Chalk stream commitment

Our Chalk Stream Commitment

Chalk Stream Health

Chalk stream health is a function of flow (comprising groundwater baseflow and surface runoff), water quality, morphology and management. When all of these elements are optimised the unique ecology will flourish.

All chalk rivers are fed from natural underground aquifers and as a result they have clean and clear water. These conditions, along with their alkaline chalk geology, support a rich diversity of wildlife, including important fish populations such as brown trout, native crayfish and many other specialist species.

Our enduring commitment

The water we supply to our customers comes from the local environment and, approximately, 75% from boreholes and springs that tap into the chalk and Upper Greensand aquifers of Wiltshire and Dorset.

For decades we have sought to balance the need to supply water to our customers without compromising healthy flows in our chalk streams, and have taken steps to minimise the impact of our abstractions. In the last decade alone, we have invested more than £230 million to reduce the amount of water we take by 25 million litres per day, in order to preserve the unique ecology of these rivers.

We also ensure that customers’ sewage is conveyed and treated at our water recycling centres before being safely returned to the rivers. We have invested £50 million to improve our water recycling centres (WRCs) in order to remove increasing levels of nutrients from the sewage and reduce our impacts. We aim to remove storm overflows in the longer term and are working to understand the environmental impacts they cause and to offer improvements.

Wessex Water chronology 1995-2020

AMP2 (1995-2000)

  • Recognition of the connection between abstractions and chalk stream health.
  • Formation of Wessex Chalk Streams project with Wiltshire Wildlife Trust, EA and NE to deliver restoration projects and engagement.

AMP3 (2000-05)

  • Ecological investigations extended in the Hampshire Avon catchment to understand the effects of our operations relative to other sources and to inform future investment plans.
  • First stage phosphorus removal to 2mg/l at WRCs in Hampshire Avon and Poole Harbour catchments.

AMP4 (2005-10)

  • £50m further phosphorus removal to 1mg/l at WRC in Hampshire Avon and Poole Harbour catchments, reducing the load discharged by approximately 80%, with more than 100 tonnes per year removed in the Hampshire Avon.
  • Piloting catchment management to reduce nitrate leaching to groundwater, also benefiting the quality of baseflow to rivers.
  • Hanging Langford reedbed constructed to relieve internal flooding from groundwater and improve discharge quality [link video].
  • Further ecological and hydrology investigations which identified the need for the abstraction reduction subsequently delivered by our water supply grid.

AMP5 (2010-15)

  • Construction begins on integrated water supply grid, a £230m scheme delivering abstraction reductions and resilience. Scheme involves 200km trunk mains, 24 refurbished or new pumping stations and 12 new storage reservoirs.
  • Further phosphorus removal at additional WRC in the Hampshire Avon catchment.

AMP6 (2015-20)

  • Completion of grid, delivering 23.5Ml/d abstraction reductions (c7% of water put into supply).
  • Delivery of river restoration on the western arm of Hampshire Avon to improve riparian habitat and river flows.
  • 12% reduction in leakage across area, 60% reduction since 1995.
  • River Avon Restoration Plan wins RRC River prize.
  • Wessex Chalk Streams project celebrates 20 years, delivering more than 55 river restoration projects.
  • Abstraction incentive mechanism at Mere delivering c50% abstraction reduction.


There are numerous competing challenges to be understood when planning future infrastructure investment and enabling environmental improvements. The key challenges include:

  • balancing water abstractions with demand for water while maintaining chalk stream habitats and complying with all relevant legislation
  • improving sewage treatment to cater for increased waste from developments and providing a greater level of phosphorus removal
  • reducing storm overflow operation.

We recognise:

  • the call for higher sewage treatment standards in some sensitive locations, which could be delivered by more energy and chemically intensive treatment processes
  • the call for improvements to reduce storm overflow operation, delivered via civil engineering schemes to provide greater diameter sewers or storm storage tanks
  • the increased level of housing development across our region raising the demand for water and the volume of waste received in our sewers, against a backdrop of lowering bills to customers.

There are no simple fixes to these problems and we are keen to deliver the most sustainable solutions possible, including nature-based solutions. There is also a need for legislative changes, partnership working and increased education and awareness solutions, not all of which rest with Wessex Water.

What we are doing