Contract on behalf of Marine Harvest

Assessment of the capacity of Garry to accommodate additional inputs of phosphorus without compromising the current WFD/ RAG status

Aim The purpose of this report is to provide an evaluation of the capacity of Loch Garry to accommodate increased contributions of phosphorus without adversely affecting the current WFD (Water Framework Directive) and Red Amber Green RAG) water quality status. This has been done using the PLUS+ model in its standard configuration as used by SEPA. This model uses the LCS88 land cover and 2001 population census data as input parameters.

PLUS+ model The James Hutton Institute’s predecessor, the Macaulay Land Use Research Institute, developed the Phosphorus Land Use and Slope (PLUS) model in the 1990’s in association with the Forth River Purification Board (formerly a regional office of SEPA); with financial support from Scottish Natural Heritage. The PLUS model was developed to determine the relationship between anthropogenic drivers of nutrient enrichment (especially Phosphorus [P]) and trophic status of standing waters in . The model was applied to 170 lochs and proved to be a robust tool.

SEPA were very interested in using PLUS to undertake further assessment of loch phosphorus concentrations/ loads in response to changes in land cover and point sources of P. However, the PLUS model was based on old GIS technology, lacked any kind of user friendly interface, and had no facilities for maintaining records of simulations in a central database. In collaboration with SEPA, significant progress has been made towards addressing these issues and following 8 years of development, refinement and testing, PLUS+ is now recognised as a credible management tool for assessing new fish farm license applications. The most recent development with PLUS+ has been to update the land cover data used to derive the phosphorus loads, however since these new data are not currently part of the PLUS+ configuration used by SEPA the landcover from the LCS88 were adopted in this study.

PLUS+ sums the various sources of P in the model to calculate phosphorus concentration (TP – Total Phosphorus in micrograms per litre – µg / l) and calculated phosphorus loads (J in kg). SEPA provides measurements of P in µg/ l and PLUS+ calculates the equivalent load in kg. Where the load is known the concentration can be calculated and vice versa using the area and mean depth of the loch.

A comprehensive description of the model, data sources and calculation methods can be found in the user manual which can be downloaded here.

Loch Garry catchment description Loch Garry (NH 22491 01951) is 11 km long, has maximum depth of 64.9 m and is situated 25 km north of Fort William, (Figure 1).

Figure 1: Location map. The total catchment area of Loch Garry is 164 km2. Water flows from Loch Quoich 10 km upstream to the west), down to Loch Poulary and then enters Loch Garry at its western point at Inchlaggan. Loch Garry is part of the Garry-Moriston Hydro- Electric Scheme (Figure 2). The east end of the loch is dammed, after which the River Garry flows into Loch Oich and then . There is also a system of locks that complicate the hydrological transfer of P to and from Loch Oich and . No account has been taken of this transfer in the current model application. There is no movement of water from the scheme at Glenmoriston into the Garry Catchment.

Figure 2: Garry-Moriston Hydro-Electric Scheme ( Wood, 2005)

Power generation results in artificial fluctuations in water levels which can be quite pronounced, thus affecting the capacity of the loch and retention times for nutrient processing. The capacity and retention times of the loch are parameters in PLUS+, however, artificial changes in the loch water level are not considered in this application. The dam on Loch Garry releases water on one day a week from April to October. The catchment is located in one of the wettest areas in the UK, with over 3,100 mm of rainfall per annum (more than four times that of the east coast of Scotland). The main activities in the Loch Garry catchment are deerstalking (sporting estates) and commercial forestry at low altitudes, and some tourism (mainly hillwalkers). Sport angling takes place both from the shore and from boats during the summer months. Marine Harvest operates a salmon smolt rearing installation near Laddie Wood. Three small cages to the east of the loch were observed on Googlemap. These farms will contribute a quantity of phosphorus to the loch which has not been made available at this time. Sources of phosphorus from sewage effluent are negligible as there are few inhabitants in the catchment .

The catchment is designated as a Site of Special Scientific Interest (SSSI) and is coincident with that of West -shire Lochs Special Protection Area (SPA) for blackthroated divers and the common scoter. The status of this site as a SPA means that there is an obligation on Government to avoid deterioration in the status of the birds and their associated habitat as well as to avoid disturbance of the species for which the area has been designated ( SNH 2007). However, in terms of the water resources, Loch Garry has good ecological potential because the pattern and timing of water abstraction is controlled and an appropriate baseline flow is provided ( North Area Management Plan 2010).

SEPA classified Loch Garry as having an “ overall status of Good ecological potential with Medium confidence in the classification) in 2008 with overall ecological status of Poor and overall chemical status of Pass” ( SEPA, 2009). The SEPA report shows Total Phosphorus status to be High with a high level of confidence on that class.

