on a voluntary basis, may also take a significant amount of time and resource to implement and are often subject to rapid changes depending on farm economics. For example, the benefits delivered by environmental stewardship schemes are subject to funding and cycles. The benefits delivered by such schemes are often short term and can very rapidly be reversed when the schemes come to an end (Appendix 3). Also farming practices and cropping can also change rapidly, subject to national and international demand. In recent years the expansion of bio-digesters, has increase the demand for Maize and in many cases this may locally have resulted in an increased diffuse pollution. This may result from the often late cropping of maize, the difficulty in under sowing such crops and or inability/difficulty in establishing a cover crop following harvest. This means that fields where maize has been grown often remains bare over winter increasing the nutrient and soil erosion risk. Therefore to increase the confidence in diffuse pollution targets being delivered, it would be recommended that specific measures and or maximum leaching nitrate and phosphorus targets are given regulatory backing through a Water Protection Zone of other legal mechanisms/obligation. Where appropriate, this should be aligned with support and incentives to assist farmers in delivering these obligations (see 6.6). Where a leaching targets are set, it will also be necessary to develop the process & tools farmer, land owners and regulators use to assess their current and future compliance. Because of variability in climatic conditions, it may not be feasible for farmers to achieve a leaching target in every year. The approach should therefore consider their “typical” or “average” farming practices over an agreed period of time, such as over an average of 5 years, and ensure their land use practice meet these targets and do not cause pollution during average years. Some flexibility should also be given to deciding the measures that are put in place to achieve these leaching targets. However the widespread implementation of certain measures is likely to be fundamental to reducing diffuse pollution and as such farmers should be obliged to implement them where they are relevant to the farming system. Many of these are included in ADAS Scenarios 1-4 but are likely to include:

- Use of cover crops (so there is no bare land over winter) to reduce nutrient leaching and soil erosion. - Need for farmers to annually undertake nutrient planning to ensure application rates and practices each year are suitable for the typical yield each farm may achieve and on average will not result in nutrient leaching that exceed catchment leaching/water quality target (taking into account many factors including aerial deposition of N). - Manure and Fertilizer applicator calibration: to ensue manure and fertilizers are applied in accordance with nutrient planning. The timing that these measured and mechanisms are implement can also vary according to the amount of planning, preparation and infrastructure improvements required. Measures such as the need for fertiliser calibration, buffer strips and cover crops can be implemented within 1-2 years of any recommendations being agreed, such as in the next cropping year. Other measures that require capital improvements such as increasing slurry storage and bridge construction may require a longer period of time to be implemented, because of the investment required. A recommended schedule of any implementation will be provided in

final submission and with the measures needed to be consulted on. The timescales for implementation of measures requiring long term investment are likely to align with water company AMP cycles, with the first tranche being delivered by 2020, the next 2025 etc. Work highlighted by the ADAS report also shows that some measures need to be targeted and consideration to the farm type, business structure, soil type / geology need to be considered amongst other things.

