Low flows for the River Thames at Reading is likely to continue

Coutersy of Callum Cromwell, Callum’s Night Photography

Reading Hydro volunteer Wilson Chan is a PhD student at Reading University, carrying out research on the impacts of climate change on UK water resources.  He’s applied his data modelling expertise to predict likely flow in the River Thames over the next few months. In a future blog he’ll update the data and also discuss the likely impact of climate change on the Thames flow. It’s great to have Wilson’s data modelling expertise to help us understand river flow better (even though the outlook is somewhat gloomy for the next few months….).

July 2022 has been confirmed the driest July on record for southern England.  The same month also saw a record-breaking heatwave with temperatures reaching 40°C for the first time. Precursors to the latest drought were a drier than average winter and spring 2022, and the driest winter-spring sequence since the 1970s. The flow of the River Thames at Reading has been declining since spring 2022 and high evaporation from the exceptionally hot and dry summer has exacerbated this decline. This low flow means that Reading Hydro hasn’t been able to generate electricity since June. So what is the outlook for the coming months?

To look at this, I followed the UKCEH Hydrological Outlook “Ensemble Streamflow Prediction” (ESP) technique based on historical climate to look at the likely river flows over the coming year. Details of the model and technique are in this paper, and the results are summarised in the graphs below.

The black line at the left of the upper graph is the actual flow of the Thames at Reading up to August 2022.  Each of the 56 grey lines that continue from August suggest the possible flow for the coming year, modelled by assuming that the rainfall and temperature will be identical to one of the past 56 years. The variation in weather from year to year leads to a large variation in predicted river flow, as anyone who has lived in Reading for a long time would expect. I have highlighted what would happen if we have a repeat of weather from particularly dry years (i.e. 1976, 2003 and 2011).  

It’s useful to see the wide range of plausible flow rates, but how do we know what flow is likely on a given future day?  The approach I used is to calculate the percentage of simulations falling in defined ‘bands’ of flow rate, which gives the probability that, based on past weather, the flow on a particular day next year will lie within this band, as shown in the lower graph.  Here, I’ve chosen thresholds relevant to Reading Hydro: a) 5.24 m/s, the hands-off flow below which we are never allowed to generate, b) 11.44 m/s, the minimum flow required for full generation and c) 37.9 m/s, the average flow of Thames at Reading.

The prediction isn’t very encouraging. It suggests that, without exceptionally high rainfall soon, there is a high likelihood that river flow will be below the level needed for the Reading Hydro turbines to re-start operation, until at least October 2022.

Why we are not generating

You will have noticed if you regularly walk past our turbines that they haven’t been turning for quite some time If you look at the power generation page on our website you will see that Reading Hydro hasn’t generated any electricity since 1st July.  You can also see from the river conditions data on our website that the Environment Agency river flow sensor at Reading Bridge currently reads just over 3 cubic metres per second (m3/s). This is less than 10% of the average river flow.  At this very low flow rate, the Environment Agency cannot allow Reading Hydro to use water to generate electricity, because they must prioritise providing water to the fish passes and the weir gates.

We knew that in some summers there would be periods of no electricity generation because of low river flow rates. This was taken into account in the estimate of average annual generation, and resulting income, in our business plan.  But the shortage of water this year is extreme. 2022 has, to date, been the driest year in England since 1976: the Thames region has experienced the driest July since 1911, and we are now officially in a drought.

We’ll keep you posted as conditions change.


The broken bearing

You may have noticed if you have walked past our turbines or looked at the live data feed on our website that we have only been running one of the two turbines for half of May.  This is because we have had a bearing failure on Turbine 2 (Sophie), the one furthest away from the View Island bank.

We have an automatic condition monitoring system fitted to the turbines and, early on 13th May, we received a Red alert alarm for the bearing that supports the top end of the Archimedes Screw.  Spaans Babcock, who made and installed the turbines, came straight to site, and told us that we needed to shut that turbine down.  The bearings should last 10-15 years so the failure was not expected.  Spaans had to order some spare parts, and then arranged to come and replace the bearing, under warranty, starting on 30th May.  The turbine started running again on 1st June. 

