NatureScot assessment of the impacts on River Moriston SAC and North Inverness-shire Lochs SPA – Objection
Thank you for the additional time to allow us to fully assess the impacts on River Moriston SAC and North Inverness-shire Lochs SPA. This response should be read alongside our response dated 11th November 2025 which advised on the implications for Urquhart Bay Woods SAC and Ness Woods SAC.
- 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.
2. 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, the 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.
- 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:
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.
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)( Ref 2) 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) (Ref 3).
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 in this letter 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.