Recommendation: Diffuse Measures DS1: Diffuse Phosphorus loads (OP) should be reduced by c30% to achieve macroalgae targets. DS2. Average phosphorus loads (point and diffuse) entering the harbour, calculated though annual average approach should be reduced to c20 tonnes OP/yr. DS3: Nitrate loads should be reduced to those outlined in the NMP c1730 tonnes/N/yr (before Poole STW is accounted for) c1630 tonnes/N/yr after. Diffuse Agricultural Nitrogen should be reduced to c1200 tonnes N/yr (achieved by agricultural measures Scenario 1-4 and potentially in combination measures such as wetland schemes). DS3: In alignment with the current NMP, land use activities across the Poole Harbour Catchment, including farms or specified “groups” of farm should not exceed a specified nitrate and phosphorus leaching target over a 5year period. This is provisionally set at 24kg/N/ha for high input agricultural areas or c18.4kg/ha for all rural land uses based on 2010 land use. This figures shall be refined subject to the agreement and development of “in combination” measures and further loads for phosphorous outlined in final recommendations. DS4: Significant nutrient loads enter the catchment through aerial deposition (c13 kg N/ha/yr). Farmers should incorporate these loads within their nutrient budgets & planning. This will reduce the amount of nitrate that will need to be spread to meet crop requirements and help therefore to stop over application & leaching of nutrients to ground. DS5: There should be a legal requirement to implement certain measures (appropriate to their farming practices) considered to be fundamental to achieving diffuse pollution reduction. They are likely to include key measures in ADAS Scenario 1 & 2 and in particular, mandatory use of cover crops to prevent land being left bare over winter, annual nutrient planning to ensure their average farm practices will not result in nutrient leaching that will exceed catchment targets, regular calibration of fertilizer application equipment and others. DS6. As under NVZ rules Farmers across Poole Harbour must maintain an annual record of their nutrient management plans and be able to demonstrate their plans and practices being implementing will not result in leaching and or soil and nutrient loss that exceed catchment targets on an average year. This will require existing nutrient planning tools to be further refined to have this functionality. DS7. In combination measures should be selected to deliver diffuse pollution reduction beyond Agricultural Scenarios 1-4. This may include the installation of >250 ha wetland (or alternative that are technically feasible and least onerous. DS8. Opportunity mapping should be finalised to identify where wetland could be created. These should be focused in areas that would result in the greatest water quality improvement with minimum environmental impact (such as on low river flows). Funding to develop these may be sought through new Water Environment Grants.

Recommendation: Mechanisms DM1. Water Protection Zones or other legal obligations should be set to ensure farmers or groups of farmer’s average nitrate and phosphorus leaching or losses do not exceed catchment targets (those required to ensure their average practices do not cause pollution). DM2. Farmers and land holders/owners should also be obliged to implement key measures, where relevant to their farming practices that are fundamental to achieving the diffuse pollution reduction required across the Poole Harbour Catchment. DM3. The Environment Agency and Natural England should set up a technical working group which will include technical representative from key stakeholders, including the farming community to refine these measures to achieve the water quality targets set out in this document DM4. Any point source improvements should be implemented through Asset Management Planning (AMP) and Periodic Review (PR) Processes

8.0 Stakeholders & Engagement A summary of the engagement undertaken to date is outlined below:

1. Based on a National template a bespoke key messages briefing note has been produced which included a Project plan and Engagement plan. 2. The Briefing note containing key messages, a proposed project plan and a Stakeholder engagement plan for the consent order work was circulated mid-2016 to the Poole Harbour Catchment initiative delivery group via Nicola Hopkins (Catchment coordinator). Some discussions about engagement process followed. This was updated in 06/17 and again later in 2017 as and when the timetable needed to be adjusted. 3. Project manager and Technical leads attended PHCI meeting in December 2016 to present the plan and some of the key issues and to ask for input notably and data they may hold or know of. 4. During 2016-17 some Farmer Group meetings attended by Doug Kite and Giles Bryan for general discussion and consult on potential options to include in the ADAS Farmscoper 1 contract 5. Mid December 2017 outputs from Farmscoper shared with Farmer group and PHCI and wider EA and NE for feedback on ADAS report outlining potential options to model. 6. A fact finding site visit to Poole Harbour catchment was made in Jan 2017 by Defra, NE, EA and NGO’s senior management to see the issues and discuss progress first hand. Various support materials were provided. 7. PHCI (Nicola Hopkins) periodically appraised of progress of work and discuss any issues. 8. During April key findings were shared with PHCI. 9. At the end of May 2018, further consultation of ADAS Farmscoper modelling will take place. 10. Informal discussions have taken place with Wessex Water and key recommendations from this report were shared in April early May. 11. Further plans to attend farming group meeting arranged by NFU and Catchment Co-ordinator.

Subject to DEFRA’s agreement and approval, it is proposed that the detail of how the high level recommendations outlined in this document are implemented, should be developed and refined over the forthcoming months. This should be developed in partnership/consultation with the appropriate stakeholders impacted. Water Company and farming community should put forward expert representatives who will work with the Environment Agency Natural England to develop these details. It would be advised that a further period of consultation of any recommendations should then follow.

