Southern Water is currently undertaking a £30 million project that involves the installation of three large hydraulic syphons, as part of an upgrade at the Bewl Reservoir.
The syphons will allow Southern Water to reduce the water level of the reservoir more quickly, if needed. For example, to carry out repairs to the dam or to reduce high water levels during periods of exceptionally high rainfall.
The equipment will be capable of moving 41m3 of water per second or the volume of 1 Routemaster bus every 3 seconds for 5 days. The pipes are 1.7m in diameter so if you are 5 foot 5 inches in height you could walk through the pipework.
Tamzyn Janes, Project Manager at Southern Water said:
“Like all reservoirs, Bewl is regularly inspected, and we constantly carry out improvements when needed. We have invested more than £30 million in this project, with the installation of three hydraulic syphons into the wall to make the reservoir easier to maintain.”
When the water in the reservoir needs to be lowered, pumps start to fill up the syphon pipework. Pumps remove air to ensure the pipes are completely full of water. Valves in the discharge chamber are then opened which starts the syphon flowing. The water discharges down to a culvert into the existing spillway and into the River Bewl.
The upgrades will future proof the reservoir against the effects of climate change. Work started in April last year. In September 2024, Southern Water drilled through a section of the wall of the dam. This has allowed them to install pipework in preparation for the installation of the syphons, which will start in late 2024. The works are expected to finish during the winter of 2025/2026.
There is a regulatory requirement to provide emergency drawdown facilities to achieve a 5m drop level within a 5-day period.
Bewl Facts
- The Bewl Reservoir can hold 31,000 million litres, held behind a 28m high, 903m long earth embankment
- Up to 26 million litres of water can be treated every day
- Bewl Reservoir has the capacity to provide up to 150 litres of water a day for nearly 200 million people
- The surface area of Bewl is the same size as 436 Wembley football pitches
- Bewl Reservoir is the largest body of water in the South East
- When full Bewl Reservoir holds the equivalent of one gallon of water for every man, woman and child on earth
