NatureScot Objection – Updated

This response should be read alongside the response dated 11th November 2025 which advised on the implications for Urquhart Bay Woods SAC and Ness Woods SAC. We have now added details from Annex A which details the impacts and further information required.

1. Summary

• River Moriston Special Area of Conservation (SAC): This proposal could affect internationally important natural heritage interests and we therefore object to this proposal until further information is provided. This will enable us to carry out an appraisal of these effects and help you determine this proposal. Even with this additional information, there is a risk that it may not be possible to show with the certainty required by the Habitats Regulations that the conservation objectives of this SAC will not be undermined.

• North Inverness Lochs Special Protection Area (SPA): There are natural heritage interests of international importance on the site, but our advice is that these will not be adversely affected by the proposal. Annex A contains details of our appraisal on this and other Slavonian Grebe SPAs relevant to this proposal.

• Background

At your request, our appraisal below is based on the proposal as described in the application, including the off-site seasonal variable weir at Dochfour the applicant proposes as mitigation for significant effects associated with water level variation in Loch Ness and downstream flows in the River Ness. The weir is not part of this application and has not yet been subject to a separate application. We understand it will be applied for by a third party who is yet to be identified. For clarity, we have not assessed the implications of Glean Earrach without the variable weir.

As previously advised in our response of 11th November, guidance on Habitats Regulations Appraisal (Ref 1) states that competent authorities must be sure that mitigation will be effective at the time they give their permission and that ‘each mitigation measure must be described in detail, with an explanation based on scientific evidence of how it will eliminate or reduce the adverse impacts which have been identified. Information should also be provided of how, when and by whom they will be implemented, and what arrangements will be put in place to monitor their effectiveness and take corrective measures if necessary’.

Therefore, in order to conduct an HRA of this proposal the competent authority requires sufficient detail on the proposed weir to assess the implications for all the European sites that could be affected and determine whether it can be concluded with certainty and beyond reasonable scientific doubt that there will be no adverse effect on the sites’ integrity. In addition the competent authority will need to be assured that the necessary legal and stakeholder agreements will be in place, and that the weir is consentable, to provide certainty that the required mitigation will be implemented.

3. Appraisal of the impacts of the proposal and advice

The proposal is to build a new pumped storage hydro (PSH) scheme near Loch Ness, centred on national grid reference NH 45255 22395, about 9.5 km south of Drumnadrochit and 6.5 km north of Invermoriston.

The proposed development will have a capacity of 1,800 MW. The upper reservoir, the Headpond, is at Loch nam Breac Dearga which is about 480 m above sea level with Loch Ness as the Tailpond. The development has underground and over ground components, including the main Power Cavern Complex, dry and wet tunnels, access tracks and control works.

The proposal also outlines future works to apply for a variable weir as part of the mitigation package. This is not part of this application and has yet to be applied for.

The project could affect Urquhart Bay Woods SAC, Ness Woods SAC, North Inverness Lochs SPA, River Moriston SAC and Moray Firth SAC. Our advice in relation to Urquhart Bay Woods SAC, Ness Woods SAC and Moray Firth SAC is contained in our response dated 11th November 2025. This response covers North Inverness Lochs SPA and River Moriston SAC.

These sites’ status means that the requirements of the Conservation (Natural Habitats, &c.) Regulations 1994 as amended (the ‘Habitats Regulations’) apply. Consequently, Energy Consents Unit (ECU) is required to consider the effect of the proposal on the SAC and SPA before it can be consented (commonly known as Habitats Regulations Appraisal). The NatureScot website has a summary of the legislative requirements (https://www.nature.scot/doc/legislative-requirements-european-sites )’.

The applicants have carried out an assessment of impacts on North Inverness Lochs SPA and River Moriston SAC in their shadow Habitats Regulations Assessment (HRA). We generally agree with the conclusions set out in the assessments for North Inverness Lochs SPA.

1. River Moriston SAC

This response supersedes our partial advice in relation to this SAC in our response of 11th November 2025.

The SAC is designated for Atlantic salmon and freshwater pearl mussel and lies approximately 8km south-west of the proposed outfall/ intake. Our advice is that this proposal is likely to have a significant effect on the Atlantic salmon and freshwater pearl mussel qualifying interests of the River Moriston SAC.

