Reservoirs: owner and operator requirements

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

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

There are different requirements for reservoirs that hold 25,000 cubic metres or more of water above ground level (known as large raised reservoirs) and for 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 (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 don’t 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 reservoir that holds or has the potential to hold 25,000 cubic metres or more of water above ground level. This is the equivalent of 10 Olympic swimming pools.

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 a reservoir with the Environment Agency if it holds or could hold 25,000 cubic metres or more of water above ground level.

You don’t 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 (known as a panel engineer) for any reservoir that holds or could hold 25,000 cubic metres or more of water above ground level.

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 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 isn’t high risk, you’ll only need to appoint a construction engineer if you plan to make any alterations to the reservoir.

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 needs to produce a statement once a year of any observations they have made, for example of maintenance needs such as grass cutting. If your reservoir is considered high risk, you’ll need a supervising engineer appointed at all times unless the reservoir is being supervised by a construction engineer.

Inspecting engineer

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

  • 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 either of the 2 main lists:

If you have a non-impounding reservoir, you can instead appoint an engineer from the non-impounding reservoirs engineer list or from the service reservoirs engineer list.

Different arrangements apply in Scotland.

Reservoir safety

The following research about reservoir safety is on the British Dam Association’s website. You can get copies by emailing too.

  • 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

In February 2015, Defra announced that it has no plans to make further changes to the reservoir safety regulatory regime. The Reservoir safety information note (PDF, 40.1KB, 4 pages) explains this decision.

Application process for panel engineers

The Reservoirs Act 1975 requires reservoir undertakers to appoint specialist engineers from a series of panels. Engineers who want to apply or reapply to any of the panels should email their application to

Cheques for £385 made payable to ‘Defra’ should be sent to:

Reservoir Safety Team
Defra, Area 3C Nobel House
17 Smith Square

Applications for reappointment should be sent well in advance of the expiry date of an appointment to allow enough time for processing. You should apply at least 8 months before expiry. Reference documents for applicants include:

Prepare a reservoir flood plan and flood map

You should produce an on-site reservoir flood plan for any type of reservoir.

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

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

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.

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.