9.0 Cost effectiveness Farmscoper modelling includes cost of each of the measures put forward. These findings are in ADAS “Poole Harbour Scenario Modelling” March 2018 (referenced in Appendix 3). Cost benefit and ecosystem service assessment of the proposals will follow DEFRA and partner comments on this report.

10.0 Recommendations

Recommendations have been made in this document and will not be repeated in detail here. A summary of the key findings of the work are however detailed below:

 Subject to the suitable mechanisms being put in place and where appropriate funding or support provided, Macroalgae targets are likely to be achievable across the Poole Harbour catchment, delivered through a combination of point, diffuse and additional measures.  Nitrogen loads entering the harbour from fluvial and point source discharges (excluding marine input) should be lowered to Nutrient Management Plan (2013) target of 1730 tonnes N/yr.  Phosphorus loads (OP) should be lowered to c20.5-21.5 tonnes OP/yr.  Sewage Treatment Works Orthophosphorus loads discharged and which enter the Wareham Harbour area should be reduced by c30% approximately 3 tonnes/OP/yr.  Effluent from Poole STW should either be discharged out of the catchment (to a location that would not present a risk to the environmental or humans), or should operate at c50% BAT for N and phosphate treatment installed and operated at c10-50% BAT for P (0.1- 0.5mg/lP). The final permit conditions should be determined through further refined modelling and investigations proposed in PR19.  Overall point source loads entering the harbour and considering growth should not exceed 2010-11, as delivered by the above measures.  Fluvial phosphate loading to the harbour should be reduced by 30% by a combination of further point source (outlined above) and diffuse pollution reductions.  Diffuse pollution leaching targets and measures have been recommended. These should be implemented across all rural land uses and farms / groups of farms to achieve a c30% reduction in phosphate and bringing nitrate losses from agricultural land to below 1200. An agreed modelling approach will need to be developed to enable farmers and landowners to calculate the N & P leaching that would typically result from their current and future land use practices and ensure these do not exceed leaching targets.  There should be a legal requirement for farmers and land holders to implement certain measures considered to be fundamental to achieving diffuse pollution reduction. These should be confirmed by a technical working group, including technical representative of farming community and in consultation with catchment stakeholders. These are likely to include key measures in ADAS Scenario 1 & 2 and in particular, mandatory use of cover crops, nutrient planning to model leaching from proposed cropping and management to ensure typical farming practices will not exceed leaching targets on an average year, calibration of fertilizer application equipment.  As under NVZ rules Farmers must maintain an annual record of their nutrient management plans and be able to demonstrate their plans and practices they are implementing will not

result in leaching and or soil and nutrient loss that exceed catchment targets on an average year.  Delivery of all diffuse nutrient reductions will be challenging but achieving diffuse nitrate reduction may be the most difficult. Modelling indicates that it will be necessary to implement additional measures such as wetlands creation to further offset nitrate and phosphate loads in the catchment and to achieve nitrate diffuse pollution targets. Modelling work indicate that implementation of c250-300 will be needed in additional to ADAS scenarios 1-4 to achieve water quality targets.  Point source improvement and diffuse phosphorous offsetting and the installation of wetland systems once developed will result in the most rapid reduction in input nutrient loads to the harbour. Measures that reduce nitrogen leaching to ground, will take longer to be delivered as c80% of the nutrient will get to the harbour through the groundwater pathway. This on average this may take 30-35 years.  Nitrate and phosphorus concentration within the harbour may remain high following input reductions as a result of leaching from sediment with the rivers and harbour system. It may take years or decades for these nutrients to be leached.  Whilst diffuse and point source measures are implemented and nutrient concentrations are gradually reduced in feeding and receiving water courses, it may be beneficial to mitigate the impact of macroalgae through macroalgae harvesting. It would be recommended that the approach to harvest alga are piloted to identify the approach that would result in the greatest environmental gain with least financial and environmental cost. Where this pilot identifies it is environmental and cost beneficial any such scheme might be scaled up.

