Where our water comes from

Most of our water comes from rivers. Our two main sources are the Hampshire Avon and Dorset Stour, making up 88% of our supply. We also use groundwater (12%) pumped from underground sources called boreholes, particularly to source rural areas.

During the summer months we operate a stream support system on the River Allen, a tributary of the River Stour. We pump water from boreholes to help support river flows and this allows us to continue to abstract water for public supply in the area.

The surface water and groundwater systems are linked together by a network of pipes, which enable us to transfer water around the region.

River Avon

where your water comes from river avon


River Stour

river stour your water bournemouth

Making water drinkable

Water treatment starts long before the water reaches the treatment works. If raw water sources are fit and healthy, it makes our job of cleaning it a lot easier. There are many stages of treatment that water goes through before we're happy enough to send it to your tap.

river stour
Water treatment process

Raw water quality

We call water in rivers and reservoirs ‘raw’ water. Farming practices, soil runoff, industrial processes, and sewage pollutions all affect the quality of this water. If the quality is bad, more energy is needed to treat the water at our works. That’s why we do a huge amount of work as part of our Upstream Thinking programme to safe-guard our rivers and reservoirs.
Upstream thinking
water abstraction
Water treatment process


Taking water out of the environment is strictly controlled. We have to take enough to meet demand, whilst keeping enough in the environment to maintain aquatic habitats and support the wildlife that also relies on the rivers. The water is put through screens that remove large debris like branches and leaves and stop any wildlife from entering the treatment works.
water filtration
Water treatment process


The water is filtered twice. First through sand to remove any micro-organisms that are still present in the water. Then it’s filtered through Granulated Activated Carbon (GAC) that removes tiny bacteria. Did you know: GAC is full of holes that trap the bacteria inside. Just 1 gram of GAC has a surface area of 1000 square meters.

water chlorination
Water treatment process


By the time the water has been filtered, it’s very clean. We use a small amount of chlorine to completely disinfect it before it enters the pipes.

Water of the future

There are many exciting innovations happening in water treatment every year. We have some exciting projects this year, that will see a £200 million investment into our water sites, Alderney and Knapp Mill.

Projects in the pipeline

We're proud to announce a £200 million investment in upgrading our water treatment works at Alderney and Knapp Mill. This exciting project will secure and enhance the future of our drinking water supply by combining our existing, nature-based filtration system with cutting edge, sustainable treatment technology.

Projects in the pipeline image

A precious resource

With drier summers and less rainfall than the UK average, we face a unique challenge in securing a steady water supply for our customers. This precious resource requires careful management, which is why we invest in capturing, storing, and transporting water through essential infrastructure like river intakes, boreholes, pipelines, and pumps.

We are dedicated to providing a safe and continuous public water supply for everyone. We achieve this by creating a Water Resources Management Plan every five years, encompassing both South West Water and Bournemouth Water. This plan, spanning 25 years, considers population growth, environmental needs, and potential impacts of climate change.

Through responsible investments and careful management of our water sources and network, we have successfully avoided water restrictions. Our ongoing goal is to continue this success, preventing restrictions except in extreme circumstances, while always ensuring efficient water management and delivery

How you can protect our water's future

Providing 450,000 people with water is a balancing act of keeping a supply going whilst taking water from an environment that has less and less in it because of climate change. That's why it's important to be aware of your water use, and save where you can. Being water efficient isn't about not using water, but about only using the water you need.

Every Drip, Every Drop – together we can save water

It’s easy to take water for granted, but this precious resource is increasingly under threat. That’s why we’re asking everyone to use water carefully. And we promise to do our bit too.

Every Drip, Every Drop – together we can save water image