Reservoir safety

Blithfield Reservoir
We have reservoirs at Blithfield and Chelmarsh and we’d love you to visit your local site, but please, stay out of the water.

Not everyone knows reservoirs are dangerous. Reservoirs may look inviting, especially on a hot day, but they are about the worst possible places to take a swim. According to the National Water Safety Forum, during 2017, 255 people lost their lives in open water due to accidental causes.

There are many dangers associated with reservoirs and we are keen to educate all of our customers, so that they can enjoy our open spaces in safety.

Cold water shock

Even water as warm as 25°C can cause hyperventilation leading to drowning.

At 15°C blood is diverted to vital organs causing a strain on the heart and failure of co-ordination due to muscle tensioning, meaning that even strong swimmers can be unable to reach the shore or grasp throw lines.

Some reservoirs remain cold all year round, while others may have a variable temperature profile, which means that parts remain cold all year round. This may not be obvious to a visitor or observer from the bank side.

Localised currents

Reservoirs contain machinery and pipework beneath the surface. This can start without warning and generate currents that can act as a draw on a swimmer.

Deep water

This might seem obvious but some reservoirs are very deep and may have shelves or areas, where the depth changes suddenly. This may not be apparent from the shore.

Mud and silt

There may be an accumulation of silt on the bottom of the reservoir. This can be a particular hazard when jumping in, as it can trap swimmers’ feet preventing them from resurfacing.


There may be submerged branches, plants or other hazards that can trap or entangle a swimmer.

Blue-green algae

Some reservoirs are prone to blue-green algae. These are naturally occurring but toxic organisms that can cause serious illness to humans and animals. Contact and ingestion can cause abdominal pain, vomiting, diarrhoea, skin rashes, eye irritation and allergic reactions. Very severe contact and reactions can cause liver injury and death.

Access and egress

Dams, walls and other manmade structures around the bank side can be slippery and lead to a person falling into the reservoir. There may be concealed or hard objects beneath the surface causing a risk of injury.

In some areas the banks may be steep, sheer or slippery. This can prevent a person from getting out of the reservoir.


Whilst their geographical setting is often a large part of their appeal as places to visit, it also presents challenges when emergency services are required. We would recommend that people do not place themselves in danger.

Stay out of the water.