Catchment management

Catchment approach

At Cambridge Water, we’re committed to providing a consistent supply of high-quality water to all of our customers now and for future generations. This means taking care of the environment to ensure that the water we provide is safe to drink and of the highest quality.

Our drinking water is taken from the Chalk aquifer which lies to the south and east of Cambridge. One advantage to using groundwater for our drinking water supplies is that the layers of rock naturally filters the water, so the raw water often  requires very little treatment. However, many of these sources have been deteriorating in quality over a number of years due to rising nitrate concentrations in the aquifer, which cannot be filtered out by the Chalk.

A catchment is an area where water is collected by the natural landscape. In a catchment, rainfall not used by plants either infiltrates into the groundwater or as surface runoff; eventually flows into surface water systems such as streams rivers, lakes and the ocean

Agriculture, forestry, industry, waste management and water abstraction all have an impact on the catchment and on the quality of the water within it.

What’s the quality of raw water like in the Cambridge region?

All of the Cambridge Water sources have seen an increase in nitrate concentrations and the trend is continuing to increase. The nitrate is believed to have come from the land uses in the catchment, mostly agriculture. A lot of the nitrate concentrations that we are seeing at the moment are a historical issue due to the time delay of substances working through the various layers of rock.

We are currently working with farmers in our catchments to try and reduce future nitrate concentrations and to hopefully reduce the risk of any other water quality issues such as pesticides. 


Metaldehyde is the active ingredient in the majority of slug pellets used by farmers and gardeners.

Metaldehyde can be washed into watercourses during periods of high rainfall. The drinking water standard for pesticides is a maximum of 0.1 micrograms per litre (0.1µg/l). While this is not a health based standard and it is not harmful at these concentrations, it is a legal requirement that must be met. 

As there is no cost-effective treatment to remove metaldehyde at present, we’re aiming towards management of the catchment to tackle the problem at source and reduce the risk of non-compliance with the drinking water standards.


Nitrogen is an essential nutrient for plant growth and is regularly applied to agricultural land as nitrate in fertilisers. Agricultural fertilisers can leach into groundwater and run-off into surface water creating water quality issues.

Over the last 30 years levels of nitrates in the raw water supply have been increasing to a point where some levels exceed the drinking water standard for nitrates. Historically our approach has been to ‘blend’ water from different sources. This involves mixing water with higher concentrations of nitrate with water which has lower concentrations to ensure all water meets the required standards. Where this is not possible we have to treat the water at special nitrate treatment plants.

What are our long term goals for managing the quality of raw water?

Treating water is not cost effective or environmentally sustainable.

In addition to chemicals which we may have to use, our treatment works require maintenance and have operating costs which increase our carbon footprint.

A sensible approach is to ensure we do all we can to take care of the environment and improve the quality of the raw water – this is known as catchment management.

We aim to rely less on ‘end of pipe’ treatment solutions and to improve the overall quality of water in the whole catchment through this approach.

 How are we going to achieve this?

Collaborate – working in partnership with landowners, farmers and regulators, such as the Environment Agency, Natural England, Drinking Water Inspectorate, Staffordshire Wildlife Trust, River Trusts and other water companies to develop framework agreements and share information and resources

SPRING 2 - SPRING 2 is an Environmental Protection Scheme set up by South Staffs Water to help farmers explore catchment friendly land management. Under the scheme, farmers are able to apply for a grant of up to £10,000 per farm – towards the costs of voluntary on-farm infrastructural improvements and land management options designed to protect the environment and improve water quality. Find out more about SPRING.

Research - Carry out research on our catchments to better understand how they operate

Take action - Actively participate in initiatives which encourage catchment friendly use of agrochemicals and enhance biodiversity

Educate - Inform people about the impact catchment management can have on improving the quality of raw water through awareness raising events and visits to our treatment works and reservoirs

What are our long-term goals for managing the quality of raw water?

Up until recently we have relied on ‘blending’ raw water that has exceeded the legal limit for nitrate but unfortunately we are now reaching a point where our ‘low-nitrogen’ water is too high to blend the higher concentration water to an acceptable level. Therefore, we have had to invest in ‘end of pipe’ treatments at some of our sources to help ensure we meet the legal limit for nitrate concentrations.

Using treatment to remove the problem is the not the most sustainable nor cost effective way of ensuring the long term protection of our drinking water, as treatment works have additional operating costs, require maintenance and increase our carbon footprint. Our approach is to combine treatment in the short to medium term with a wider catchment approach aimed at improved land management for the long term. Catchment management means that we will work collaboratively with landowners, partnerships and local interest groups by raising awareness of the problem of nitrates and working to lower the input of nitrogen at the source.

If you are interested in finding out more about catchment management at Cambridge Water, please email the catchment management team