Register a large reservoir and keep it safe

The main rules here are for England. Each other nation has its own regime, noted below.

Check whether your reservoir is covered

The Reservoirs Act 1975 applies to a large raised reservoir. That is a structure, or a lake or other area created or enlarged by artificial means, that can hold water above the natural level of any part of the surrounding land. It includes anything used or designed to contain the water or control its flow. The Act sets the size at 10,000 cubic metres, but in England it is read as 25,000 cubic metres until the lower figure is brought fully into force.

The duties fall on the undertaker. If the Environment Agency, Natural Resources Wales or a water company manages the reservoir, that body is the undertaker. Otherwise it is whoever carries on the undertaking the reservoir serves or, failing that, the owner or lessee.

A high-risk designation says nothing about how likely a failure is. You can appeal a designation to the First-tier Tribunal.

Register the reservoir

If you are building, altering or bringing a large raised reservoir back into use, tell the Environment Agency first and check whether you also need planning permission or an environmental permit.

Appoint panel engineers

Tell the Environment Agency within 28 days when you appoint or change an inspecting or supervising engineer.

Inspect and keep up the safety work

The supervising engineer can direct you to carry out visual inspections. You must also give each engineer the facilities and information they need.

High-risk owners should keep an inspection information pack that holds everything known about the reservoir. The inspecting engineer receives it before a planned inspection, and the supervising engineer must be able to reach it at any time.

Have a certified flood plan

If you do not have a plan, you need one within 12 months of the Environment Agency's letter or as it otherwise directs. Your local authority or local resilience forum draws up the off-site plan for the community, and your plan should work with it.

Report incidents

Call the Environment Agency's incident line if something could cause damage or injury, such as overtopping, a leak, slope instability, cracks, abnormal instrument readings or a landslip on the dam. A high-risk owner should also contact the supervising engineer. Once the release is under control, give the Environment Agency a preliminary report with the date, time, location and anything else important. Send a final report on the post-incident form within one year.

Know what non-compliance costs

If you fail to act, the Environment Agency can commission the work and recharge you. Under common law you can also be liable for damage a failure causes.