Improving water flows in the River Cour


River Cour featured

Since 2009, when the first River Basin Management Plans were published, SEPA has been working with key stakeholders and partner organisations to improve the classification of rivers and other water bodies that were highlighted. Here we look at just one of the success stories, the The Allt Coire Eoin (River Cour) on the West Coast of Scotland.

A significant number of Scotland’s rivers and lochs are used to provide water for hydroelectricity generation. This includes a growing number of small, run-of-river schemes along with much larger, mainly long-established, schemes that make use of water stored in large reservoirs.

Storage hydro schemes play a vital role in generating renewable energy but in some cases they can lead to water bodies being substantially altered. As a result of this, many of the rivers and lochs affected were designated as ‘Heavily Modified Water Bodies’ in the first River Basin Management Plans (RBMP) which were published in 2009.

The Allt Coire Eoin (River Cour), which has been classed as a ‘Heavily Modified Water Body’, has been one such example of a waterbody which has been altered by the operation of a hydro scheme, specifically by the operation of an impoundment structure for the purposes of the abstraction of water.

The starting point

The Cour is a fast-flowing spate river that flows into the River Spean, which in turn joins the River Lochy – one of the most important salmon fisheries on the West Coast of Scotland.

The water body formed part of the larger Lochaber hydro power scheme, operated by Rio Tinto, which, from the date of construction in the 1920s, prevented continuous flows being released into the downstream river.

The River Cour (downstream of the main intake) prior to the improvements being made.

The River Cour (downstream of the main intake) prior to the improvements being made.

The scheme diverts, stores and abstracts water from a number of catchments starting at the upper end of the River Spey and moving west to include parts of the River Spean and surrounding tributaries. Due to the resulting significant ecological impacts, including impacts on fish migration and habitat, the River Cour was classed as having ‘Poor Ecological Potential.’

The section of the River Cour impacted by reduced flows was within the accessible limit of migratory salmonids and, following investigatory survey work, it was confirmed that there were areas of the river which would provide good juvenile fish habitat if there were suitable water flows. It was also recognised that a significant length of the waterbody would benefit from having environmental improvements.

As a result of this, the first RBMP included an objective to improve the ecological quality of the River Cour with the aim of ensuring it could achieve ‘Good Ecological Potential’ by 31 December 2015.

SEPA has since worked with Rio Tinto and other key stakeholders to achieve this objective.

How was it improved?

Ensuring an appropriate balance between the requirements of the RBMP with the need for renewable energy generation, a proposal was developed that would restore a continuous low flow of water to six kilometres of the River Cour.

The new release of water was to be provided at Rio Tinto’s main River Cour water intake via a new three metre orifice cored through the concrete dam wall. This was designed to facilitate a minimum continuous flow of 75 litres per second and maintain the ecology of the river.

The main intake after improvements were carried out.

The main intake after improvements were carried out.

The design, which had been audited by SEPA, also ensured that the new environmental mitigation flow will be delivered before the abstracted flow of water is removed at the intake.

The required engineering modifications to the intake have now been completed and the new flow mitigation is now being delivered.

This work has improved the ecological quality of the river by providing flow conditions that enhance aquatic biodiversity. This section of the river has become accessible to migratory salmon, and the quality of the river habitat is now suitable for juvenile salmonids.

To reflect these improvements, SEPA’s classification of the River Cour has gone from ‘Poor’ to ‘Good Ecological Potential.’

The River Cour after the improvements were carried out.

The River Cour after the improvements were carried out.

What next?

During subsequent RBMP cycles SEPA will continue to improve water bodies affected by Scotland’s older hydroelectricity generating schemes according to a balance between where we expect the greatest environmental benefits for the least potential loss in generation.

To ensure our goals for the water environment do not significantly impact on the important economic benefits which hydropower brings, we are committed to limiting the reduction in electricity production resulting from the improvements (made between 2009 and 2027) to 100 gigawatt hours per year. This represents around 2% of the hydroelectricity generated in Scotland in 2010.

The criteria for prioritising future water bodies, impacted by hydroelectricity generation, for action will include the following:-

  • SEPA’s latest information on where there are significant ecological impacts, including disruption of fish migration;
  • The area of the water environment expected to benefit from environmental improvements.
  • The potential loss of generation to deliver the appropriate flows.

This approach will ensure that we do not compromise progress towards the achievement of Scotland’s target for the equivalent of 100% of our electricity demand to be supplied from renewable sources by 2020.

The Water Framework Directive was implemented in Scotland through The Water Environment and Water Services (Scotland) Act 2003 and The Water Environment (Controlled Activities) (Scotland) Regulations 2011.

This regulation requires SEPA to lead and co-ordinate river basin planning in Scotland’s river basin districts to protect and improve Scotland’s water environment with a planned programme of measures set out in the River Basin Management Plans (RBMP).

The purpose of the Water Framework Directive is to establish a framework for the protection of inland surface waters, estuaries, coastal waters and groundwater. The framework for delivering the Directive is through River Basin Management Planning.

Scotland has been split into two River Basin Districts (Scotland and Solway Tweed). Each River Basin District has been characterised into smaller management units known as water bodies. The surface water bodies may be rivers, lochs, estuary or coastal.

Heavily Modified Water Bodies (HMWBs) are water bodies which, as a result of physical alterations by human activity, are substantially changed in character and cannot therefore meet ‘Good Ecological Status.’

The ecological quality of HMWBs is described by their ‘ecological potential.’ This is a measure of how the ecological quality of such a water body compares with the maximum quality achievable without significant adverse impacts on:

  • The purposes served by the physical alterations (e.g. storage hydropower generation); and
  • The wider environment.

The ecological quality of a HMWB is described by its ecological potential. The ecological potential of a HMWB may be maximum, good, moderate, poor or bad.

We identify whether a HMWB meets its ecological potential or not by:

  • Identifying the impacts affecting the water body;
  • Identifying whether or not all practicable improvements have been made to the physical characteristics of HMWBs;
  • Assessing whether those improvements have been under taken.

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