32. Point source pollution project

Aims: Involve people with their local waterbodies; Improve water quality; Work together

Water body: the whole catchment

Project description

Mapping and verifying the entry points of pollution into our rivers.

Awareness of the impact of pollution on our UK rivers is growing fast but hidden sources of pollution are undermining efforts to protect our natural environment. This project supports critical river restoration work by identifying and mapping all "potential pollution points", including hidden ones, so that we can work towards monitoring and removing them permanently. “Potential pollution points" can be anything from sewer outfall pipes, road drainage or agricultural runoff to low lying areas where pollution can accumulate before being washed into rivers by heavy rain. Knowing where these points are gives us a unique resource for tracing potential inputs after pollution events are reported, allowing us to begin the process of reporting and seeking to eliminate them. Currently information on pollution sources is incomplete and spread across multiple databases owned by a variety of institutions. The strength of this project is in the unification of those diverse sources of information, and the way we are verifying map data on the ground by conducting surveys across the catchment for these "potential pollution points". With the initial data and mapping phases now successfully completed, we are beginning the third practical validation phase of the project which is open to collaboration from anyone with an interest in local river health via use of our reporting app to identify and classify potential pollution inputs. We are eager to get volunteers across the catchment engaged in this project, so please do get in touch if you would like to get involved, whether to help out with one survey or as a dedicated volunteer. Core funding for this work has been kindly provided by our local water companies in recognition of the environmental importance of the project in reducing groundwater pollution which is a major driver of river health as well as drinking water safety and treatment cost. For more information on this project or to get involved contact This email address is being protected from spambots. You need JavaScript enabled to view it.

June 2025 Project update from Lara Clements, Rivers Officer Groundwork South.

We have been working hard to develop a comprehensive map of all potential pollution sources throughout the Colne catchment. Potential pollution sources refer to any point which may release a substance that may reduce water quality. This can include points such as outfalls, but also manholes, road run off and agricultural runoff, just to give a few examples. By producing this map we aim to provide a resource that accurately reflects the range of different potential pollution sources catchment wide.

So far, we have completed work collating and visualizing potential pollution sources from external sources. This mapping work can be viewed here:

Potential pollution sources across the Colne Catchment 

We are also in the process of conducting on the ground validation of this data through field surveys, as well as collecting any further data on potential pollution sources that was not obtainable through external sources. The results of this field surveying so far can be viewed at :

Mapped potential pollution sources 

Alongside identifying potential pollution sources, we are at the start of setting up our pollution monitoring campaign, which aims to encourage regular monitoring of the different sources we have identified through the colne catchment volunteer network. Regular monitoring will allow us to identify “areas of concern”, where we can then focus our efforts towards addressing and removing the points which are causing the greatest impact on water quality.

We are actively looking for volunteers to help out with this interesting and essential project! If you would like to get involved with this project, either through aiding in potential pollution source identification or pollution monitoring, please do get in touch with This email address is being protected from spambots. You need JavaScript enabled to view it. .

Project lead: Groundwork South

Project partners: Colne Valley Anglers Consultative, Chilterns National Landscape,ColneCan, Harrow Streams Project, Brunel University, River Chess Association, Watford Borough Council, London Borough of Hillingdon, Spelthorne Borough

Contact for more information: This email address is being protected from spambots. You need JavaScript enabled to view it.

Project start: January 2023

Funding source: Thames Water , Affinity Water