Reservoirs: owner and operator requirements

How to register a reservoir, appoint a panel engineer, produce a flood plan, prepare an inspection information pack and report an incident.

Applies to England

You must meet certain requirements if you own or operate a reservoir, or intend to build one.

A large raised reservoir holds or has the potential to hold 25,000 cubic metres of water above ground level. This is about 10 Olympic size swimming pools.

There are different requirements for:

  • large raised reservoirs
  • reservoirs that hold less than 25,000 cubic metres of water above ground level

There are also extra requirements for reservoirs that the Environment Agency decides are high risk. These are reservoirs where an uncontrolled release of water could put people’s lives at risk. The Environment Agency will tell you if your reservoir is high risk after you’ve registered it.

You could be prosecuted if you do not comply with these requirements.

Build or modify a reservoir

You must tell the Environment Agency if you intend to build, bring back into use or alter a large raised reservoir.

Check also if you need planning permission or an environmental permit. Whether you need one or both depends on the type of reservoir and its intended location.

Register a reservoir

You must register all large raised reservoirs with the Environment Agency.

You do not have to register a reservoir with a capacity of under 25,000 cubic metres of water above ground level.

Whether you need to register your reservoir or not, you must follow Health and Safety Executive regulations and local council building regulations.

What to register

You’ll need to provide the:

  • name of the reservoir
  • grid reference - you can find this on the Ordnance Survey map
  • name and address of the reservoir owners or operators
  • date construction was completed
  • height of dam (the level in relation to the surrounding ground levels)
  • level of the top of the dam (the level relative to the ordnance datum) and top water level
  • capacity of dam
  • water surface area
  • name and address of the panel engineers
  • list of any certificates issued by panel engineers
  • date when the next inspection is due

You also need to state which type of reservoir you have:

  • impounding (blocks the natural flow of a river or drainage from an area)
  • non-impounding (filled by pumping water or by piped inflow of water)

How to register

To register, email or write to:

Reservoir Safety Team 
Environment Agency 
Manley House 
Kestrel Way 
EX2 7LQ 

You need to update the Environment Agency with any change to your reservoir. To access the register (for example to check your entry is correct), you’ll need to write, email or call the Environment Agency and ask for a copy of the register.

When to appoint a panel engineer

You must appoint a qualified civil engineer for any large raised reservoir. A qualified civil engineer is known as a panel engineer.

There are 3 types of panel engineer:

  • construction engineer
  • supervising engineer
  • inspecting engineer

If your reservoir is considered high risk, you’ll have to appoint a supervising engineer and an inspecting engineer. The exception to this is if you plan any alterations to the reservoir. In this case, you need to appoint a construction engineer rather than a supervising engineer.

If your reservoir is not high risk, you have to appoint a construction engineer if you plan to make any alterations to the reservoir. You will also need to appoint a supervising engineer to help to prepare an on-site emergency flood plan.

Construction engineer

Appoint a construction engineer during the design, construction or modification of the reservoir.

Supervising engineer

Appoint a supervising engineer to supervise a built reservoir. The supervising engineer must produce a statement once a year of their observations. This may include maintenance needs such as grass cutting. If your reservoir is considered high risk, you’ll need to appoint a supervising engineer at all times unless it is supervised by a construction engineer.

The supervising engineer will also help to prepare an on-site emergency flood plan for both high risk and not high risk reservoirs and certify that the plan meets legal requirements.

Inspecting engineer

Appoint an inspecting engineer to carry out an inspection at least once every 10 years. The inspecting engineer needs to:

  • produce a report and certificate of their inspection
  • identify any safety measures that need to be carried out, and set a deadline
  • certify that recommended safety measures have been carried out

You must carry out any safety measures identified by your inspecting engineer within the deadline they set.

How to appoint a panel engineer

You can choose an engineer from the:

Different arrangements apply in Scotland.

