Catchment management

What is catchment management?

Catchment management is the process of looking after the raw water quality of our rivers and groundwater sources by reducing contamination. Contamination of watercourses presents an ongoing problem for all water companies due to the nature of diffuse pollution.

What is diffuse pollution?

Diffuse pollution is the release of potential pollutants that in small amounts may have no effect on the water environment, but at scale can have a significant effect. Problems occur in both rural and urban environments. Rural examples include: run off from farmland, forestry activities and green spaces. Urban examples include: run off from roads, houses and commercial/industrial areas.

Our approach

Our catchment is approximately 11,000 sq. km in area. It includes the River Thames and the River Lee and their tributaries, and can be divided into a number of sub-catchments.

The EU Water Framework Directive (WFD) encourages catchment-based solutions to safeguard water, rather than adding additional expensive treatment at water treatment works. To follow this directive, water companies set up catchment management initiatives with local stakeholders to identify pollution pathways and work with landowners to address diffuse pollution.

To improve our understanding of the catchment, we undertake the following activities:

  • Collect river water samples from over 100 sampling points in Thames Water’s catchment to identify ‘hot spot’ areas where pesticide concentrations are high
  • Work with the Environment Agency to identify Safeguard Zones
  • Work with the crop protection industry, land owners, farmers, and other stakeholders
  • Investigate the likelihood of agricultural pollution reaching the rivers following rainfall by using information such as soil type, gradient and land use.

These activities provide us with a greater knowledge of the catchment, which allow us to identify and mitigate risks, engage with stakeholders, and protect our water sources. Two of our biggest focuses are on detecting and reducing Nitrates and Metaldehydes in our catchment areas.

Who we work with

Catchment Management cannot succeed without the support of stakeholder organisations. These groups help us to make contact with farmers and coordinate projects. Here are a few of the organisations we work with:

Contact Us

If you’d like more information on catchment management, please email us at

If you see evidence of pollution, or believe an incident may be imminent, please call us on 0800 316 9800. Lines are open 24 hours a day.