Consequently, Energy Consents Unit, as competent authority, is required to carry out an appropriate assessment in view of the site’s conservation objectives for the qualifying interests. To help you do this, we propose to carry out an appraisal to inform your appropriate assessment.

To enable us to carry out this appraisal, further information is required.

The information submitted does not demonstrate that the proposal can be constructed and operate without undermining the site’s conservation objective to restore the population as a viable component of the site, because of four impact pathways which could delay salmon migration and cause additional mortality:

• Noise, disturbance and loss of access to fish passes during construction of the proposed Dochfour seasonal variable weir impeding migration

• Changes to water levels in Loch Ness because of the operation of (a) the scheme and (b) the proposed seasonal variable weir impeding migration

• Changes to winter flow regime in the River Ness, including an increased rate of water level change, impeding salmon migration up and down river

• Acoustic fish barrier proposed between weir and canal impeding salmon migration

In addition, the information submitted does not demonstrate that the proposal can operate without undermining the site’s conservation objective to restore the habitats supporting Atlantic salmon within the site and availability of food, because of the following impact pathway:

• Changes to the water level regime in Loch Ness affecting salmon spawning habitat in the lower reaches of the River Moriston

Further information is therefore required to demonstrate:

1. how access to the fish pass, smolt chute and sluice, or temporary alternative structures, will be maintained during construction of the variable weir and how disturbance will be managed to ensure upstream and downstream salmon passage at the weir is unimpeded. This should demonstrate that there will be appropriate attractant flows, that water depths and velocities will be passable by salmon at all appropriate life cycle stages, and that disturbance will not result in salmon avoiding the area.

b)(i) the design of the new weir and fish pass(es) will allow appropriate attractant flows, water depths and velocities to be passable by salmon at all the relevant life cycle stages and times of year for each structure based on known attractant flows, swimming capabilities etc.

(ii) the changes in water levels and flows will not increase the number of smolts exiting Loch Ness via the Caledonian Canal (in which they are likely to perish), rather than the River Ness.

Evidence should be based on transparent and justified realistic worse case scenarios for water levels and flows at, around and over/through the weir and lock gates, considering the cumulative effects of all Loch Ness water users and the effects of climate change.

c) How the predicted changes to the flow regime in the River Ness will affect migrating Atlantic salmon at all life cycle stages, based on realistic worse case scenarios. This should include an assessment of effects known to be associated with hydropeaking, including stranding and associated mortality caused by increased predation; habitat alteration and loss caused by the repeated wetting and dewatering of the river bed; physiological stress and reduced growth through forcing fish to repeatedly move to seek shelter; and impeding migration. This assessment could usefully be based on the approach set out in Bakken et al (2023) (Ref2), using selected criteria which match the River Ness most closely. The assessment should also specify the proposed ramping rate and demonstrate how this will be managed to avoid adverse effects on migrating salmon (see Alfredsen et al 2022) (Ref3).

d) the effects of the proposed acoustic barrier on salmon adults and smolts will not extend towards the weir in a manner which discourages or prevents access to the proposed new fish passes.

Alternatively or in addition, the applicant may wish to review in more detail based on evidence from elsewhere whether an acoustic barrier in this location is likely to be effective in delivering the intended benefits and worth including in the proposal.

e) whether any salmon spawning habitat in the lower reaches of the River Moriston will be adversely affected by the operation of the proposed development and proposed variable weir alongside the other consented and proposed schemes in Loch Ness.

Annex A contains full details and our rationale for these requirements. We would be pleased to advise on draft approaches to demonstrating these points. Once the information above has been provided, we will be able to give further consideration to this proposal. Even with the additional information requested above, there is a risk that it may not be possible to show with the certainty required by the Habitats Regulations that the conservation objectives of this SAC will not be undermined.

Annex A also contains details of modifications and conditions required to avoid other potential impact pathways undermining the conservation objectives for this SAC.

