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All the water that we supply to our customers comes from rivers and groundwater aquifers in our local communities. Water cannot be manufactured, so we must rely upon the natural environment which is also vulnerable to a range of pressures. A key part of our programme is to manage and mitigate these risks to ensure we provide the best quality and value of water for our customers.

What is a catchment?

A catchment can be defined as an area of land on which rain can fall and drain into a specific watercourse. This can be influenced by characteristics such as land-use type, geology and topography. Catchment characteristics can differ significantly between catchments and therefore present different pressures and challenges.

Our aim

The aim of our catchment management team is to understand:

  • The nature of each of our drinking water catchments
  • How the land is being managed
  • What are the likely risks to water quality
  • What opportunities are there to mitigate any existing issues

We complete this process in the form of Catchment Management Risk Assessments (CMRA’s). This is where we use standard methodologies such as walk-overs and aerial surveys to assess each of our drinking water catchments.

Chalk Stream Restoration Flagship Project

CaBA Flagship Chalk Stream Restoration Project

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Title River Beane Flagship Restoration Project
Location River Beane Catchment

The main aim of the CaBA chalk stream restoration strategy is to attempt to address – how to restore good ecological health to these unique rivers and the landscapes which support them.

Our initial aims for the River Beane catchment are:

  • To improve water quality, hydrological regime, river morphology to achieve good ecological status as per WFD and enhance chalk stream habitats for people and wildlife.
  • To restore water quality, and the physical habitat of the channel, banks and floodplain to support iconic chalk stream species and ecology.
  • To increase the attractiveness of the stream and public access to the river, so that people can appreciate their local chalk stream.
  • To monitor the ongoing status of the river.
Context / Background

The Catchment Based Approach (CaBA) is an inclusive, civil society-led initiative that works in partnership with Government, Local Authorities, Water Companies, businesses and more, to maximise the natural value of our environment. The project is one of twelve project under the chalk stream strategy (

Chalk streams in their natural condition are home to a profusion of life. Botanically they are the most biodiverse of all English rivers. For invertebrates, fish, birds and mammals, they offer a vast range of habitat niches. In Wessex they are a stronghold of our chalk-stream Atlantic salmon, now known to be genetically distinct. The upper ephemeral reaches, known as winterbournes, are global hotspots for a unique range of specialist plants and invertebrates.

But chalk streams are under immense pressure: they flow through one of the most urbanised, industrialised and farmed parts of the UK. Three chalk streams flow through London and there are many more in the chalk hills that surround the capital. Further afield, though many flow through more open countryside, that countryside is busily farmed, while villages or towns are sited somewhere along most chalk rivers. All these streams are impacted in one way or another by the activities of people. We depend on chalk streams for public water supply, and have leant heavily on the resources of the underground body of water that feeds these streams. And yet every litre of water we take out of the aquifers – and we take billions and billions of litres to irrigate our crops, or run our taps – is water lost to the natural environment. Lost, that is, until we put it back. Only by the time we return water to these rivers it is no longer in the state in which we found it and has bypassed long reaches of the stream. It has passed through our sewage systems, becoming rich in nutrients and other pollutants. We may treat it, we may even treat it to a very high standard in some places, but in many others we do not. Routinely, we put back into these wonderful ecosystems water which makes them eutrophic, so that oxygen is sucked away from the river life which depends on it. Even the water which we do not take out, which actually makes it to the underground aquifer or the stream, is unnaturally changed by human activities. Our heavily farmed landscape exerts a huge pressure on water quality, either because rain runs off the land and along roads, accumulating harmful chemicals and nutrients along the way, or because it seeps down into the ground carrying with it the chemical fertilisers which have been applied to the land. There is now so much nitrogen in our chalk aquifers that we do not know how long it will take – even if we stopped applying nitrogen as fertiliser – for the aquifers to become clean again. Finally, we have changed the rivers themselves, modifying them heavily over the centuries. We have used them for milling, for transport, to drive multiple agricultural and industrial revolutions. More recently, in the post-war decades, we made one of the most drastic and permanent changes of all: we dredged them. We took out the gravel river-bed – on which almost all chalk-stream life ultimately depends – and dumped it on the banks, all in an ultimately misguided attempt to drain the landscape.

Timescale Currently planned until 2035
Documents River Beane Chalk Stream Flagship Restoration Project Scoping Document

What we do

Monitoring water quality

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Another important part of understanding our catchments is monitoring water quality across our rivers and groundwater. Our team completes regular sampling of all the major rivers and tributaries in our patch. During this sampling, we take into consideration a range of variables that are important for drinking water quality. We also perform ad hoc sampling for specific investigations and respond to pollution incidents that may impact our sources.

