Reservoir Safety in Wales 2023 - 2025

Introduction

We are the enforcement authority for the Reservoirs Act 1975 in Wales. This biennial report is provided to fulfil the duty placed on us by section 3 of the Reservoirs Act 1975 to report to the Welsh Ministers every two years. This report is for the period 1 April 2023 to the 31 March 2025. Specifically, we must report to the Welsh Ministers on:

• the number of large raised reservoirs that have been registered
• the steps we have taken to ensure the undertakers—the legal term for owners and operators—of large raised reservoirs observe and comply with the requirements of the 1975 Act
• the number of large raised reservoirs for which we are the undertakers
• any steps we have taken to observe and comply with the requirements of the 1975 Act

This means we must maintain a dual role as both the enforcement authority and as an undertaker. As an undertaker, we manage a portfolio of our own reservoirs for flood management and conservation benefits. We also manage reservoirs within the Welsh Government Woodland Estate (WGWE) on behalf of the Welsh Ministers. We have clear governance separation around our two roles, and we separate this report to reflect these different responsibilities.

Our report is therefore provided in two parts:

• Part 1: Our duties as an enforcement authority to maintain the register, provide risk designations, and our work to ensure that reservoir undertakers observe and comply with the law.
• Part 2: Our work to discharge our own responsibilities as a reservoir undertaker including our work to manage reservoirs within WGWE on behalf of the Welsh Ministers.

Executive summary

There are 405 large raised reservoirs in Wales which are subject to regulation by us under the Reservoirs Act 1975. Overall, we report that, as of 31 March 2025, 40 reservoirs (9.9%) are recorded with one or more unresolved breaches in place.

The tables below show these non-compliances as the number of reservoirs and as percentages against each principal requirement of the law, in comparison with previous years. Note, a reservoir can be non-compliant for more than one reservoir activity.

Table 1: The number of reservoirs recorded as non-compliant with the Reservoirs Act 1975 on 31 March for each year shown.

Table 2: Percentage of compliance with the principal requirements of the Reservoirs Act 1975 on 31 March for each year shown.

Figure 1: The number of compliant and non-compliant reservoirs in each principal undertaker group recorded at the close of the period on 31 March 2025.

The performance around the need for inspection has occurred because of the timing of inspections at orphan reservoirs, where no owner exists. We have recorded this as non-compliance but have taken steps to ensure the required inspections are completed.

Compliance with the completion of statutory safety measures and with monitoring and record keeping is poor. Safety measures can include the requirement for investigations or surveys, and failure to comply does not subsequently equate to a reservoir dam being unsafe. They are important however and this measure indicates where the reservoir does not meet the standard expected.

We take advice from engineers on the seriousness of non-compliance, and we have used enforcement powers to require completion of safety works but we have not considered it necessary during the period to take emergency action to avert an incident.

In terms of NRW’s own performance as an undertaker, within which we include our management of reservoirs within the Welsh Government Woodland Estate, we have improved. One area for attention occurred where our compliance dipped due to over-running on safety measures at four reservoirs. This has been rectified, and we close the period reporting 100% compliance.

Our work on the reform of reservoir safety has continued and we have actively engaged with Welsh Government, along with colleagues in England from the Department for Environment, Farming and Rural Affairs and with the Environment Agency. The principal aim of this reform work is to address the recommendations made in the independent review by David Balmforth and to help an evolution of regulation that better reflects the safety of reservoirs as well as compliance with the regulations.

Definitions and acronyms used

• High-risk reservoir: a high-risk reservoir is a large raised reservoir which has been designated by us because we have determined that in the event of an uncontrolled release of water from the reservoir, human life could be endangered.
• Large raised reservoir: a large raised reservoir is a structure or area that is designed or capable of storing 10,000 cubic metres of water above the natural level of the surrounding land.
• MIOS: Measure(s) to be taken in the interests of safety are statutory recommendations given by inspecting engineers.
• Orphan: An orphan reservoir is one which has no owner and consequently there is no undertaker responsible for the structure.
• Undertaker: the person or organisation that manages or operates a reservoir, or in the absence of any activity it is the owners and lessees.
• WGWE: Welsh Government Woodland Estate.