If you require any further information on this letter please contact Corrina.mertens@nature.scot or Debbie.greene@nature.scot

The advice is provided by NatureScot, the operating name of Scottish Natural Heritage

References

1. https://op.europa.eu/en/publication-detail/-/publication/11e4ee91-2a8a-11e9-8d04-01aa75ed71a1

2. Bakken, T.H., Harby, A., Forseth, T., Ugedal, O., Sauterleute, J.F., Halleraker, J.H. & Alfredsen, K. (2023). Classification of hydropeaking impacts on Atlantic salmon populations in regulated rivers. River Research and Applications, 39(3), 313–325. https://doi.org/10.1002/rra.3917

3. Alfredsen, K., Juárez-Goméz, A., Kenawi, M.S.R., Graf, M.S. & Saha, S.K. (2022). Mitigation of environmental effects of frequent flow ramping scenarios in a regulated river. Frontiers in Environmental Science, 10 -2022. https://doi.org/10.3389/fenvs.2022.944033

Annex A

Appraisal of the impacts of the proposal and advice

Our advice is based on the documentation submitted including the proposed seasonal variable weir, which is proposed to be applied for later.

1. European sites

The project could affect the River Moriston SAC and North Inverness Lochs SPA (plus a number of other SPAs protected for Slavonian Grebe). We submitted our advice on the implications for Ness Woods SAC, Urquhart Bay Woods SAC and Moray Firth SAC on 11th November 2025.

The sites’ status means that the requirements of the Conservation (Natural Habitats, &c.) Regulations 1994 as amended (the ‘Habitats Regulations’) apply. Consequently, Energy Consents Unit is required to consider the effect of the proposal on the SAC and SPA before it can be consented (commonly known as Habitats Regulations Appraisal). The NatureScot website has a summary of the legislative requirements (https://www.nature.scot/doc/legislative-requirements-european-sites )’.

1. River Moriston SAC

This SAC is designated for Atlantic salmon and freshwater pearl mussel and lies approximately 8km south-west of the proposed outfall/ intake. For part of their lifecycle, freshwater pearl mussel are dependent upon a healthy population of salmon which act as host species. Atlantic salmon smolts from the River Moriston migrate through Loch Ness, and the River Ness, to spend a year or more at sea before returning as adults to spawn in their natal river. Elements of the scheme that could affect the water environment in Loch Ness, and/or the Rivers Moriston and Ness, therefore have the potential to affect both qualifying interests.

The population of Atlantic salmon in this SAC is in unfavourable condition, with suboptimal and declining resilience to threats and pressures. Nationally, Atlantic salmon in Great Britain have recently been assessed as being ‘Endangered’ and threatened with extinction at the regional level. In the Moray Firth, recent research indicates that around half of the Atlantic salmon smolts in the overall catchment are being lost during their downstream migration before they reach the sea. Of the seven river catchments involved in this study, the Ness Catchment, of which the River Moriston is a component, had the lowest survival percentage of smolts reaching the sea at just 18% across the three study years.

Freshwater pearl mussels are also in unfavourable condition at this site due to poor recruitment and the small size and aged status of the population, especially in the upper reaches of the river.

Our advice is that this proposal is likely to have a significant effect on the Atlantic salmon and freshwater pearl mussel qualifying interests of the River Moriston SAC because of the following impact pathways:

Atlantic salmon

Construction impacts

1. Salmon may become trapped during construction and dewatering of the coffer dam at the lower control works

2. Increased sedimentation / turbidity (non-toxic) in areas adjacent to the lower control works during construction

3. Risk of contamination (toxic) from fuel / chemical leakages / and concrete spills at the lower control works during construction

4. Risk of noise disturbance from heavy machinery, sediment movement, temporary cofferdam during construction at the lower control works

5. Noise, disturbance and loss of access to fish passes during construction of the proposed Dochfour seasonal variable weir impeding migration

6. Risk of sedimentation and pollution during construction of the proposed variable weir

Operational impacts

7. Intake flow attracting downstream migrating salmon smolts and/or kelts

8. Salmon may become impinged on intake screen during periods of abstraction

9. Capture of salmon smolts at the intake during periods of abstraction

10. Outlet flow attracting adult salmonids migrating upstream

11. Changes to the thermal regime in Loch Ness affecting salmon growth and survival, and food supply

12. Reduced productivity of the littoral zone as a consequence of changes to the water level regime in Loch Ness

13. Changes to water levels in Loch Ness because of the operation of (a) the scheme and (b) the proposed seasonal variable weir impeding migration

14. Changes to winter flow regime in the River Ness, including an increased rate of water level change, impeding salmon migration up and down river

15. Acoustic fish barrier proposed between weir and canal impeding salmon migration

16. Changes to the water level regime in Loch Ness affecting salmon spawning habitat in the lower reaches of the River Moriston

Freshwater pearl mussel

1. Impacts on the population as a consequence of impacts to the Atlantic salmon host species

Consequently, Energy Consents Unit, as competent authority, is required to carry out an appropriate assessment in view of the site’s conservation objectives for the qualifying interests. To help you do this, we propose to carry out an appraisal to inform your appropriate assessment.