References

1. Bryan etal, Strategy For Managing Nitrogen Across Poole Harbour Catchment to 2035. 2. Gooday etal March 2018; Poole Harbour Scenario Modelling 3. Gooday etal, November 2017 Poole Harbour Nitrogen Management Investigation. 4. Bowes, Smith & Neil ; The value of high-resolution nutrient monitoring: A case study of the River Frome, Dorset, UK: Journal of Hydrology 378 (2009) 82–96. 5. Ricardo Nov 2017; Poole Harbour Algal Harvesting Pilot Study. 6. Kite & Nicholson 2018 Background information for understanding the catchment situation on nitrogen nutrient enrichment in the Poole Harbour Natura 2000 site: Kite & Nicholson 2018 Error! Bookmark not defined. 7. Edwards 2018; Summary of Poole Harbour dynamic Combined Phytoplankton and Macroalgae (CPM) Modelling- Calibration Study. 8. James, Edward & Bryan 2018. Water Quality and Macroalgae Modelling of Poole Harbour: Estimated the required reduction in nutrient to achieve acceptable densities of Macroalgae; James, Edward & Bryan 2018. 9. Wessex Water, Wareham N Removal Challenge Paper (2017) 10. Wessex Water, Poole Harbour N Savings Estimate (Nov 2016)

Appendix 1 : Summary of Poole Harbour dynamic Combined Phytoplankton and Macroalgae (CPM) Modelling- Calibration Study. Edwards 2018

This annex can be found as a separate document

Appendix 2: Water Quality and Macroalgae Modelling of Poole Harbour: Estimated the required reduction in nutrient to achieve acceptable densities of Macroalgae; James, Edward & Bryan 2018.

This annex can be found as a separate document

Appendix 3: Background information for understanding the catchment situation on nitrogen nutrient enrichment in the Poole Harbour Natura 2000 site: Kite & Nicholson 2018

This annex can be found as a separate document

Appendix 4: Phosphorus Sources Across the Poole Harbour Catchment & Apportionment; Total Inorganic Phosphorus (TP) & Orthopho-phosphorus Bryan 2018.

This annex can be found as a separate document

Appendix 5; Trends in total oxidised nitrogen (TON) in surface waters in the Poole Harbour catchment, 1976 to 2016; Environment Agency Wessex Area Analysis and Reporting Team. Draft October 2016

Background The Environment Agency has monitored total oxidised nitrogen (TON) and/or nitrate concentrations in surface waters in the Poole Harbour catchment since the mid 1970’s. The monitoring frequency is variable across the period of record but is typically monthly. Trend analysis was undertaken on the TON record because at most sites it is more comprehensive than the nitrate record. Methodology Surface water monitoring sites in the Poole Harbour catchment were selected for trend analysis using the criteria that (i) the sites were currently (2016) monitored for nitrate or TON and ii) the length of the TON or nitrate record was at least 25 years. The locations of the 20 monitoring sites selected are shown in Figure 1. TON, nitrate and nitrite data for the period 01/01/1970 to 14/09/2016 were downloaded from WIMS using the SlimWims interface. Samples with the purpose codes UI and UF (i.e. pollution incident samples) were excluded from the data retrieval. Where possible, short gaps in the TON record were filled by summing corresponding nitrate and nitrite results. Nitrite results below the limit of detection were given a value of half the limit of detection in all calculations and nitrate results below the limit of detection were given a value of the limit of detection in all calculations. No outliers were excluded from the analysis. Trend analysis was undertaken using R (R Development Core Team, 2011) with the package rkt (Marchetto, 2012). The seasonal Kendall trend test (Hirsch et al., 1982) was used to test for statistically significant (p<0.05) monotonic upward or downward trend over the period of record. This non-parametric test is appropriate for monthly water quality time series that, as in this case, exhibit marked seasonality, and is applicable in the presence of missing values, outliers and values below the limit of detection. Month was used as the blocking variable (season) in the analysis. Where there was more than one record in a month the median value was used. The analysis was undertaken both with and without correction for serial correlation between months. The seasonal Kendall slope estimator was calculated to estimate the magnitude of the trend (i.e. concentration change per unit time) over the period of record. Results Scatterplots of TON against time with lowess (locally weighted scatterplot smoothing) lines for all 20 sites examined are shown in Figure 2. The plots indicate increasing trends in TON concentrations at most sites. However, these trends are not always linear over the entire period of record and concentrations appear to be stable or decreasing at some sites. The results of the seasonal Kendall trend tests are given in Table 1. Correction for serial correlation between months did not change any trends from significant to non-significant and

