Guidance

Check if you need a licence to impound water

If you impound water, or plan to, you may need to apply for an impounding licence.

From:
Environment Agency
Published
31 March 2022
Last updated
17 December 2024 — See all updates

Applies to England

An impoundment is a structure within inland waters that can permanently or temporarily change the water level or flow. This includes:

  • dams
  • weirs
  • fish passes
  • hydropower turbines
  • sluices
  • penstocks
  • culverts
  • lock gates
  • retaining walls
  • flumes
  • reservoir embankments
  • temporary diversions during construction work

You must have an impounding licence before you start work on building a new impoundment structure, even in an emergency.

If an existing structure does not currently have an impounding licence, you must get one before you start work to alter or remove the structure.

There are some situations where you may not need an impounding licence.

Exemptions

You do not need an impounding licence if your activity is exempt.

The exemptions are for:

  • works constructed without a licence before 1 April 2006, except when the Environment Agency gives notice that a licence is needed
  • public authorities that manage or own waterways or harbours constructing any new impoundment, altering an existing impoundment, or obstructing or impeding the flow of inland waters while using their powers or carrying out their duties
  • impoundment authorised by a drought order or drought permit
  • structures and works authorised by legislation (for example an act of Parliament)
  • construction or alteration works authorised by a development consent order, if the Environment Agency has agreed that an impounding licence is not needed
  • when the Environment Agency gives notice requiring impoundment only for the purpose of screening or passage for eels

Low risk impounding activities

Some impounding activities have a low impact on the environment and other water users.

The Environment Agency will not normally need you to apply for an impounding licence for:

  • fish easements or passes that have formal written approval by the Environment Agency and do not significantly affect the distribution of flow over the weir
  • placing a notch in a weir to encourage fish migration
  • placing woody debris across part of the channel to diversify flows
  • flap valves that only operate during flooding
  • fixed control or passive flood prevention structures within the channel that only hold back flood water (structures with movable gates or sluices require an impounding licence)
  • small measurement structures, such as v-notch or small rectangular weirs The Environment Agency will not normally require a licence application for:
  • refurbishing a sluice
  • re-pointing (block work structures)
  • repairs (for example to expansion joint, stone pitching or bank or wall)
  • void filling (‘solid’ structures)
  • managing vegetation
  • de-silting
  • re-positioning (rock, rubble or block work bank protection structures)
  • replacing elements that do not contribute to phased replacement of the whole structure
  • re-facing
  • skimming or covering
  • blockage removal, including screen clearing
  • embankment grouting

Other activities that will not normally require a licence are:

  • works that temporarily divert water during construction or maintenance of a structure and do not affect any other water users, rights or the environment
  • impounding works or changes to the impoundment to reduce or avoid an immediate threat to human life, property or the environment during an emergency
  • any activity outside the channel, for example on top of the river banks, such as installing or maintaining bridge supports or flood defences
  • work in the river, parallel and adjacent to the bank that does not significantly narrow the channel, for example installing sheet piling, rip rap and rock revetments for erosion protection
  • installing a wave wall on an existing reservoir dam that is not intended to impound any extra water
  • increasing the height of spillway sidewalls (that does not alter the impounding level)
  • altering, moving or constructing a spillway without increasing the impounded level or changing the downstream flow regime to the detriment of the environment

Low risk impoundment checklist

If you answer ‘no’ to all of the questions on this checklist, then you are not likely to need an impounding licence. Keep a copy of this checklist for your own records. The Environment Agency may ask to see your checklist and supporting evidence which shows how you assessed that you did not need a licence.

  1. Do surveys reveal any existing abstractions, including unlicensed ones, which may be affected by the proposal?

  2. Are there any other water users or riparian rights or interests that may be affected?

  3. Will the changes cause parts of the weir to suffer significantly reduced flows?

  4. Is the proposal within, or likely to have an impact on a Site of Special Scientific Interest, Special Area of Conservation, Special Protected Area or Ramsar site?

  5. Are planned changes in river flow likely to cause significant change to invertebrate habitats?

  6. Does the proposal affect protected species (not fish) that may live at the site or elsewhere in the catchment?

  7. Are planned changes in the river flow likely to cause a significant change in the macrophyte and diatom communities?

  8. Will the proposal impact on either the up or downstream passage of fish (including eels)?

  9. Will the proposal impact on any fish spawning or nursery areas?

  10. Will the proposal cause sediment movement or deposition to be substantially altered above or below the site?

  11. Will pollutants be discharged or mobilised into the river during construction or operation?

  12. Is the proposal likely to significantly increase river turbidity or significantly alter movement of sediment?

  13. Does the scheme involve construction of a new raised reservoir with the capacity of 25,000 cubic metres or more?

  14. Will the proposal cause erosion of the river banks up or down stream?

Apply for a licence to impound water

Find out how to apply for a licence to impound water.

If you impound water without a licence when you need one the Environment Agency may take enforcement action.

Other permissions you may need

You may also need to apply to the Environment Agency for an environmental permit for a flood risk activity when you build in, over or next to main rivers. For rivers and watercourses that are not main rivers you must apply to your lead local flood authority for consent.

If you want to abstract (take) water, check if you need an licence to abstract water.

Get advice

If you are not sure if your proposal needs an impounding licence, you can get advice using the Environment Agency’s enhanced pre-application service.

Updates to this page

Published 31 March 2022
Last updated 17 December 2024 + show all updates

  1. Updated the exemption scenario for construction or alteration works authorised by a development consent order.

  2. Updated the 'Low risk impoundment activities' section to add in what these are, with a list of questions you can check against. Removed the link to the regulatory position statement 302.

  3. Updated the 'Low risk impounding activities' section to link to the regulatory position statement (RPS) 'Low risk impounding activities: RPS 302', as this now defines these activities and how to comply with the RPS.

  4. Explained if you want to alter an existing impoundment structure that does not currently have an impounding licence, you must get one before you start work to alter or remove the structure. Added a link to the flood risk activity permitting page. Clarified the information about exemptions. Clarified that you can request enhanced pre-application advice if you are unsure whether you need an impoundment licence.

  5. First published.

Sign up for emails or print this page

Contents

Related content