It is important to note that the five classification ecological potential classes for Heavily Modified Water Bodies (HMWBs) and Artificial Water Bodies (AWBs) combine the level of mitigation measures for water levels and flow and physical habitat with measurements of the biological and chemical water quality. For example, a HMWB could have all the mitigation measures in place for the use (eg hydropower) to allow it to reach good ecological potential, but if water quality is poor due to elevated phosphorus levels, its overall ecological potential assessment could be moderate, poor or bad depending on the severity of the impact ” SEPA 2009). Results

Background phosphorus concentrations

This report is based on SEPA’ s observed Total P data 2014, although data were also supplied for 2009. A small increase in the measured Total P concentration was observed in Loch Garry between 2009 and 2014 (5.4 µg/ l (5,697.2 kg)) and 5.6 µg/ l 5,931.8 kg) respectively). This small (but significant) increase resulted in deterioration in the water quality status reported by SEPA from ‘High’ to ‘Good’. However, the threshold between ‘ High’ and ‘Good’ status for Loch Garry is 5.0 µg/ l and the reason for this reported change in status is not clear as a numerical comparison between the reported concentrations and the High/ Good threshold shows that the status was ‘Good’ in both 2009 and 2014. Observations of TP from other studies at Loch Garry have shown that analytical/ statistical methods used in the analysis of TP can have a significant influence on the concentration reported. For example, Cromey et al. (2010) reported a TP concentration of 5.6µg/ l based on a geometric mean from 2004-2006; Struthers et al.,2016 reported a geometric mean 5.48 µg/ l and arithmetic mean 5.62µg/ l from data collected during May2015-March 2016.The statistical method therefore has clear implications for the water quality status.The report is based on SEPA observations made in 2014.Output from

the PLUS+model The next section of the report is split into 2 parts. a.A standard PLUS+ application to the Loch Garry catchment b.Standard PLUS+ application to the Loch Garry catchment showing the implications of additional TP from the proposed fish farm on the WFD status of Loch Garry and downstream standing waters in the wider Ness catchment. Part (a)

Results are displayed as a concentration in µg/l followed by the phosphorus load either associated with it or derived from it in brackets. Water quality standard High, Good, Moderate, Poor Bad) is described, followed by the Red, Amber, Green proximity to degrading status in brackets, e.g. Good (green). As previously explained all results are derived from the PLUS+ model with the standard configuration as used by SEPA.

There is a clear discrepancy between observed TP 5.6 µg/ l (5,931.8 kg), representing Good (green) WFD status) and modelled TP 4.03 g/ l (3,983.6 kg), representing High (amber) WFD status) in Loch Garry, raising concerns about the suitability of the data used to run the model. Possible explanations for the under prediction of TP in the model compared to the SEPA 2014 reported concentration include: i. Recent changes in the land cover that are not represented in the standard PLUS+ setup. Whilst the distribution of land cover types has changed since 1988, the total export of P to Loch Garry is remarkably similar when both land cover maps are compared LCS88: 2,211 kg P, 2015: 2,205 kg P). However, processes responsible for the timing/ transport of P to the loch are different following land cover change which could party explain the difference between the modelled and observed concentrations of P in the loch. Key land cover changes include recent forest expansion since 1988 (3,074 Ha in 1988 to 3,436 Ha in 2015) resulting in a greater export of P from fertilization; and more significantly, a large area of the catchment being ripped scarified) for new planting in 2015 (potentially causing a disturbance of a large source of P from the soil 416 kg); other recent (post 1988) land use changes include an expansion, possibly into the montane heath, of coarse grassland which has a higher P export coefficient, than montane heath (Table 1). Note: various levels of uncertainty are associated with data derived from spatial information (mapping/ classification). ii. TP inputs from other commercial activities such as the existing fish farm were not included in this calculation. Table 1: Comparison of land cover and associated Total P loads derived from export coefficients from 1988 to 2015

Standard PLUS+ Updated PLUS+ LCS88) 2015) Land Cover Area (Ha) P (kg) Area (Ha) P (kg) blanket bog & peatland 872 23 835 23 Bracken 32 2 30 2 broadleaved woodland 310 61 246 47 coarse grassland 56 6 2609 236 coniferous plantation 3074 430 3436 481 factories & urban 4 7 13 26 heather all types 7712 715 5075 476 improved grassland 126 54 94 37 mixed woodland 7 1 958 172 montane vegetation 946 49 624 35 open canopy young plantation 1787 303 323 55 recently ploughed land 597 445 117 87 Ripping 0 0 1167 416 road & rail 0 0 47 0 smooth grassland 133 11 86 7 Water 781 103 777 105 16437 2211 16437 2205

To assess the effect of additional P from the proposed fish farm on the WFD status, it was necessary to first model the addition of 1,948.2 kg of P to Loch Garry to equal the load computed from the measured concentration ( 5,931.5 kg) and thereby create an appropriate baseline for this assessment ( Table 2). This changes the modelled status from ‘High’ to ‘Good’, matching the SEPA measured status.