for clarity only the uncorrected two sided p values are presented. The tests confirm that there have been highly significant increases in TON over the period of record at most sites in the catchment. The exceptions to this are the Wraxhall Brook at Sandhills and Sherford River at King Bridge, both of which showed no significant upward or downward trend in TON, and the Corfe River at Corfe Castle which showed a significant decrease in TON. For those sites showing a significant increase in TON over the period of record, the slope value ranged from 0.02 to 0.13 mg/l-N/year with an average value of 0.07 mg/l-N/year. This equates to an increase of 2.8 mg/l N over 40 years (1976 to 2016). References Hirsch, R.M., Slack, J.R. and Smith, R.A. (1982) Techniques of trend analysis of monthly water quality data. Water Resources Research, 18, 107-121. Marchetto, A. (2012) rkt: Mann-Kendall test, Seasonal and Regional Kendall Tests. R package version 1.1. http://CRAN.R-project.org/package=rkt. R Development Core Team (2011). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. http://www.R-project.org/.

Figure 1. Map showing monitoring site locations and underlying geology. See Table 1 for site code index (needs geology key).

Figure 2. Scatter plots of TON against time with lowess fits. Note that the y-axis has been truncated at 12 mg/l for clarity. Table 1. Summary of seasonal Kendall trend tests for entire period of record. Underlined p values indicate no statistically significant trend.

Catchment Site code Site name Period of Years of SK slope p record data (mg/l- (two-sided) N/year)

Frome 50530197 River Frome at Maiden Newton 1976- 40 0.0300 0.0000 2016 50530138 River Frome at Notton 1976- 40 0.0455 0.0000 2016 50550158 River Frome at Bradford Peverell 1980- 36 0.0563 0.0000 2016 50570251 River Frome u/s Dorchester STW 1976- 40 0.0667 0.0000 2016 50550130 River Frome at Bockhampton 1976- 40 0.0846 0.0000 2016 50590188 River Frome at Wool Bridge 1976- 40 0.0688 0.0000 2016 50590127 River Frome at Holme Bridge 1986- 30 0.0558 0.0000 2016

50590907 River Win at Seven Stars 1980- 36 0.0464 0.0002 2016 50560120 South Winterbourne at Came 1980- 36 0.1268 0.0000 2016 50510309 Wraxall Brook at Sandhills 1981- 35 -0.0098 0.0504 2016 50550310 River Cerne at Charminster 1984- 32 0.0441 0.0000 2016 50550362 River Cerne at Nether Cerne 1976- 40 0.0473 0.0000 2016 50540108 Sydling Water at Grimstone 1980- 36 0.0880 0.0000 2016 50580145 Tadnoll Brook at Mill House 1978- 38 0.0469 0.0000 Nursery 2016

Piddle 50410164 River Piddle at Piddlehinton 1976- 40 0.1037 0.0000 2016 50450129 River Piddle at West Mills 1977- 39 0.0896 0.0000 2016 50440119 Bere Stream d/s Doddings 1989- 27 0.0907 0.0000 Watercress 2016

Sherford 50951010 Sherford River at King Bridge 1984- 32 0.0047 0.5355 2016 50951049 Sherford River at Sherford Bridge 1978- 38 0.0224 0.0009 2016

Corfe 50900736 Corfe River at Corfe Castle 1977- 39 -0.0417 0.0000 2016