Guide
Register a large raised reservoir
How new reservoir undertakers register a large raised reservoir with the Environment Agency, Natural Resources Wales, SEPA or DfI. Covers the capacity threshold, the 28-day window that starts on the final certificate, and the information you must give the enforcement authority.
When you must register
If you have built, enlarged or taken over a structure that holds water above the natural level of the surrounding land, you may be the undertaker of a large raised reservoir. The undertaker is the person or organisation legally responsible for the reservoir, and registration is your first statutory duty.
You must register the reservoir with your enforcement authority once it crosses the capacity threshold for your nation. The threshold and the lead authority are different in each part of the UK.
The 28-day window starts at the final certificate
The most common compliance failure is missing the registration deadline because undertakers do not know when the clock starts. In England and Wales, the 28-day period runs from the date your construction engineer issues the final certificate under the Reservoirs Act 1975 - not from the date the reservoir first impounded water, and not from the date you took ownership.
Diary the date as soon as the construction engineer signals the certificate is imminent. If you only receive the certificate by post, treat the date on the certificate as day one and submit the registration well inside the window.
Information you need to give the authority
Each authority publishes its own registration form, but the information they require is broadly the same. Gather this before you start so you can register inside the statutory window:
- The reservoir's name, location and Ordnance Survey grid reference
- The capacity above the natural level of the surrounding land, in cubic metres
- Whether the reservoir is impounding, non-impounding or a service reservoir
- The name and address of the undertaker (and any joint undertakers)
- The construction engineer's name, panel category and the final certificate they issued
- The supervising engineer you have appointed (or are appointing) to take over after registration
- Any preliminary certificate already issued, and the date the reservoir first impounded water
Keep copies of everything you submit. You will need them for the first supervising engineer's statement and for every later inspection.
Construction, enlargement and abandonment notices
Registration is not a one-off event. You must also notify the enforcement authority when you start to construct or enlarge a reservoir, when capacity changes take it across the threshold, and when you decide to abandon or discontinue use. Notice obligations sit alongside the registration duty and run on their own deadlines.
Failing to register is a criminal offence
<p>The Reservoirs (Scotland) Act 2011 and the Reservoirs Act (Northern Ireland) 2015 carry equivalent offences for controlled reservoirs in those nations.</p>
What to do next
Once registration is acknowledged by the authority:
- Confirm your supervising engineer appointment in writing and notify the authority of the appointment
- Set up a records system for certificates, statements, inspection reports and correspondence
- Diary the next key dates: the first supervising engineer's annual statement, and the 10-year inspection deadline
- Read the wider duty set in the related guide on reservoir registration and safety inspections so you understand the full undertaker regime
If you are unsure whether your structure crosses the threshold, ask the enforcement authority for an informal view before you commit to registration. Authorities prefer early contact to retrospective enforcement.