Using the information we gather in our catchments enables us to decide, whilst working with our regulators, the Environment Agency, where we can work more intensively to stop a particular issue such as high nitrate or pesticides in water. This work is delivered under the Water Industry Natural Environment Programme (WINEP) driver. It forms the backbone of much of the work we deliver in our catchment management team.

Working with farmers

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Given that many of our drinking water catchments are dominated by agricultural land use, farmers and the agricultural sector are important stakeholders. We work with them to realise the improvements needed in our catchments.

A key focus of our work with farmers is around improving soil health. Soil covers most of the land in our catchments, apart from those that have already been built upon.

We can’t affect how much rain falls from the sky, but the next best thing we can do is influence the soil. Many farmers are working towards more regenerative farming systems. These systems put soil health at the centre of their decision-making. This means that soils will be more resilient and more able to infiltrate water. It can then slowly percolate through the soil and into our groundwater aquifers rather than running off, causing pollution and flooding issues.

Building soil health will be central to making our catchments more resilient to the weather extremes we are already seeing and they're likely to become more frequent in the coming decades.

How we're doing this

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We’re doing this by sponsoring Groundswell, a regenerative farming event near Hitchin in Hertfordshire. We’re also funding cover crops and companion crops. They help to protect farmers' soils, build soil organic carbon, and reduce runoff.

Our catchment management work is only one of many projects that are working towards improving our landscapes and catchments. It’s therefore important for us to work in partnership with others who also play a part in the health of our water courses. We sit on all the catchment partnerships in our patch and contribute where needed. We also work in partnership with other water companies where our catchment boundaries overlap. For example, we're joint funding the EnTrade cover crop scheme with Cambridge Water. We're also participating in the Thames Catchment Management Steering Group (TCMSG) with Thames Water and South-east Water.

Catchment management for a water company has primarily focused on improving water quality. However, in recent years, our work has become more holistic. We aim to maximise the wider benefits that can be obtained from working at a landscape scale in our catchments. Interventions that are good for water quality and water resources can also benefit biodiversity, mitigate climate change, and improve air quality, as well as make the environment in which our customers live a better place.

We’re currently working on PR24 for our AMP8 business plan. We aim to invest in catchment projects that not only benefit the water environment but, where possible, maximise other ecosystem services.

Our projects

Improving the health of chalk streams

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Title Landscape Enterprise Networks East
Location Upper Lee
Objective/aims To improve the health of our chalk stream catchments though partnering with other organisations who want to fund environmental improvements in the landscape. The other funders include water companies, food manufacturers and county councils, with other funders being sought.
Context / Background We're working with farmers in our catchments to encourage and incentivise land management practices that protect water and the wider environment. Partnering with other buyers of ecosystem services through the LENs East of England project, we can share the costs of these measures and increase the impact on a landscape scale. Many measures have multiple benefits; for example we can pay for the water quality outcomes, others can pay for carbon, biodiversity and flood risk outcomes, lowering the cost to each buyer and making the money spent on environmental gain go further. We were particularly interested in the project’s focus on regenerative farming and carbon sequestration in landscapes, an approach that can benefit both our local catchments and the climate.
Description LENs works by establishing and managing a regional trading system of collaborative value chains, each driving specific landscape outcomes for different groupings of businesses. East Anglia’s economy has long been rooted in its productive landscapes, characterised by rich soils, aquifers and accessible topography. In recent decades, a growing population and new knowledge and tech industries have joined the agricultural sector in putting pressure on the land and its natural resources. This made the area ripe for public and private sector collaboration to tackle commercial and sustainability challenges, including drinking water quality, flood protection, security of wheat supply and reduction of greenhouse gas emissions. East Anglia’s predominantly arable farmland supplies milling and feed wheat for facilities operated by Cereal Partners UK and Nestlé Purina. Anglian Water delivers both water supply and wastewater services to the region, while Essex and Suffolk Water and Affinity Water also provide water supply. CISL and 3Keel worked with these initial partners to develop and design the project over two years. Launched in Northamptonshire in 2019, the project area has spread across Cambridgeshire, Bedfordshire, Hertfordshire, Norfolk, Suffolk and Essex . The first trading process was completed in summer 2021. Affinity Water participated in the first year's development and have committed to fund measures in the second year's trade. The project area has increased in coverage from 4,335 hectares to 25,000 hectares. Affinity Water are funding measures this year such as year long cover crops, reducing surface run-off from farm tracks and the use of nitrification inhibitors to limit nitrate leaching.
Timescale Annual trades occur, the next trade is due in spring 2023 for implementation across 2023/24
Photos Flowers

