Hydro

Hydro

The Ness catchment has been heavily exploited for its energy potential, primarily hydro, although in recent years many wind farms have appeared on the skyline. One of the earliest large-scale hydro schemes in Scotland was developed at Foyers in the late 1800s. This scheme was built by, the then British Aluminium Company, to power a smelter on the shores of Loch Ness. Although the smelter is long closed, this hydro scheme still operates, in conjunction with the Foyers pump storage hydro, operated by SSE.

In the 1940s the two big storage hydro schemes in the Ness catchment were developed, harnessing the power of the Rivers Garry and Moriston. The Garry scheme had a massive impact on the Garry salmon population with the badly conceived heck, fish traps and hatchery, preventing access to over 30km of what were the salmon spawning headwaters of the Garry system. In the early days of trap operation over 800 adult salmon were trapped at the Poulary Heck but this soon diminished and by the early 2000s virtually no salmon were returning to the heck. The fish trap and hatchery operation were designed to replace the lost spawning in the Loch Quoich tributaries, but access the River Kingie was also prevented.

The situation in the Moriston is less clear as it seems that the salmon population in the Moriston is a recent one. The falls at just above Loch Ness were eased in the late 1800s/early 1900s with fish passes improving access into the upper reaches. It seems unlikely, however, that the upper Moriston was completely devoid of salmon though. The Moriston also supports a large freshwater pearl mussel population, which in this case, use salmon as a co-host for the larval stage, and an etching from 1778 depicts large numbers of salmon leaping at the waterfall.

At one time the River Garry was the best spring fishery in Scotland and was famed for its early running, and large salmon. In more recent decades other causes contributed to the decline; the coming of loch cage salmon smolt aquaculture for example, with regular escapes of farm origin fish, and even deliberate stocking of farmed salmon parr by the Ness DSFB. What seemed like the terminal decline of the upper Garry salmon population led to the formation of the Upper Garry Salmon Restoration Project in 2014, although the project have been germinating for a few years prior. This partnership, which is largely funded by SSE, includes Ness DSFB, Ness & Beauly Fisheries Trust, Mowi, University of the Highlands and Islands, SEPA and Garry Fishings. This has been a successful and resilient partnership, and in 2023 the millionth salmon egg was stocked in the upper Garry. Whether this results in increased numbers of returning adults remains to be seen, although there have been some encouraging signs.

As well as blocking fish passage hydro dams can prevent the movement of sediment, which salmon need for spawning. Sediment starvation downstream of dams is now recognised as a major impact on river, and salmon ecology, as is flow regulation. In some cases, salmon do well in regulated rivers, by the loss of river dynamics usually limits natural processes.

In recent years we have been working closely with SSE, and other Ness hydro operators to try and mitigate these impacts. For example, the onset of freshets on the Moriston was moved forward from the start of May to the beginning of April, to assist smolt migration. We are also working with SEPA and SSE to introduce flow variability into the upper Moriston, in a part of the river where the compensation flow is the same every day of the year. Gravel reintroduction is another priority on both the Garry & Moriston.

In the last two decades many of the smaller tributaries have “run-of-river” hydro schemes. This type of scheme doesn’t involve water storage, so they can only generate when flows are above minimum. In most cases these schemes are upstream of impassable waterfalls and are therefore less significant for salmon. They can alter sediment passage though.

Much work remains to be done to mitigate the impacts of hydro on the Ness salmon population.