Security of supply

A consistent finding of surveys is that customers give high priority to secure, uninterrupted water supply. This underpins our long term investment and day to day management of water resources.

The index that measures security of supply to our customers again remained at 100% for 2009-10. While we currently have sufficient water resources to meet demand, future challenges we face include:

• the possible impacts of climate change
• dealing with possible source failures, such as recently experienced by Severn Trent Water after flooding of their water treatment works in Gloucestershire in 2007
• deteriorating raw water quality
• meeting additional demand from a growing population.

All these present challenges to the resilience of our water supply system in providing communities with water and the related security of supply.

During 2009-10 we completed a number of projects to improve the security of water supply in Wiltshire, Dorset and Somerset including improving trunk main transfers to reduce the number of customers dependent on a single source.

In our water resources management and business plans, we also proposed the development of an integrated water grid to improve our resilience to future challenges.

What is the proposed water supply grid?

We already have a network of strategic supply mains which mean that we can move water across our region for our normal day to day operations.

Modelling has identified where network improvements or additional connections were required to cater for events beyond the capabilities of our existing system, eg, flooding, gross pollution and fire.

This led to an outline design for the development of a more integrated grid which would involve additional new pipelines, particularly:

• a new pipeline to move water from Ringwood to the Salisbury area
• new and upgraded pumping stations to move the water around
• additional service reservoirs to store the water.

It is important we meet new demands and ensure communities are served by more than one source of water. We are developing a 112km regional, water supply grid that will take eight years to complete. It will involve connecting a major part of the water supply network from the north of Bournemouth, through Salisbury towards Bath.