In order to replace the bearing we had to remove the water from the outlet channel of Turbine 2, which we had not done before.  This was achieved by lowering wooden planks – stoplogs – into the grooves at the end of the channel and sealing the wooden wall this made with a tarpaulin. Once this was done we were able to pump the water out of the channel.  After Spaans had completed their work we carefully removed the stoplogs, allowing water back into the channel.

Although both turbines are now running again the water level in the River Thames is now low which means that we are not always able to generate full power.  The Environment Agency requires Reading Hydro to shut down when the river levels are below an agreed ‘set level’ to make sure there is enough water for navigation.  When the upstream level gets close to the set level, power generation is reduced.

Fitting stoplogs across the outlet channel for Turbine 2

Historic aerial photos of the Hydro site

This aerial photo was taken in August 1928 and shows Caversham Weir and View Island towards the bottom of the image.

A large house can be seen on View Island along with gardens and another smaller property.

On the Reading side of the Thames, what is now Thames Lido is visible in Kings Meadow. This was built in 1902 as the Ladies Swimming Bath; the Men’s Swimming Bath (now demolished) is slightly closer to the town centre and when built in 1879 was the largest pool in the South at 79m x 24m. Reading Bridge was a relatively recent addition, having been built in 1923.

Given the shadow lengths, this October 1955 photo would have been taken in the late afternoon, facing the opposite direction to the earlier photo. Some aspects are very similar – there is still an extensive collection of railway sidings near Reading Station and the two open air pools are still visible. However, the Men’s Pool was disused by this point and the site was sold the following year for development as offices and workshops.

On View Island both structures have been demolished and there is a new footbridge between Hills Meadow and View Island, although this has now gone.

Data Pages at Reading Hydro

Great news! Reading Hydro’s turbines have both been running full-time since 22nd November (apart from short periods of scheduled maintenance on Saturday mornings).

You can see this for yourself on the Performance data pages of our website. The main page gives a snapshot of all the data – the current power generation of each turbine/generator, the water levels, and the turbine house environmental conditions. There are then links to more detailed pages on Power generation, Water levels, and the Environmental conditions. These have graphs that show historical data for some values. You can look at the performance over different time periods, and for one or both turbines.

It’s thanks to Reading Hydro’s fantastic Digital team that we have these pages. Live data is needed by our operations and maintenance O&M team and the Environment Agency to keep a check on how the hydro plant is working. But equally important, we want it to be available for anyone to see. 

The team collects raw data from the turbine house control system, and processes it into the website display format. There have been teething problems including checking sensor calibrations, so we aren’t displaying water flow because we’re not yet satisfied with these measurements.

The Digital team is constantly improving the data display to make it easier to read, and more accessible for people with visual impairment. Our website usage stats show that (not surprisingly!) the data pages are the most popular ones on our website, and many people view them from mobile phones. So the processing has been changed to make the data display update more quickly, and look better on mobile browsers. 

For anyone interested in the technology behind this, it is documented on our github page.

Thanks to all the Reading Hydro Digital team – Arabela, Mark, Stuart, Bapu and in particular Lynda for the website work.

Installation of a UPS in the Turbine House

UPS in the Turbine House

Why do we need an Uninterruptible Power Supply (UPS) in the turbine house? Don’t we have enough electricity there?

The reason is to make sure that our monitoring systems keep working, even if something happens to shut down the turbines. In fact, that’s when the monitoring is most important, so that we can see what happened, and access the controls to rectify the problem if it can be resolved remotely.

We now have this critical equipment on the UPS. We hope it’s never needed, but we are ready if it is.

Why we may not be generating

We finally had all permissions and procedures in place to start generating on September 1st. But once again the weather was not on our side. It stayed stubbornly warm and dry for over three weeks, and the river flow was too low to start. At last it rained, and the Environment Agency gave us the go-ahead to generate on September 29th. Our new O&M team raced into action, and Reading Hydro came to life. 

We are currently having some teething issues with the system that we are working hard to resolve, and hope to be fully operational in a few weeks.  Whilst we sort out the issues you may see the turbines running intermittently.

Reading Hydro Official Opening Ceremony

Reading Hydro cbs is very pleased and proud to announce that our two reverse archimedes screw turbines by Caversham Weir are now officially operational and ready to generate clean, sustainable energy to the benefit of the reading community.