Qualified civil engineers

An important principle of the Reservoirs Act 1975 is that the principal activities of construction, inspection, supervision, safety improvements and ultimately the decommissioning of reservoirs is done under the guidance of qualified civil engineers (QCE) with considerable experience of working on reservoirs. To perform as a QCE, an engineer must be appointed to one of four specialist panels, following recommendation by the Institution of Civil Engineers.

An All Reservoirs Panel Engineer (ARPE) can perform all roles at all reservoir types.

A Non-Impounding Panel Engineer (NIPE) can perform all roles at non-impounding reservoirs which do not directly impede a watercourse and where the inflow can be controlled.

A Service Reservoir Panel Engineer (SRPE) can perform all roles at service reservoirs which are non-impounding and built of brick or concrete.

A Supervising Engineer (SE) can act across all reservoir types but limited to the duties of a supervising engineer to monitor reservoir behaviour and provide yearly statements.

Formal terms for QCEs are given by the Reservoirs Act 1975 for the principal activities, as follows:

• Construction engineer - a QCE to design or approve and to supervise the construction or alteration of a large raised reservoir
• Inspecting engineer - a QCE appointed to carry out a periodic inspection of a large raised reservoir and to provide a report
• Supervising engineer - a QCE whose role it is to visit the reservoir at least once a year and to provide a statement to keep the undertakers advised of its behaviour and of any breach of the law.

Explanatory note on compliance percentage calculations

In this report we express the level of compliance as percentages. There are different requirements placed on undertakers depending on the risk designation of their reservoir. The percentages we use are calculated as follows:

• for activities which apply to all “large raised reservoirs” such as construction, incident reporting and decommissioning, we show compliance as the number of compliant reservoirs as a percentage of all registered large raised reservoirs
• for activities that apply only to “high-risk reservoirs,” such as inspection, supervision, monitoring, and record keeping, we calculate the compliance as the number of compliant high-risk reservoirs as a percentage of all high-risk reservoirs

In previous reports, we used the total number of large raised reservoirs as the common denominator for all percentage calculations and did not make the distinction between high-risk reservoir and undesignated large raised reservoirs. We have changed this to improve accuracy and transparency. Any references in this report to percentages in previous years for comparison purposes have been adjusted to our revised calculation.

Reservoir safety reform

In autumn 2024, Welsh Government confirmed its commitment to addressing the recommendations made by Professor Balmforth in his report into how reservoir safety is regulated (Reservoir review: part B (2020) - GOV.UK (www.gov.uk)). There are 15 recommendations and 52 sub-recommendations to be addressed.

We have actively engaged in this programme to support Welsh Government, The Department for Environment, Food and Rural Affairs (DEFRA) and the Environment Agency. The reform programme includes the development of proposals for:

• an improved approach to how the hazard posed by reservoirs may be better classified and subsequently guide the nature of mandatory safety management practices
• revised and additional specialist panels of engineers to provide increased uptake into the disciplines of reservoir engineering and improve development opportunities
• the use of a reservoir safety case and management plan to provide a clear understanding of hazards and how they are to be protected by the undertakers
• the use of civil sanctions, in addition to the current criminal sanctions, to enable a broader range of responses to breaches of the law
• modernisation of legislation

We continue to develop these proposals to enable future public consultation.

The programme of reform will emphasise that regulation needs to help assure public safety and not just compliance with the law, as reported in this document, and is therefore an important initiative in the progression of reservoir safety work.

