Water Situation & Efficiency

After a wet autumn and winter in the Thames catchment, experiencing above average rainfall, spring has seen 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)

A wet winter and full water courses

This winter has been much wetter than normal; frequent and sometimes heavy rain has filled local streams and the River Churn to unusually high levels for an extended period. The photo shows the water flowing past Cirencester’s outdoor swimming pool on 29th October. The pipe crossing the stream is normally well above the water level, and although no longer covered now, the gap between pipe and water remains unusually small. The water meadows along the course of the Churn have been partially flooded for three months now.

Of course, some winters are wetter than others and that has always been the case. 2019/2020 has not been exceptional in the long-term record, and it’s been good to see water levels consistently high for an extended period when we’ve so often witnessed the Daglingworth Stream completely dry between Stratton and Cirencester in summertime. Will this happen in 2020? We’ll have to wait and see.

Our local watercourses are always fascinating, ever changing, and with some interesting wildlife. If you haven’t done so recently, pick a dry, sunny day and treat yourself to a stroll along the Churn and its associated streams. OpenStreetMap marks most of the smaller paths and shows the water courses clearly, all an easy walk from the Market Place.

Chris Jefferies

A sluice in time

The humble sluice gate doesn’t get a lot of attention – unless things go badly wrong. All managed water courses have sluice gates to control the flow, and the Gumstool Brook and its associated channels are no exception.

A kingfisher on the bank of Riverside Walk 16th November 2019

There is good news this winter. The sluice feeding Barton Mill Pound from the River Churn is open and water is flowing well along the Riverside Walk; excessive levels are prevented by the recently constructed overflow into the water meadow north of Riverside Walk. The Mill Pound and the channel past the outdoor swimming pool are now full, and consistent enough in level that they’re frequented by water voles and a kingfisher. What a delight it is to spot either of these wonderful creatures. Look out for moving, rustling leaves on the bank at dusk (water vole), or a flash of blue during the day (kingfisher).

There’s an important sluice gate from the stream past the swimming pool into the Gumstool Brook between the horse paddock and the back gardens of The Mead, and this remains closed. So despite wet weather and high water levels, the Gumstool Brook is lower than it would be if the sluice was open, and properties in and around the brook are protected from flooding. (Note: the Friends of the Gumstool Brook have no control over these sluice gates; they are managed by various authorities.)

Chris Jefferies