Gerlan Hydro Limited, Sir Richard Arkwright's Masson Mills, 41 Derby Road, Matlock Bath, Derbyshire, England, DE4 3PY

Author: Alex Cowell, Permitting Officer (Water Resources)
Application numbers: PAN-021620 & PAN-021621
Licence numbers: N/A
NRW Region: North
Date of Application: 31/03/2023

Applicant details: Gerlan Hydro Limited, Sir Richard Arkwright's Masson Mills, 41 Derby Road, Matlock Bath, Derbyshire, England, DE4 3PY

Summary of the proposal: The Agent, Derwent Hydroelectric Power Limited, have applied on behalf of Gerlan Hydro Limited for a new transfer abstraction licence and a new impoundment licence for a Hydroelectric Power (HEP) scheme on the Afon Cenllusg.

The scheme would be used to supplement an existing HEP scheme which has two separate intakes (a double intake) on the Afon Llafar and Afon Caseg, regulated under licences 23/65/18/0029 (a joint abstraction licence for both the Caseg and Llafar intakes), WA/065/0018/001 (Caseg impoundment licence) and WA/065/0018/005 (Llafar impoundment licence).

Water would be transferred from a new intake structure at SH 64634 64994 on the Afon Cenllusg and discharged upstream of the existing Afon Llafar intake at SH 64815 65400, into a new channel, which would have a length of over 30 metres before joining the Afon Llafar. The purpose of the water transfer would be to augment the existing HEP scheme by topping up the amount of water in the Llafar during periods when the turbine is not generating at full power, or not at all but could be with the additional top-up. The proposed abstraction would create a 1,150m depleted reach.

The following maximum abstraction rates are proposed: 74 litres per second (l/s), 266.4 cubic metres per hour (m³/hour), 6,393.6 cubic metres per day (m³/day) and 2,333,664 cubic metres per year (m³/year).

The applicant applied for a Zone 3 abstraction regime with a 70% take of available flow above a minimum Hands off Flow (Hof) of Q95 (low flow protection), and a maximum abstraction rate of 0.85 x Qmean, which would be controlled by a weir structure and orifice plate situated in the outfall pipe.

The abstraction would be secured by an impoundment structure, including the following:

• 10 millimeter (mm) intake ‘overspill’ screen
• A flow split with a 70% take of available flows and 30% residual flow.
• HoF notch
• Fish easement steps and plunge pool (with overall depth of 382mm)
• Eel tiles

The abstraction would be controlled by means of an intake structure as well an automated valve, flow monitoring device and orifice plate on the outfall. The valve would be set to remain closed except within a specified range of the Afon Llafar river levels, to ensure abstraction from the Cenllusg only takes place when the Cenllusg water could be used for power generation.

Case history:  

Justification of requirements and water efficiency: NRW Hydropower Guidance for Zone 1 HEP schemes specify a maximum abstraction rate of 1.3 times Qmean flows to ensure high flow protection. The proposal for a Zone 3 abstraction regime would reduce flows within the depleted reach beyond those considered acceptable under NRW hydropower Guidance. NRW consider it is likely that abstraction would occur from the Afon Cenllusg at times when there would be insufficient flow with which to generate hydroelectric power. Therefore, NRW does not consider the quantities of water applied for or the water efficiency to be fully justified or reasonable.

Water Framework Directive status and water availability: The detailed WFD assessment concluded that there is a risk of deterioration of the waterbody status of multiple waterbodies and that the project has potential to conflict with the multiple water body mitigation measures either now or in future.

Impact assessment of proposal: NRW do not consider the maximum abstraction rates applied for to be protective of high flows, or the flow split to be protective of low flows. Therefore the current proposal would reduce flows within the depleted reach created downstream beyond those considered acceptable under NRW Hydropower Guidance. There are concerns around total length of river that would be impacted by reduced flows being greater than 50% for the watercourse, plus in combination / cumulative impacts from the scheme alone. The reduced flows could impact on hydromorphology, water quality, biology and fish elements.

The above concerns regarding impacts on flow could impact on the following features present within the vicinity of the proposal:

• Ecology: Wet heath, blanket bog and deep peat.
• Fisheries: brown trout, eels and sea trout.

The proposal could result in impacts to water quality elements as follows: Any impacts to temperature are anticipated to be localised to the proposal, within the depleted reach; whilst any impacts to water clarity from reduced sediment transport could impact the depleted reach and downstream of the proposed discharge. Outstanding concerns regarding the risk of cross-catchment transfer of water could further impact on water quality.

NRW still have a number of outstanding concerns with the function of the proposed fish pass and eel pass.

NRW have been unable to rule out adverse effect on site integrity to the Eryri / Snowdonia Special Area of Conservation (SAC).

NRW consider the proposal likely to damage Eryri / Snowdonia Site of Special Scientific Interest (SSSI).

Statutory Consultation: Statutory external consultation and notification sent to Snowdonia National Park Authority on 07/07/2023 and Dŵr Cymru Welsh Water on 14/07/2023 respectively.

External Representations: In accordance with Water Resources Act 1991 (as amended by the Water Act 2003), the application was advertised in The Cambrian News on 17/07/2023 and on the NRW website. No representations were received regarding the applications.

Protected Rights: No protected rights were identified as being at risk of derogation as a result of the variation. No lawful users were identified as being at risk of being impacted as a result of the applications.

Costs/ Benefits:

Biodiversity and sustainable development: Significant concerns have been raised regarding impacts on biodiversity which NRW have been unable to address therefore the proposal is not considered sustainable.

Social and Economic welfare of rural communities: No adverse effects upon the social and economic well-being of local communities in the rural area are perceived as a result of this proposal

Sustainable Management of Natural Resources: We are satisfied that this decision is compatible with our general purpose of pursuing the sustainable management of natural resources in relation to Wales and applying the principles of sustainable management of natural resources.

Conclusion and recommendation: NRW recommendation recommend refusal of the applications for the following reasons:

1. NRW do not consider the proposal to be in line with NRW HEP Guidance flow standards which are designed to protect the environment at low and high flows, meaning, the proposal would impact on ecology, fisheries and water quality.
2. NRW do not consider the proposal has sufficient justification of requirements and water efficiency.
3. NRW have been unable to rule out adverse effect on site integrity to the Eryri / Snowdonia Special Area of Conservation (SAC).
4. NRW consider the proposal likely to damage Eryri / Snowdonia Site of Special Scientific Interest (SSSI).
5. NRW have been unable to rule out the risks associated with an open Cross Catchment Water Transfer.
6. NRW have been unable to rule out the risk of deterioration of WFD waterbody status / prevention of meeting the WFD objectives of multiple waterbodies. 

Contact the Permitting team responsible for this decision:

Email: permittingconsultations@naturalresourceswales.gov.uk

Or write to:

Water Resources Team Leader
Permitting Service
Natural Resources Wales
Welsh Government Offices
King Edward VII Avenue
Cardiff
CF10 3NQ