Part 1 - Our role as the enforcement authority

Our principal duties are to:

• maintain a register of large raised reservoirs in Wales
• designate as high-risk reservoirs those we think human life could be endangered in the event of an uncontrolled release of water
• ensure reservoir undertakers observe and comply with the Reservoirs Act 1975

The register of large raised reservoirs

There are 405 large raised reservoirs recorded on the public register. The number and status of these reservoirs over the last five years are shown in Table 3

Table 3: The number and status of large raised reservoirs registered as recorded on 31 March over a five-year period.

The responsibility for reservoir safety and for legal compliance falls to the undertakers of which in Wales:

• 35% are statutory water companies
• 26% are private landowners
• 21% are managed by publicly funded bodies:
  • local authorities 10%
  • Natural Resources Wales 9%
  • national park authorities & Cadw 2%
• 18% are managed by other organisations

The undertakers may use reservoirs for many different uses as well as traditional water supply. Other uses include hydro-electric power generation, natural and heritage conservation, recreation, river regulation, flood control and general amenity.

Risk designation

We have a duty to consider the risk posed by reservoirs and to provide risk designations for them which establishes the extent of statutory inspection and supervision by engineers. On 31 March 2025, the 405 large raised reservoirs are designated as follows:

• 277 (68%) as high-risk reservoirs
• 81 (20%) confirmed to be not high-risk reservoirs
• 47 (12%) not yet designated

Risk designations are based on the flood consequences identified by mapping a breach of the dam and the loss of all the water. Those that are not yet designated are smaller reservoirs which were registered after our last dam breach flood mapping project. Further mapping is planned for 2025-26, subject to funding, to enable the remaining designations to be made.

During the reporting period, three appeals were brought by undertakers against our designations. Planning and Environment Wales (PEDW) received these appeals, but each was withdrawn before a decision was made. Consequently, the high-risk designation in each case was confirmed.

Regulated activities

We use a regulatory process which focusses on the principal minimum requirements specified by the Reservoirs Act 1975 for each of the following activities:

• construction and alteration
• supervision
• inspection
• measures to be taken in the interests of safety
• statutory maintenance
• monitoring, surveillance, and record keeping
• decommissioning, including abandonment and discontinuance

We also:

• collect post-incident reports from undertakers
• encourage and monitor the availability of flood plans

Our work over the period 1 April 2023 to 31 March 2025 for each of these activities is reported below.

Construction and alteration

100% compliance on 31 March 2025
99.5% lowest compliance during the period

We recorded two offences for the construction or alteration of a large raised reservoir without the appointment of a construction engineer. In both cases we provided advice, and an engineer was appointed by the undertaker without use of enforcement powers.

During the period we have monitored the appointments of construction engineers at 44 reservoirs. Construction engineers are appointed for several purposes. There were:

• four appointments for the construction of new large raised reservoirs
• five appointments for the alteration of existing large raised reservoirs
• thirty-five appointments for the first inspection of large raised reservoirs without a final certificate. These are predominantly for first inspection of old reservoirs recently brought into regulation as high-risk reservoirs

Eight reservoirs received a final certificate to confirm satisfactory completion of works.

Supervision

98.6% compliance on 31 March 2025
86.6% lowest level of compliance during the period

Throughout the report period we recorded 37 reservoirs with breaches of the requirement for a supervising engineer.

Ten breaches (27%) were attributed to the removal of an engineer from the Government All Reservoirs Panel. The undertakers affected by this found themselves in an unforeseen position and found it difficult to make a new appointment immediately.

In eighteen breaches (47%) undertakers failed to appoint a supervising engineer following the first-time designation of the reservoir as a high-risk reservoir. Many expressed difficulties sourcing and agreeing contracts with engineers.

Most breaches were resolved within the period. Four reservoirs remained in breach at the close of the report period on 31 March 2025 for which we have used our reserve powers to appoint supervising engineers.

