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Catchment Management

Dealing with challenges that impact on water quality at source is a more sustainable and cost effective approach than relying solely on intensive water treatment, which uses energy and other resources to remove pollutants.

Our Catchment Management Team works proactively to identify potential sources of pollution and regularly monitors rivers and groundwater in our communities. We also undertake a wide range of investigations with the Environment Agency and neighbouring water companies.

We work in partnership with local environmental groups and a number of catchment partnerships raising awareness of any issues which could affect drinking water quality. We also work with our communities to find innovative ways to reduce pollution at source, by preventing the pathways that could cause pollution to get into untreated water. Rather than relying just on engineered solutions, we believe in working with the environment through natural methods and working with others to build resilience.

Catchment management cycle

Diagram showing how pollution can enter groundwater and rivers and is then treated at the water treatment works.

River and groundwater monitoring

Understanding where pollution is coming from is a key component of our catchment work. We carry out frequent river and groundwater monitoring for a range of pollutants including pesticides and nitrates at strategic locations to help us understand the source and pathways of pollution which might affect the quality of untreated water. The data we gather helps us identify areas where we can focus our activities and work with potential polluters to find solutions that benefit everyone.

Catchment risk assessments and land use surveys

To maintain a wholesome supply of drinking water to all our customers, our Catchment Management Team carries out detailed risk assessments within each of our water catchment areas. Utilising the Environment Agency - Groundwater Source Protection Zones (SPZ) we identify surrounding land uses, such as industrial, residential and agricultural.

We capture potential risks from those land use types and assess the risks to ensure we have effective treatment in place. Where potential issues are identified, we work collaboratively with our communities to reduce the risk to untreated water quality and the environment. This supports our obligations to develop a source to tap risk assessment, known as drinking water safety plans for all of our water treatment works.

Partnership working

Working closely with our communities is at the core of our business. Our Catchment Management Team collaborate with a wide range of partners, from neighbouring water companies, the Environment Agency, Natural England, local businesses and environment groups to identify ways to improve the natural environment. We are actively looking to promote pollution prevention, by raising awareness of how domestic, industrial and agricultural activity can affect untreated water quality.

We have worked closely with the Environment Agency to identify areas from where we abstract water that are sensitive to pollution risks (Environment Agency: Drinking Water Protected Areas (DrWPA)) and through our catchment investigations, certain drinking water catchments have been designated as Safeguard Zones where we focus our activities. Our plan is to work in partnership with businesses and local communities in order to identify and implement catchment solutions.

In addition, we also support water industry research to further enhance the way in which we manage risks through better technology at the source, in the catchment and at our treatment works.

Natural England Catchment Sensitive Farming (CSF)

Mimmshall Brook Project


This project commenced in 2011 and was set up with local farmers, Affinity Water and Natural England’s Catchment Sensitive Farming initiative to address some of the issues relating to agricultural pollution which was affecting our local water abstractions.

Our investigation

The treatment works in the catchment uses water which is abstracted from the underground chalk aquifer, which is treated to meet drinking water standards and supplied to the surrounding community. Due to the karstic (fractured chalk) nature of the geology in this area, the groundwater is influenced by heavy rainfall and subsequent diffuse pollution from agriculture.

This can result in the following:

Key issues Possible impact
  • Groundwater can be influenced by heavy rainfall resulting in catchment pollution from farming products
  • Increased usage of water treatment works
  • The need to import water from other areas when pollution levels are high
  • Increased pollution means deterioration in untreated water quality
  • Intensive and costly Water treatment

Mimmshall project

Our Water Production Manager with some local farmers explaining some of the treatment needed for pesticides and other organic matter at our water treatment works.

Our involvement

Our Catchment Management Team has been working closely with local farmers on this project since 2011 to identify land management solutions in order to prevent catchment pollution, improve untreated water quality, while maintaining crop yields, help manage treatment costs and reduce the need for further treatment.

River restoration

Working in our communities to improve the habitat and flow of rivers.

River Restoration


We are committed to protecting, restoring and enhancing the different forms of living organisms on our sites.

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