Promoting improved soil health

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Title Farming 4 clean water scheme
Location Upper Colne, Mimmshall Brook and Essendon catchments
Objective/aims To work in partnership with local farmers to promote on-farm practices with the aim of promoting improved soil health and more sustainable pesticide use which benefits food production and the environment by reducing losses of certain pesticides entering water courses and posing a risk to drinking water supplies.
Context / Background "Affinity Water abstracts groundwater from the Upper Colne, Mimmshall Brook and Essendon catchments and therefore these groundwater catchments are classed as Drinking Water Protected Areas (DrWPAs) and must meet strict water quality standards set out by the Drinking Water Directive. When certain substances such as pesticides are detected in raw untreated water, the Environment Agency will define the DrWPA as ""at risk"" therefore Affinity Water are regulated through the Water Industry National Environment Programme to implement catchment based measures to identify the source and work with relevant users to mitigate the risk to drinking water supplies. As well as having robust treatment processes at nearby works, catchment management is a sustainable way of improving water quality at the source and ensuring resilience of water supplies. Our investigations have shown agricultural use of metaldehyde slug pellets and certain herbicides used on oilseed rape to be the main contribution to high concentrations detected in water courses and groundwater across these catchment areas. The unique karst geology in the area which is characterised by the formation of swallow holes (stream sinks) allows surface water to rapidly infiltrate into the aquifer which elevates the likeliness of detections of pesticides used in the catchments. The challenge the geology poses has required some innovative solutions from an engaged and willing farming community to help protect drinking water quality."
Description "Affinity Water’s catchment management team first started working in partnership with the farming community in the Mimmshall Brook back in 2014 as part of the Metaldehyde Stewardship Group pilot project to address metaldehyde concentrations being detected in raw water. Metaldehyde is not easily removed using traditional treatment processes and therefore farmers were asked to voluntarily switch to environmentally friendly ferric phosphate pellets in high risk fields. This pilot was a success in reducing the seasonal peaks in metaldehyde concentrations, however due to the presence of swallow holes in the catchment a broader approach was required to remove the use of metaldehyde pellets. In 2017, the Farming 4 Clean Water scheme was launched and expanded to the Upper Colne and Essendon catchments where metaldehyde was also being detected. Farmers agreed to not use metaldehyde pellets on any arable fields within this wider scheme area and instead use ferric phosphate pellets and cultural controls such as beetle banks to provide habitat for predators of slugs. Monthly water quality bonus payments were available providing that water remaining below the drinking water standard (0.1 micrograms/litre) in raw groundwater and at key surface water sample locations. This scheme was a success and helped significantly reduce metaldehyde concentrations in watercourses and groundwater across these catchments right up to March 2022 when the ban on the outdoor use of metaldehyde came into force. This is a great example of collaborative working to safeguard drinking water supplies and provided the foundation for the more aspirational and innovative scheme in place today. The Farming 4 Clean Water scheme now focuses on improving soil health and implementing in-field approaches which can not only reduce losses of pesticides but can also help fix nitrogen in the soil to improve food production and prevent nitrate being leached to groundwater, create habitats to improve biodiversity and increase organic matter and soil carbon storage potential. In 2021, Affinity Water teamed up with EnTrade to create a tailored, online environmental trading platform which allows farmers to select their fields and bid for funding to implement measures to protect water and the environment. In 2022, a number of options could be bid for including: • Companion cropping of oilseed rape with another crop such as berseem clover, fenugreek or buckwheat. These companion crops add diversity and extra vegetative cover which can prevent runoff of herbicides which we detect in raw water. Some companion crops can also help with pest control, fix nutrients which can be used by the oilseed rape crop and build organic matter in the soil after the companion crop breaks down. • Alternative break crops to oilseed rape in areas close to water courses and swallow holes where the chances of herbicides being lost is high. A number of these alternative crops are grown in spring instead of winter and require fewer herbicides at a lower risk time for rainfall • When farmers grow spring crops, an over winter cover crop can prevent bare soil over the winter reducing sediment losses during rainfall events and fix nutrients in the soil. These cover crops can be used as green manure for the next crop and the above and below ground biomass will help build organic matter in the soil. Uptake in 2022 has been very positive and over 700 hectares of arable land across these catchments will be funded to implement these measures. We have been able to target our interventions more effectively by co-funding a collaborative PhD research project with the University of Leeds, British Geological Survey and Environment Agency to investigate the karst geology across these catchments which included tracer testing to better understand where some of the larger swallow holes feed into the groundwater and how this impacts our sources. Small concentrations of harmless bacteriophage were injected into swallow holes across these catchments and extensive water samples were collected at our sources and springs across these catchments and into the Lea Valley. Significant connections between surface water and groundwater have been quantified which allow the Catchment Management and Biodiversity team to work with landowners to implement more radical land use changes close to these features such as taking land out of production and support for long term stewardship options. The Farming 4 Clean Water scheme has demonstrated the value of working in partnership with the local farming community to improve soils and create more resilient catchments. Participants of this scheme have shown their willingness to be stewards of the local environment and protect water supplies to ensure we can supply high quality drinking water which our customers can trust. "
Timescale Ongoing
Photos Field   FieldField with group of people

Investigating nitrate in groundwater

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Title Nitrate Groundwater Investigation and Trends
Location Affinity Water Ground Water Abstractions Source Protection Zones 1-3 (SPZ)

To investigate and determine the source(s) and pathway(s) for nitrates that affect the quality of water abstracted at pumping stations.