• Two reservoirs are under ownership by a single undertaker and as a limited company it was dissolved in 2024. We continue to investigate the circumstances of this. Enforcement notices were issued prior to dissolution, and we used our reserve powers to appoint a supervising engineer for each reservoir. No emergency works have been required, and we maintain surveillance at the reservoirs.
• We also used our reserve powers to appoint supervising engineers at two orphan reservoirs where there is no owner to act as undertaker. Other work at these reservoirs is summarised in the section on Orphan Reservoirs.

Table 4: High-risk reservoirs where we have appointed a supervising engineer using our reserve enforcement powers as on 31 March 2025.

As a result of our appointment of supervising engineers where the undertakers have failed to do so, no high-risk reservoir is without this level of protection.

Our other work in relation to the supervision of reservoirs includes the receipt and verification of:

• 135 new or amended appointments for supervising engineers
• 281 supervising engineer statements

Inspection

99.3% compliance on 31 March 2025
97.5% lowest compliance during the period

During the reporting period, 53 reservoirs were inspected. We received inspection reports for 41 of these inspections in addition to a further 31 inspection reports outstanding from the previous period. At the end of the period 13 reports remain outstanding.

Where we have received inspection reports, the mean average time for engineers to provide them is five months, and the longest amount of time between inspection and receipt was 11 months.

For reservoir inspections where we had not yet received the engineer’s report, the time since inspection varies between 1 and 22 months, with a mean average of 6 months since inspection.

We record the engineers’ reasons for reports taking more than six months to produce. The reasons are varied but many cite large and increasing workloads on reservoir safety projects and the additional work at short notice arising from the removal of an inspecting engineer from the All Reservoirs panel.

We recorded a total of seven high-risk reservoirs where inspections were not carried out in time.

Two reservoirs, not inspected within the last reporting period, continue to be non-compliant, however the undertakers are progressing towards discontinuance and to date we have withheld from serving an enforcement notice. We continue to monitor these cases.

Four cases of late inspection relate to reservoirs due their first inspection following designation. All have been resolved without the use of enforcement notices.

We recorded one other instance of an undertaker failing to obtain an inspection report in the time required. We served an enforcement notice requiring the inspection to be made and following default of this notice we used our reserve powers to make our own appointment, and the reservoir has been inspected. Our investigation continues.

Measures to be taken in the interests of safety

92.1% compliance on 31 March 2025
85.6% lowest compliance during the period

During an inspection, the inspecting engineer may make a recommendation as to measures to be taken in the interests of safety; these are commonly termed MIOS. These recommendations are statutory requirements, and the inspecting engineer prescribes a timescale within which the MIOS must be completed.

We do not disclose the exact nature of safety works to help protect the security of reservoirs, but we report that there were 397 MIOS current during the period, spread across 110 reservoirs. The nature of these MIOS is shown below:

154 MIOS were certified as complete, with 49 (32%) of these certified later than the statutory target date provided by the inspecting engineer.

At the end of the report period:

• 243 MIOS were outstanding, across 75 reservoirs
• 81 (33%) of these, across 22 reservoirs, were overdue their target date

When MIOS are overdue, we seek the opinion of an engineer as to the seriousness of the breach to inform the action we take. We have used our reserve powers to complete MIOS works at two orphan reservoirs, described below, but we have not considered this necessary at any reservoir with a known undertaker.

Statutory maintenance

98.9% compliance on 31 March 2025
98.9% lowest compliance during the period

Recommendations made by inspecting engineers as to the maintenance of a reservoir are not often time bound because they are intended for ongoing activities. The supervising engineer provides a statement each year which reports on the status of these recommendations.

We recorded three reservoirs where timebound maintenance activities were incomplete at the end of the report period. We are also monitoring an additional 36 reservoirs where maintenance progress is less than expected.

Monitoring, surveillance, and record keeping

91.7% compliance on 31 March 2025
89.9% lowest compliance during the period

We were notified of 14 statutory Directions by supervising engineers to undertakers to carry out visual inspection for specific concerns. This brings the total number of Directions in place to 19. We received two notifications by supervising engineers of Directions not being followed at two reservoirs.