Reservoir safety

The following research about reservoir safety is on the British Dam Society’s website:

  • post-incident reporting system for UK dams February 2007
  • engineering guide to emergency planning for UK reservoirs June 2006
  • interim guide to quantitative risk assessment for UK reservoirs May 2006
  • floods and reservoir safety (FEH/FSR) - revised guidance for panel engineers June 2004
  • early detection of internal erosion - feasibility report November 2003
  • vulnerability of UK dam embankments to increased direct rainfall on their surfaces January 2003
  • climate change impacts on the safety of British reservoirs January 2002
  • sedimentation in storage reservoirs February 2001

You can also get copies of reservoir research safety by emailing

Application process for panel engineers in England and Wales

Defra appoints panel engineers under the Reservoirs Act 1975. If you want to apply or reapply to be a panel engineer in England and Wales, the application forms and guidance are available on the Institution of Civil Engineers’ (ICE) website.

Apply in Scotland

If you’re also applying to a panel in Scotland at the same time as England and Wales, you must complete an additional form.

Prepare a reservoir flood plan and flood map

It is a legal requirement for all undertakers to prepare an on-site emergency flood plan for all large raised reservoirs in England.

There are legal duties for engineers relating to these flood plans.

Owners and undertakers must keep plans under review and test them as advised by a reservoir panel engineer.

There’s a flood plan template you can use or you can create your own. Your plan needs to include details of how you will:

  • seek to prevent the dam from failing
  • contain and reduce the consequences of dam failure

Read Reservoir panel engineers responsibilities: on-site emergency flood plans.

Read Reservoir owner and undertaker responsibilities: on-site emergency flood plans.

Local councils are responsible for co-ordinating off-site plans for reservoir flooding and ensuring communities are well prepared. Off-site plans set out what the emergency services will do to warn and protect people and property if a dam or reservoir were to fail.

Reservoir flood maps

Reservoir flood maps show the impact that an uncontrolled release of water could have if a dam or reservoir failed.

You can consult the Environment Agency’s reservoir flood map.

Prepare an inspection information pack for your reservoir

Owners and operators of high risk reservoirs in England should prepare an inspection information pack. The pack should:

  • contain all relevant and available information for the reservoir
  • be provided to the inspecting engineer in advance of a planned inspection
  • be easy to access during an emergency
  • be accessible to the supervising engineer at all times

Read Reservoir owners and operator guidance: inspection information pack

Report an incident

You may be held responsible for any damage or injury caused due to a sudden uncontrolled release of water.

You must call the Environment Agency incident line if your reservoir is registered and there’s an incident that could result in damage or injury.

Examples of incidents are:

  • water going over the top of the dam (‘overtopping’)
  • a leak
  • slope instability
  • cracks in the dam
  • instrumentation readings that show abnormal movement in the dam
  • material failure (for example landslip down an embankment of a dam)
  • pollution

If your reservoir is high risk, you should contact your supervising engineer. If that’s not possible, you should contact your inspecting engineer.

Once the release of water is under control, you must give the Environment Agency a preliminary report of the incident. Your report must contain:

  • the date and time of the incident
  • the location of the reservoir
  • any other facts you consider important (for example what you did, who you informed)

Within one year of the incident, you must send the Environment Agency a final report using the post-incident report form.

Published 17 June 2014
Last updated 14 July 2022 + show all updates
  1. Removed link to obsolete Reservoir safety information note (February 2015).

  2. Reservoir inspection information pack section and link to new guide added.

  3. All large raised reservoirs in England must have a flood plan, and must consult with an engineer.

  4. How to appoint a panel engineer section updated to clarify which panel list to use for each type of engineer and reservoir.

  5. Updated the application process for panel engineers in England and Wales. Included a link to the application process on the Institution of Civil Engineers’ (ICE) website and removed any content from this guide that's on the ICE website.

  6. Link to reservoir safety guide removed. The guide has been removed as part of the Defra Smarter Guidance Project.

  7. All information in the Reservoir Safety and Application process for panel engineers sections moved to this guide from

  8. Added link to Scotland rules:

  9. Added line "Different arrangements apply in Scotland and they're changing from April 2016."

  10. Corrections to responsibilities for on-site and off-site plans and service reservoirs engineers added for appointing for non-impounding reservoirs.

  11. First published.