Watch our Opening Ceremony Video here

With speeches from Sophie Paul (Chair), Dr Tony Cowling (Founder), Andy Tunstall (Comms Director) & Matt Rodda MP (Reading East), our ceremony was attended by 35 people who had been identified as committing above and beyond to making our project a success. The ceremony saw our ceremonial plaque unveiled and a letter from Alok Sharma MP (Reading West & COP26 President) read out, underlining his support for renewable energy projects and reaffirming the UK’s commitment to a successful COP26 summit. The switching on of the Reading Hydro turbines for generation was accompanied by music from local band Turny Down, some of which you can catch in our video above.

The Board of Directors thanks all those who came to support our opening, as well as the wonderful coverage provided by both the BBC and ITV who did live broadcasts from our site by Caversham Weir. The Board also wishes to thank our community of members, shareholders and volunteers who are all vital to the success of this project. Plans regarding guided tours of the turbines will be shared with the community in the near future, and we look forward to welcoming you to site to see the culmination of your investment and hard work.

With Many Thanks,

The Directors,
Reading Hydro CBS Ltd

Turbine House Mural Unveiled

Reading Hydro Mural
Our mural was commissioned following an open competition, with our winner chosen from 11 fantastic entries

Another Step forward

READING, UK: Reading Hydro CBS formally unveils our Turbine House Mural as the latest addition of public artwork to the burgeoning art scene in the town. With the screws now installed and commissioning underway, unveiling our new mural denotes two important points for our project; the return of the weir footpath for public use and another step towards electricity generation on the Thames in Reading. As such, with users returning to the weir, it’s thrilling that there is a new feature for the public to enjoy on their way past our site.

Designed by artist Guglielmo Miccolupi, of the solarpunk collective Commado Jugendstil, ‘Community Energym’ represents the Reading Hydro community and the sustainable power the project will generate. Chosen from a impressive selection of entries, the judges noted the artwork’s inspiring design and exceptional presentation. The application process to the walls took place over May 2021, with the assistance of over 20 volunteers. The end result is a high-quality and visually stunning artwork, enjoyable and appreciable to the Reading community from Hills Meadow and the Caversham Weir.

The Mural at our site by Caversham Weir


The piece makes full use of the brief for a fun, engaging artwork about community energy and sustainability. Featuring Archimedes, Mother Thames and droplets from the river, the mural shows how our turbines will generate community power. The droplet’s movements in Archimedes’ gym, generating electric bolts to power our community light, is “…a fun and powerful metaphor to show the interaction between the river and the turbines…”. Mother Thames, sitting beneath the clear message about our project; “This Energy is By the people, for the People”, signifies our wide community of shareholders and volunteers. Without their combined effort, our project would not be the success it has become.

The Reading Hydro Board therefore passes on its sincere thanks to Guglielmo & Laura for their superb efforts and the wonderful gift they have given Reading. We hope the unveiled mural helps bring the community together regarding sustainability and hydropower for many years to come. Thank you!

You can find out more about the mural on its dedicated webpage.

Gallery of mural images taken on site


Reading Hydro are pleased to announce that the submitted design of Guglielmo Miccolupi, of Commando Jugendstil, has been selected as the winner of our competition to design a new community mural on our Turbine House by the Caversham Weir, in Reading, UK. Commando Jugendstil will be familiar to many in Reading as the collective leading the Transition Network workshops exploring the sustainable future of our local community out to 2045. Reading Hydro are thrilled to be working with the collective to add to the growing public art scene in the town.

The entry, entitled ‘Community Energym’, conceives of the water of the River Thames going to the gym and using the machines to exercise and generate energy, with help from both Archimedes and Mother Thames. The design appealed to our judging panel for its universal attraction and extremely high quality execution. The full design will be publicly unveiled in the coming weeks both jointly at our site and on our website.

“We wanted to create a visual that could be both playful and engaging, so we played with the concept of water generating energy, and we came up with the idea of drops of water going to the gym, doing sports and using the machines to generate energy. We thought this could be a fun and powerful metaphor to show the interaction between the river and the turbines”.

Commando Jugendstil

Our warmest congratulations to Guglielmo and the collective for winning, and our sincerest thanks to the 10 other artists who provided such strong and beautiful submissions. Reading Hydro firmly believes that the high standard of submissions received reflects a strong and growing artistic community within the town, and that our mural will contribute to the bright future for cultural works and opportunities in Reading.

The Directors
Reading Hydro CBS