In total, we recorded breaches of the requirements for reservoir monitoring and record keeping at 28 reservoirs. There were 23 cases remaining open at the end of the report period, which we continue to monitor and seek resolution.

Discontinuance

100% compliance on 31 March 2025
100% lowest compliance during the period

Discontinuance is an alteration of the structure so that it is no longer a large raised reservoir. Two reservoirs were certified as discontinued and which were subsequently removed from the register. Four further reservoirs have a QCE appointed to design and supervise future discontinuance.

No breaches were recorded.

Abandonment

100% compliance on 31 March 2025
99.8% lowest compliance during the period

Abandonment retains the reservoir structure but prevents the reservoir from filling to any level that may pose a risk. One reservoir is recorded as being formally abandoned. The structures currently remain in place in case the reservoir is required again in the future.

A minor breach was recorded with the late submission of a certificate confirming completion of safety measures; however, the reservoir was empty at the time and presented very low risk.

Orphan reservoirs

Where there is no undertaker or owner, or we cannot identify an owner, we refer to a reservoir as being an ‘orphan.’ There are currently two reservoirs in Wales which we consider to be orphans, these are Cwm Clydach and Llyn Cae Conroy Upper and at each we have stepped in as a matter of last resort to protect public safety. We have taken the following steps using our reserve powers:

• appointed a supervising engineer
• appointed an inspecting engineer to provide a report and make recommendations
• established projects to complete MIOS

Future inspections may reveal additional work is needed and we will explore opportunities to lower the level of risk by reducing the volume or decommissioning to reduce the substantial burden of ongoing monitoring and supervision by us.

Cwm Clydach

Our project to address the ten MIOS arising from the 2021 inspection report has continued. The work required us to obtain consent from Cadw prior to starting. Completion of a substantial number of MIOS is expected over summer 2025 at which time a further inspection will be undertaken. There are recommendations included within the inspection report which we cannot perform due to limitations within our reserve powers.

The chief value of this reservoir is its dam which is a scheduled monument and a listed building. There are difficulties and additional expense in meeting the engineering standards on such a structure and long-term capital and revenue finance is needed for future construction works and ongoing surveillance. Our reserve powers do not include the power for day-to-day maintenance and deterioration is to be expected and further construction works to ensure safety in the future.

Our initial consideration of opportunities to discontinue the reservoir have been dismissed at this time. First, consent from Cadw would be needed for this. Secondly, the cost of removing substantial quantities of silt and invasive non-native species would be prohibitive.

Llyn Cae Conroy

An inspection in 2022 contained a recommendation for a single safety measure to improve protection from extreme floods. We have served notice on site to enable our reserve powers to come into force. We have appointed a consultant to prepare options for our consideration on whether to complete the MIOS or to decommission the reservoir.

Emergency flood planning

On 31 March 2025 we recorded that 82% of high-risk reservoirs had a written flood plan in place.

We expect all undertakers to prepare and maintain a flood plan which is proportionate to the inherent risk held at their reservoir. This is not required by law, and we pursue emergency planning through voluntary means. Our principal focus is to secure flood plans for all high-risk reservoirs. The research carried out as part of the reservoir safety reform programme, suggests that flood plans ought to be made a statutory requirement for high-risk reservoirs.

Post incident reporting

We recorded ten incidents at large raised reservoirs during this period. One incident included the failure of a low earth embankment dam and loss of water from an ornamental reservoir. The remainder were incidents requiring some precautionary measures to be taken. These incidents were responded to by the undertakers, and none required us to step in using emergency powers. Table 5 below list the incidents.

We are working with the Institution of Civil Engineers and the Environment Agency to produce an online database of reservoir incidents. The purpose of this is to provide better information to reservoir owners and engineers on the sorts of incidents that occur, the shortcomings found, and the lessons learnt from them. We expect this to be published online by the end of the year.