To inform future investment plans for Affinity Water, both in terms of catchment management and treatment in AMP8 and beyond.

Context / Background Nitrate is found naturally in the environment. The Drinking Water Directive has set a standard of 50 milligrams per litre (mg/l) for drinking water. However however excess nitrate from anthropogenic sources can lead to increased concentrations above natural concentrations. This can include diffuse arable sources such as fertilisers in agriculture, or more point sources such as sewage misconnections. As a consequence, for some groundwater sources there is a risk of exceeding the Drinking Water Directive standard of 50mg/NO3."

Identifying sources for investigation

Affinity Water undertakes routine catchment risk assessments for all its sources, this includes reviewing 'raw' water quality data which is sampled before any treatment. These regular reviews identify sources that may require a thorough investigation due to poor water quality or trends indicating deteriorating water quality. In the case of nitrate if the concentrations follow a seasonal trend this is likely to be a diffuse source and/or influenced by groundwater levels. However, if the nitrate concentrations follow a diurnal pattern or have sporadic spikes, then it is likely related to a point source.

Nitrate investigation methods

A desk study and field is carried out on investigated sources. This can range from identifying all land uses that may contribute towards nitrate in groundwater, as well as recent developments that may impact the source. Additionally any pollution incidents within the catchment are investigated, conceptual modelling of the abstractions groundwater catchment, where appropriate sampling rivers and drilling observation boreholes to monitor nitrate levels, engagement with local landowners and farmer surveys, remote sensing wet weather walkovers, historic cropping, waste water infrastructure mapping. These methods are all carried out to determine the source of potential pollutants sand the pathways to abstraction.

Abstraction nitrate modelling

In the most recent nitrate investigations, hydrogeological modelling by Stantec was used to determine the key inputs of nitrate, spatially map nitrate inputs, predict long term averages and ranges trends. Some examples of this are shown below. In addition, Stantec included modelled scenarios of potential future catchment management schemes and how reductions of nitrate concentrations could be made to reduce long term trends.

Outcomes of investigations

Overall the investigations allow Affinity Water to make an informed decision for future management of its sources, taking into account appraisal of catchment management schemes to reduce nitrate, cost of installing or upgrading treatment, and long term sustainability of the aquifer.

Timescale April 2020 - March 2022

Remote-Sensing of Land-Use

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Title Remote-Sensing of Land-Use/Cover Change and Pollution Sources
Location All Affinity Water Groundwater Abstraction's Source Protection Zone 1 (SPZ1)

Has covered:

  • Evaluating the potential for remote sensing to identify changes in land use and other activities which may present a pollution risk to water supplies.
  • Establishing thresholds and criteria on which site investigations or additional data capture can be based.
  • Undertaken a risk review of all SPZ1s Will continue with:
  • Presenting data in a user-friendly dashboard for ongoing operational management of pollution around extraction sites.
  • Integrating the completed system into the current risk assessment methodology
Context / Background Affinity Water undertakes routine catchment risk assessments of its sources which include a walkover of the catchment as part of the Drinking Water Safety Plan (DWSP). Recent pollution incidents that have caused groundwater pollution identified the need to explore the additional use of satellite imagery as part of the survey. Development of an automated system is required to identify abnormal areas of change from the seasonal norm across multiple satellite images of the same area, and needs to notify Catchment Officers of areas for investigation.

In summary, the key objective is to provide an early warning to the Catchment Management team that would trigger desktop and site investigations, enabling timely interventions which could prevent or mitigate contamination to the aquifer.

In response to this requirement, it has been demonstrated, through the initial scoping and proof of concept development phases the efficacy of remote sensing for identifying a range of sources of pollution through a series of pilot workflows and prototype analytics dashboard. These methods were subsequently applied across all SPZ1 sites, with additional detailed manual interpretation applied to a subset of priority sites. This provided AWL with an up-to-date risk review from satellite data across all SPZ1 sites.

The piloted analysis workflows need to be implemented within an operational software environment to provide ongoing, periodic monitoring across SPZ1 and SPZ2 sites. This data can be integrated into a user dashboard to aid in review of anomalous data and prioritise further inspection, including site visits. The proposed system will provide an integrated system for management of pollution sources within SPZs that allows a significant volume of imagery data to be automatically and frequently captured and analysed with up to a monthly frequency. A built-in prioritisation based on trigger thresholds will allow for consistent methods for identification of potential incidents and clear processes for triaging and managing response activities.

Timescale April 2021 - April 2023
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