Water Situation & Efficiency

After a wet autumn and winter (2019-2020) in the Thames catchment, experiencing above average rainfall, Spring saw below average rainfall, with May 2020 being the driest May in our 136 year record (Thames Water – Water Situation).

The wet autumn and winter was good for groundwater, with aquifers filling up sometimes to exceptionally high levels, and river flows also being above average. Now across the Thames region, the availability of groundwater in our aquifers is generally at around normal levels for this time of year, and while river flows are below average our reservoir storage is only just below average. The water situation has been similar in the Cotswolds and around Cirencester, with good winter flows in the Daglingworth Stream and River Churn decreasing to much lower flows in June.

Churn levels at Gloucester Street bridge in winter (left) and summer (right) 2020

As a result of decreasing river flows, and as required by our licence from the Environment Agency, Thames Water’s groundwater treatment works for public water supply at Baunton was switched off as is often the case in the summer; this year switching off in late May. This trend in river flows is consistent with groundwater levels decreasing from exceptionally high to just below normal for the time of year.  There are however some exceptions, with groundwater levels in parts of the Cotswolds being notably low for the time of year.

Although the current water resources position is reasonably healthy, our region, like much of the South East, is seriously water-stressed.  Every drop we supply to our customers comes straight from the environment and would otherwise be sustaining local wildlife and wetlands and keeping our rivers flowing. Normally, about a third of the water we supply in the Thames region is pumped from natural underground aquifers. The remainder is abstracted from rivers – however, as we move into the summer most of the river water is itself supplied from aquifers, making groundwater a truly vital source.

Over the last couple of months, we’ve seen unprecedented demand in many of our water supply areas. Due to Covid-19 very few people are commuting into central London, which has a separate water supply system, leading to a greatly increased demand across the rest of our region. With so many people at home all day, we’ve seen a massive change in the way water is used and how much is needed. This has been compounded by the unusually warm weather, and the driest May on record, leading to a huge upsurge of interest in gardening and in the usage of paddling pools and hot-tubs during lockdown.

In some areas our customers have been using water faster than we can treat it and pump it through our pipes, leading to low pressure and in some cases, interruptions to supply.  These are currently local problems, but if we have a hot, dry summer we could not only struggle to keep up with demand but also see levels dropping faster than normal in our aquifers and reservoirs.  We have never before experienced the current pattern of demand for water, and no one is sure what the next few months will look like.

Reductions in demand will have an immediate impact on the environment by reducing the amount of water we must abstract from river and groundwater sources thereby sustaining river flows and ecosystems. To raise awareness, we’ve started a four-week campaign using local radio, digital audio and social media. Through these channels, we’re explaining how water supplies have been impacted in recent months, providing water efficiency tips and asking customers to be more aware of how they use our most precious resource. We hope this, and promoting the water saving tips on our ‘How you can be water smart’ webpage, will prompt a reduction in usage and help us avoid a water shortage in coming months.

As well as the citizen monitoring records already on the Friends of the Gumstool Brook website, to keep an eye on the water situation in your local area, you might like to check out these available online data sources for rainfall at Rapsgate Rain Gauge, how Groundwater Levels at Ampney Crucis are responding to the weather, as well as the River Churn Water Levels at Cirencester.

Dr Michael A Jones (Water Resources Modelling Lead, Thames Water)

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