Perhaps you’ve never considered where London gets some of its water. The Knight Reservoir is a crucial part of that story. It’s a large pumped storage reservoir in Surrey.
The Knight Reservoir was inaugurated in 1907. It holds a massive 2,180 million liters of raw water. This water is drawn from the River Thames. Before it reaches your tap, it undergoes treatment. Then it supplies London and north Surrey.
Let’s step back to the late 1890s. The Southwark and Vauxhall Waterworks Company needed more water storage. They sought permission to build two reservoirs near their Hampton works. This was made possible by the Southwark and Vauxhall Water Act of 1898. The act allowed them to build reservoirs, an intake from the Thames, a pump house, and filter beds. Construction began in 1898 on the site of Apps Court. This was an old mansion.
However, the project wasn’t finished when the Metropolitan Water Board was formed in 1902. The MWB took over the assets. This included the unfinished reservoirs at Walton. The MWB continued building. Finally, the Knight Reservoir was inaugurated in 1907.
The Knight Reservoir is adjacent to its twin, the Bessborough Reservoir. Together, they cover 125.5 acres. They can hold 1,198 million gallons of water. The Knight Reservoir itself has a surface area of 20.8 hectares. Its perimeter stretches 1,800 meters. Imagine the scale of digging 1.15 million cubic meters of earth. The embankment walls have a core of puddle clay. This extends down to the blue London clay.
The inlet pipes and water discharge tower are on the north embankment. Water from the reservoir used to flow under the river to Hampton Water Works. Gravity did most of the work.
The Metropolitan Water Board managed the Knight Reservoir until 1974. After that, the Thames Water Authority took over. In 1989, the water industry was privatized. The TWA became Thames Water.
The Knight and Bessborough Reservoirs are a Site of Special Scientific Interest. This highlights their ecological importance.
Water is pumped into the reservoir from the Thames. Originally, steam engines powered the pumps. Each engine could deliver 114 million liters a day. The reservoir allows solids to settle. Sunlight helps with biological cleaning. It also provides a buffer. This maintains capacity when the river flow is low.
The water quality improves during storage.
Originally, water flowed by gravity to filter beds at Hampton. The difference in height powered hydraulic turbines. These turbines pumped river water into the reservoirs. Besides the Knight and Bessborough Reservoirs, there were four smaller reservoirs.
In the 1920s, a water treatment works was built. By 1933, it included six slow sand filters. In 1926, the steam engines were updated. In 1964, electric motors replaced them.
Today, the Knight Reservoir stands as a testament to engineering. It highlights the ever-evolving story of London’s water supply. It also shows how we balance progress with environmental care. Next time you turn on the tap, remember the Knight Reservoir.