1. Atlantic salmon

The information submitted does not demonstrate that the proposal can be constructed and operate without undermining the site’s conservation objective to restore the population as a viable component of the site, because of four impact pathways which could delay salmon migration and cause additional mortality:

• Noise, disturbance and loss of access to fish passes during construction of the proposed Dochfour seasonal variable weir impeding migration

• Changes to water levels in Loch Ness because of the operation of (a) the scheme and (b) the proposed seasonal variable weir impeding migration

• Changes to winter flow regime in the River Ness, including an increased rate of water level change, impeding salmon migration up and down river

• Acoustic fish barrier proposed between weir and canal impeding salmon migration

In addition, the information submitted does not demonstrate that the proposal can operate without undermining the site’s conservation objective to restore the habitats supporting Atlantic salmon within the site and availability of food, as a result of the following impact pathway:

• Changes to the water level regime in Loch Ness affecting salmon spawning habitat in the lower reaches of the River Moriston

Further information is therefore required to demonstrate:

Information	Reason
a) how access to the fish pass, smolt chute and sluice, or temporary alternative structures, will be maintained during construction of the variable weir and how disturbance will be managed to ensure upstream and downstream salmon passage at the weir is unimpeded. This should demonstrate that there will be appropriate attractant flows, that water depths and velocities will be passable by salmon at all appropriate life cycle stages, and that disturbance will not result in salmon avoiding the area.	To ensure migration of salmon from the River Moriston SAC is not impeded by noise, disturbance or loss of access to fish passes during construction of the proposed Dochfour seasonal variable weir
b)(i) the design of the new weir and fish pass(es) will allow appropriate attractant flows, water depths and velocities to be passable by salmon at all the appropriate life cycle stages and times of year for each structure based on known attractant flows, swimming capabilities etc.   (ii) the changes in water levels and flows will not increase the number of smolts existing Loch Ness via the Caledonian Canal (in which they are likely to perish), rather than the River Ness. Evidence should be based on transparent and justified realistic worse case scenarios for water levels and flows at, around and   over/through the weir and lock gates, considering the cumulative effects of all Loch Ness water users and the effects of climate change.	To ensure the migration of salmon from the River Moriston SAC is not impeded at Dochfour weir as a result of changes to water levels in Loch Ness from operation of (a) the scheme and (b) the proposed seasonal variable weir
c) how the predicted changes to the flow regime in the River Ness will affect migrating Atlantic salmon at all life cycle stages, based on realistic worse case scenarios. This should include an assessment of effects known to be associated with hydropeaking, including stranding and associated mortality caused by increased predation; habitat alteration and loss caused by the repeated wetting and dewatering of the river bed; physiological stress and reduced growth through forcing fish to repeatedly move to seek shelter; and impeding migration. This assessment could usefully be based on the approach set out in Bakken et al (2023)(ref4), using selected criteria which match the River Ness most closely. The assessment should also specify the proposed ramping rate and demonstrate how this will be managed to avoid adverse effects on migrating salmon (see Alfredsen et al 2022)(ref5).	To ensure downstream and upstream migration of salmon from the River Moriston SAC is not impeded in the River Ness as a result of changes to winter flow regime in the River Ness, in particular the effects known from published evidence to be associated with hydropeaking.
d) the effects of the proposed acoustic barrier on salmon adults and smolts will not extend towards the weir in a manner which discourages or prevents access to the proposed new fish passes.   Alternatively or in addition, the applicant may wish to review in more detail based on evidence from elsewhere whether an acoustic barrier in this location is likely to be effective in delivering the intended benefits and worth including in the proposal.	To ensure the acoustic fish barrier proposed between weir and canal does not impede the migration of salmon from the River Moriston SAC. Noise travels faster though the water column than through air and given that that Loch Ness is a narrow body of water, acoustic deterrents could potentially create a wide, or even full-width barrier across the loch, discouraging or preventing smolts moving down stream Knudsen et al 2005(ref6)), and adults moving upstream over the weir and into the Loch.
e) whether any salmon spawning habitat in the lower reaches of the River Moriston will be adversely affected by the operation of the proposed development and proposed variable weir alongside the other consented and proposed schemes in Loch Ness.	To ensure changes to the water level regime in Loch Ness do not reduce the availability of salmon spawning habitat in the lower reaches of the River Moriston SAC

