Aquatic Control Engineering

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Fish Pass @ Loch Duntelchaig

Loch Duntelchaig forms a major tourist attraction in the Inverness area and is renowned for its fishing. To enable fish stock to be maintained at a healthy level, the loch utilised a traditional V Notch fish pass.

Like most fish passes the V notch fish pass is dependent on water level with little variation. At many locations this will only cause a problem in either extreme events, but what if dramatic level changes are a certainty?

This was the problem confronted at Loch Duntelchaig where variations in water level can reduced the fish passes performance. The solution came from technology more commonly used in water level control.

To allow the pass to move technology was repurposed from the water flow control industry, in particular replacing fixed concrete walls with tilting weirs that can be adjusted with the water level. The tilting weirs used in the fish pass at Loch Duntelchaig where custom built to include a V notch with adherent nappe to provide fish passage. Control over the tilting weirs came from another piece of technology found in the water flow control industry. The “Greenbox” is a standalone unit, designed to sense water levels and adjust equipment such as a tilting weir to a suitable position. In the case of the fish pass at Loch Duntelchaig, this meant keeping the upper and lower water levels within the boundaries to allow fish passage.