Thames Water Trials Aquifer Storage Scheme

Thames Water is trialling an Aquifer Storage and Recovery (ASR) scheme in Kent which could help

ASR, more commonly used in desert regions of the Middle East and America, allows an aquifer to be used as an underground reservoir, where drinking water can be stored and then extracted again in times of water shortage. The £3.2M operational scale trial at Horton Kirby, the most advanced scheme of its type in the UK, involves a 250m deep borehole into the Lower Greensand Aquifer where water can be stored in an underground ‘bubble'.

Thames Water groundwater experts began investigating ASR over 10 years ago, and testing work carried out since 2005 had identified Lower Greensand as the most suitable aquifer. Aquifers already provide 30% of London's tap water, with the chalk aquifer at Horton Kirby being used to supply parts of Kent, but this is the first time that aquifers are being put to use for storage purposes.

Drilling began on the new borehole at Horton Kirby in September 2014, and was finished in January. By repeatedly putting water into the aquifer, allowing it to rest then recovering it by pumping it back out, the aquifer is "cleaned". This process, combined with the suitable make-up of the Lower Greensand aquifer, enables a bubble of good quality water to be stored, as only the edge of the bubble mixes with existing water in the ground. The next challenge for the Thames Water team is to be able to store a greater volume of water without it seeping away.

When in use, the ASR scheme will take ready-to-drink water from a mains water pipe and then store it in the aquifer. When the water is needed it will be taken back out and disinfected before going back into the public water supply. The water will not have to go through a complex treatment process as the water within the bubble is stored securely and does not mix with the natural, poorer quality groundwater in the Lower Greensand aquifer.

Groundwater resources manager at Thames Water, and UK Groundwater Forum member Dr Mike Jones said: "This is an exciting time for water resource development in the UK. Aquifers are a vast reserve of water storage space. In the Thames Water area there is 10 times more storage space in shallow aquifers than in the raw water storage reservoirs we've built at the surface; there is even more storage in the deeper aquifers like this one, so we need to make use of it."

"Aquifer storage isn't the magical answer to the south-east's water stress, as not all aquifers are suitable for this type of project - but it's a great start and I'm confident this work will help us understand how we can best use our natural aquifer resources in the future, especially to help combat the effects of climate change."

Ed Uden, Groundwater Team Leader at the Environment Agency, said: "This scheme is also good news for the River Darent, a chalk stream flowing through Horton Kirby and other villages in Kent. Instead of water being taken from the environment in the summer, which can cause the river flow to be reduced, the ASR scheme will allow up to 5 million litres per day to be taken from the water stored underground and put into drinking water supply, protecting the river.

Source: WWT

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Taxonomy

• Aquifer
• Water Supply
• Water Utility