In addition, we advise that further mitigation and modifications are required to ensure that the following impact pathways do not undermine the conservation objective to restore the population as a viable component of the site and result in adverse effects on the integrity of this SAC:

• Salmon may become trapped during construction and dewatering of the coffer dam at the lower control works
• Increased sedimentation / turbidity (non-toxic) in areas adjacent to the lower control works during construction
• Risk of contamination (toxic) from fuel / chemical leakages / and concrete spills at the lower control works during construction
• Risk of sedimentation and pollution during construction of the proposed variable weir
• Intake flow attracting downstream migrating salmon smolts and/or kelts
• Capture of salmon smolts at the intake during periods of abstraction

The mitigation and modifications required are:

Mitigation The following need to be produced and agreed with the consenting authority in consultation with NatureScot:	Reason
a. CEMP covering construction and dewatering of the coffer dam at the lower control works, containing adequate measures to minimise the risks of fish capture and loss.	To ensure salmon from the River Moriston SAC do not become trapped during construction and dewatering of the coffer dam at the lower control works
b. CEMP and Water Management Plan covering construction of the lower control works, containing adequate measures to minimise the risks of toxic and non-toxic pollution entering Loch Ness	To ensure salmon from the River Moriston SAC are nor harmed by sedimentation or pollution around the lower control works during construction
c. CEMP covering construction of the proposed variable weir, containing adequate measures to minimise the risks of toxic and non-toxic pollution entering the water environment	To ensure salmon from the River Moriston SAC are nor harmed by sedimentation or pollution around the proposed variable weir during construction
d. Condition requiring curtailment of operation of the proposed scheme throughout the duration of the smolt migration period through Loch Ness.   Alternatively, the applicant may wish to consider proposing a physical barrier and demonstrating that velocities towards the intake and outside the barrier will not exceed the lower 95% confidence interval of the mean minimum directional water velocity required to initiate a behavioural response resulting in a direction of orientation change in wild smolts (0.092 m/s) (Kundegorski et. al, 2025(ref7)).	To ensure the intake flow does not attract downstream migrating salmon smolts and/or female kelts from the River Moriston SAC. Evidence suggests that non-physical deterrents, also proposed by the applicant, may be ineffective or less effective in the dark, deep, standing waters present in Loch Ness (Turnberry et al 2005(ref 8), Leander et al 2021(ref9)). Of the mitigation options currently proposed, curtailment is the only one certain to be effective and would therefore be required. Based on currently available information curtailment would need to be in place for the full duration of the period smolts from the River Moriston are migrating through Loch Ness, on a 24 hour basis. The dates could be determined by operating rotary screw traps on the lower River Moriston and the upper River Ness. While smolts are more likely to migrate at night in the early part of their migration, later on they migrate during the day as well.
Modification e. The intake screen mesh size must be reduced to 10mm	To avoid the risk that salmon smolts from the River Moriston SAC will be captured at the intake during periods of abstraction. SEPA guidance (SEPA, 2015(ref10)) states that screen gap sizes >10 mm may be acceptable if the proportion of salmon smolts <11.5cm in length is insignificant, however evidence presented in Ness District Salmon Fishery   Board, 2023(ref11) indicates this is very unlikely to be the case.