From this baseline (equating to the 2014 SEPA measured status), to downgrade the status of Loch Garry to a lower class would require a supplementary input of P of 3,273 kg before the status deteriorates from ‘Good’ to ‘Moderate’ status. Table 2: Loch Garry- Measured and modelled TP and downgrade potential in 2014 High/ Inferre Good High/ Good/ Good/ Mod/ Measured d TP Measured Modelled TP Modelled TP Good Moderate Moderate Poor TP Mod/ Poor TP ( µg/ l) kg) Status µg/ l) load ( J) Status µg/ l) J) TP ( µg/ l) J) µg/ l) J)

Standard PLUS+

5.6 5931. 8 Good 4.03 3983. 6 High 5 5188. 8 8 9204. 3 16 21433. 9

Add 1948. 2 kg to match observed load ( new baseline)

5.6 5931. 8 Good 5.58 5931. 8 Good 5 5188. 8 8 9204. 3 16 21433. 9 Part ( b)

Loch Garry is part of the larger Ness catchment that has an extensive network of 2. 184 sub-catchments which drain an area of approximately 1,800 km 180 of these sub-catchments flow directly or indirectly into Loch Ness. Loch Garry flows into Loch Oich which flows into Loch Ness which then flows into Abban Water and then into Loch Dochfour, therefore phosphorus from any fish farm in Loch Garry will have implications on P concentrations in the downstream network of lochs.

The PLUS+ model is designed for evaluating scenarios. However, in order to evaluate the capacity of Loch Garry to accommodate an additional P load the PLUS+ model must be fully aligned with all of the the relevant available SEPA measured concentrations, in this case for Loch Garry, Loch Oich and Loch Ness. The procedure followed is described in detail in our Loch Ness report. Following the alignment of the PLUS+ model with SEPA’s measured concentrations for Garry, Oich and Ness the maximum P load that could be added to Loch Garry without compromising the existing water quality class of the loch, and those lochs downstream, was calculated to be 1,750 kg. Following this addition, the remaining capacity to downgrade water quality to a lower class in Loch Garry and the other downstream lochs in the system is shown in Table 3.

Table 3: Scenario for inputs Remaining Additional P downgrade capacity load ( kg) kg) Change Loch Garry 1,750 1,522 P addition cascades to downstream lochs impact on Loch Ness 963 796 impact on Loch Oich 1142 47 impact

on Abban Water 351 14, 259 impact on Loch Dochfour 333 892 It is important to recognize that proportion of any P being added to Garry will have an impact on Lochs Oich and Ness and as such they must be treated as a system. In this system of lochs,Loch Oich has the smallest capacity to accommodate additional P from the proposed fish farm in Loch Garry and acts as a principle constraint on the capacity of Loch Garry. A maximum of 1, 750 kg may be added to Loch Garry without changing the status of Loch greater than 1,750 kg would result in Loch Oich’s status being downgraded in the quality and RAG status from its baseline of High (amber) class to Good (green) water quality status.

Disclaimer The PLUS+ model uses mapped landcover and estimated P export coefficients that are subject to unknown levels of uncertainty, and whilst best efforts have been employed to produce a robust report, James Hutton Limited cannot be held responsible for any financial losses or other impacts incurred by Marine Harvest as a result of decisions made based on information contained in this report.

References

Cromey, C.J., Rodger, A.N.S., Treasurer, J.W., 2010. Validation Of OECD-Model For Predicted Impact Of Freshwater Cage Production On In-Loch Total Phosphorus Concentration. ISBN: 978-1907266-36-2.

North Highland Area Management Plan 2010 Catchment Summaries https:// www.sepa.org.uk/ media/ 75596/ doc-23- nh_catchment_summaries_ness.pdf

Scottish Natural Heritage 2007. West Inverness-shire lochs. Site of Special Scientific Interest. Site management statement, Site code: 9189

SEPA, 2009. RBMP Water body information sheet for water body 100190 in North Highland. Loch Garry, SEPA report http:// apps.sepa.org.uk/ rbmp/ pdf/ 100190. pdf

Struthers, W., and Telfer, T. 2016. Water quality in Loch Garry, May 2015 to March 2016. Water Quality report, University of Stirling. WQ 2015-16 F017

Wood, E. 2005. Power from the Glens. The Hydro Boys. Scottish Hydro Electric. Luath Press ISBN 1-84282- 047-8.