Table 5: Reservoir safety incidents recorded in Wales 2023-25.

Part 2 – Reservoirs managed by NRW

NRW has a dual role, being both the enforcement authority and a reservoir undertaker. The potential conflict of interest is minimised by separating our operational and enforcement duties at directorate level. This second part of our report describes the steps NRW Operations Directorate has taken to observe and comply with the requirements of the Reservoirs Act 1975 in our capacity as an undertaker. We include within this our work to manage reservoirs within the Welsh Government Woodland Estate.

The number, purpose and designation of these reservoirs is summarised in Table 6 below.

Table 6: The purpose and risk designation of reservoirs managed by NRW

These reservoirs are inspected and supervised by qualified civil engineers, and we maintain a programme of works to address the recommendations they may make.

Table 7 below shows the percentage of compliance for our reservoirs including those in the Welsh Government Woodland Estate.

Table 7: Summary of compliance with the Reservoirs Act 1975 recorded on 31 March 2025.

On occasion, NRW’s compliance has dipped below aspiration but overall is increasing and we ended the period recording 100% compliance. During the report period, performance dipped in the MIOS category, and the reservoirs where this occurred are described in more detail below.

Our separation of duties as regulator and as undertaker is important. We, as regulator, monitor, treat and report performance by NRW Operations the same as other undertakers.

Measures in the interests of safety

100% compliance on 31 March 2025
84.6% lowest compliance during the period

We have progressed a programme of reservoir works to address 36 MIOS across 12 high-risk reservoirs.

• 17 MIOS remain outstanding across seven high-risk reservoirs. All are within the target time limit provided by the inspecting engineer
• 13 MIOS were certified complete within the inspecting engineer’s time limit
• A further six MIOS were certified complete, but we took longer than the recommended time limit. These breaches are described below.

Further inspections are scheduled which we expect to result in additional work.

We recorded breaches of the Reservoirs Act 1975 at four reservoirs. All related to the requirement for the failure to carry into effect any recommendation as to measures to be taken in the interests of safety within the timescale given by the inspecting engineer and to obtain a certificate. All were resolved by the end date covered by this report (31 March 2025).

Whilst we do not disclose the exact nature of safety works, a summary of each case is given below.

Llyn-y-Parc

Date breach occurred: 9 July 2023
Date breach resolved: 2 August 2024

This is a reservoir managed within the Welsh Government Woodland Estate. Two MIOS both with a statutory target date of July 2023 were not completed in time. Although project design did progress, the construction works were delayed because priority and funding were given to works at other reservoir sites. The framework contractors, experienced with reservoir safety work, were also engaged on other projects. On-site work began in March 2024, and the project completed in June 2024 with formal certification confirming completion in August 2024.

Pendam

Date breach occurred: 23 October 2024
Date breach resolved: 11 November 2024

This is a reservoir managed within the Welsh Government Woodland Estate. The MIOS was to produce a flood plan. This was drafted prior to the deadline followed by some disagreement as to the content versus operational implementation, now resolved. Overdue by three weeks, the plan is also complicated by the fact there are multiple owners at the reservoir.

Cowbridge & Llanblethian flood storage area

Date breach occurred: 9 July 2023
Date breach resolved: 12 December 2024

NRW’s Operations Directorate found securing the necessary legal wayleaves across neighbouring land to be difficult and this prevented the installation of improved communication and automation at the site. Additional negotiations with BT Openreach and National Grid were needed for alternative solutions. We continued to manage the site manually. The integrity of the structure was not at risk by this failing, and we were advised by the inspecting engineer that the reservoir was “satisfactory and safe.”