In summary, with the information available at present and for the reasons detailed above, we conclude the following conservation objectives for Atlantic salmon are undermined by the proposal:

2a. Restore the population of Atlantic salmon, including range of genetic types, as a viable component of the site

2c. Restore the habitats supporting Atlantic salmon within the site and availability of food

Other potential impacts on Atlantic salmon arising from the proposal

In relation to other pathways by which the proposal could affect Atlantic salmon in the Moriston SAC, the appraisal we carried out considered the following:

• We agree with the conclusion in the shadow HRA that, provided the mitigation measures set out in the shadow HRA Section 6.3.18 and in Chapter 9 Aquatic and Marine Ecology section 9.9.7 are strictly adhered to, salmon migration will not be affected by noise disturbance from heavy machinery, sediment movement, or the temporary cofferdam during construction at the lower control works.
• We agree with the conclusion in the shadow HRA that it is unlikely that smolt (and adult salmon) mortalities will arise from being impinged on the intake screens, as maximum draw velocities are proposed to be limited to escapable velocities for salmon.
• Adult Atlantic salmon will pass by many inflows of various size and discharge as they migrate to their spawning grounds. Returning adults also have a strong, and well recognised, motivation to return to, and ascend, their natal streams rather than alternative outflows and tributaries. Any potential delays in the migration of adult salmon because of attraction to the outfall are therefore not likely to result in population-level impacts.
• The operation of the development will add further localised spatial variations in temperature but will not inhibit the ability of salmon to move within Loch Ness to areas suitable for optimal growth. Changes to the thermal regime in Loch Ness are therefore not likely to affect salmon growth and survival.
• It is unlikely that any reduced productivity of the littoral zone because of changes to the water level regime in Loch Ness will result in population-level impacts on salmon. Whilst some salmon parr may leave the Moriston during autumn to overwinter in Loch Ness, our judgement is that it is unlikely that significant numbers of juvenile Atlantic salmon from the River Moriston SAC utilise Loch Ness as a primary feeding area and, given the naturally limited size of the littoral zone, the importance of this habitat as a feeding area may be low.

1. Freshwater Pearl Mussel

To enable us to carry out our appraisal to inform your appropriate assessment further information is required in relation to the following impact pathway:

• Impacts on the freshwater pearl mussel population as a consequence of impacts to the Atlantic salmon host species

The further information set out above for Atlantic salmon is needed to assess whether the impacts are sufficiently small, or capable of being mitigated, to allow conditions suitable to restore the population as a viable component of the site and to restore the distribution and viability of freshwater pearl mussel host species and their supporting habitats.

References

4. Bakken, T. H., Harby, A., Forseth, T., Ugedal, O., Sauterleute, J. F., Halleraker, J. H., & Alfredsen, K. (2023). Classification of hydropeaking impacts on Atlantic salmon populations in regulated rivers. River Research and Applications, 39(3), 313–325. https://doi.org/10.1002/rra.3917

5. Alfredsen, K., Juárez-Goméz, A., Kenawi, M.S.R., Graf, M.S. & Saha, S.K. (2022). Mitigation of environmental effects of frequent flow ramping scenarios in a regulated river. Frontiers in Environmental Science, 10 -2022. https://doi.org/10.3389/fenvs.2022.944033

6. Knudsen FR, Enger PS, and Sand O. 2005. Avoidance responses to low frequency sound in downstream migrating atlantic salmon smolt, salmo salar. Journal of Fish Biology .45(2):227-233

7. Kundegorski, M.E., Honkanen, H.M., Stephen, A., Torney, C.J., Killen, S. and Adams, C.E., (2025) Defining the water flow cues for navigation in migrating Atlantic salmon smolts. Scottish Centre for Ecology and the Natural Environment, SBOHVM, University of Glasgow, Glasgow, UK. https://doi.org/10.1111/jfb.70004

8. A.W.H.Turnpenny & N. O’Keeffe (2005) Bubble screens in combination with other behavioural stimuli, Screening for Intake and Outfalls: a best practice guide. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/291568/scho0205bioc-e-e.pdf

9. Leander J. Klaminder G. Hellström M. Jonsson M (2021) Bubble barriers to guide downstream migrating Atlantic salmon (Salmo salar): An evaluation using acoustic telemetry. Ecological Engineering 160 (2021) 106141 https://doi.org/10.1016/j.ecoleng.2020.106141

10. SEPA, 2015. Guidance for developers of run-of-river hydropower schemes https://www.sepa.org.uk/media/383805/guidance-_for_developers_of_run_of_river_hydropower_schemes.pdf

11. Ness District Salmon Fishery Board 2023 Annual Report (2023) https://ndsfb.org/wp-content/uploads/filr/5128/NDSFB%20Annual%20report%202023%20Final.pdf

The full objection can be found on the ECU website or you can request a copy from Save Loch Ness