Crafnant Loop flood storage area

Date breach occurred: 15 March 2024
Date breach resolved: 17 January 2025

The MIOS was recommended in the 2021 inspection report and was given a three-year period for completion by the inspecting engineer. Whilst the initial planning and design progress were completed, the programme was extended to re-evaluate the value of this asset for flood risk management purposes. The work was not completed in time, with some delay caused by the QCE being removed from the panel. A new QCE was appointed in July 2024. Following investigations and secondary inspection, the new engineer determined that the dam flood category should be reduced and that the MIOS was no longer required. We record the breach as a matter of fact because the additional consideration and decision was received after the MIOS deadline had already passed. NRW Operations Directorate is also exploring options to manage surface and flood water at the site with the local authority.

Other improvement works

Llyn Tegid

Llyn Tegid plays a vital role in regulating the river Dee, storing river water, and allowing controlled release to manage flood risk and enable abstraction for water supply. The completion of the main embankment works was well received and NRW is proud to have received the Alun Griffiths Award for Community Engagement 2023 from the Institution of Civil Engineers. This reflects the benefit of early and thorough engagement with stakeholders and our goals for the sustainable management of natural resources. A further inspection has been carried out with a focus on the sluice gates.

Llyn Llywelyn

Llyn Llywelyn, near Beddgelert, is a disused 19^th century mining reservoir situated within the Welsh Government Woodland Estate, close to Yr Wyddfa. We evaluated the value of the site which is an attraction to visitors in this popular part of Eryri. In preference to decommissioning, we completed several MIOS works to improve the site. The works comprised embankment and spillway improvements to maintain safe operation and which achieved improved access to the countryside supporting our aspirations under the Well-Being of Future Generations (Wales) Act 2015.

Staffing and training

We employ two supervising engineers in house to fulfil their statutory role and provide reservoir engineering advice.

We employ two reservoir asset inspectors that predominantly cover north and mid Wales where most of our reservoirs are located. We also have a dedicated hydrometry and telemetry specialist which has improved our recording of water levels and flows.

We have continued to provide training for our ‘reservoir keepers’ to fulfil our maintenance, monitoring and record keeping duties. Our ability to visit and check all reservoirs is regularly tested during times of flood when resources are needed widely and for long hours.

We review lessons learnt with operational staff, project managers, consultants, and contractors on an annual basis to ensure we are undertaking work to the best standard we can.

Flood plans and exercises

Our flood plans are reviewed annually to ensure they remain current. We plan for one exercise every year which includes our contractors to test how they we respond to incidents. These exercises build confidence and competence, and lessons we learn are shared with emergency responders and other professional partners as appropriate.

Incidents at NRW managed reservoirs

We recorded three incidents during the report period.

• In November 2024, a tidal sluice gate failed allowing an ingress of water during high tides and reducing the capacity of the flood storage area.
• In December 2024, backflow through a surface water outfall was observed during a wider flood incident and causing increased flooding on the road behind the structure. Two pumps were already on site as per the usual flood response procedure, but two additional pumps were mobilised to site to assist. Additional maintenance of the flap valve was carried out.
• In January 2025, a spillway channel suffered scour damage. Repairs were conducted to prevent further damage to the channel.

Details of these incidents are recorded and ready for sharing via the new incidents database due to be published on the internet in autumn 2025. These are also included in Table 5 above, on incidents at all reservoirs.

Summary

During the two year period covered by this report, compliance with the Reservoirs Act 1975 has remained high, with most key indicators showing an improvement in compliance. This is particularly encouraging because reservoirs which were designated as high-risk reservoirs have been through their first inspections and undertakers have demonstrated substantial efforts to implement the requirements of the law.

Our work to maintain orphan reservoirs, and to step in at two reservoirs following the dissolution of a limited company have caused us to use our reserve powers. However, we have not needed to use any emergency powers to avert an incident occurring at any reservoir. We take advice from engineers when we make such decisions.

We actively participate in the reservoir safety reform programme and will continue to do so to help Government shape future policy.

We continue to pursue full compliance with the law. Our approach is linked to the risks posed and the programme of reservoir safety reform will bring additional benefits to focus effort where it is needed.