Glen Franka Reservoir is an impounding reservoir on the Leadhills Estate. An impounding reservoir consists of a dam across a valley which acts to impound a natural stream of water. The exact date of completion is not clear but is thought to be around the mid-1860s (see description of works) following commissioning by the then Leadhills Mining Company “in connection with the Leadhills Mines and Works” – presumably to act as a body of water for all manner of functions including flushing, cleaning and processing the mining operation. Today the reservoir is mainly used for fishing and recreational use.

Overflow from the Glen Franka Reservoir is by a gravity spillweir and channel located at the north east end of the dam. Water discharges down a channel running past a small downstream reservoir and discharging into the Shortcleugh burn further downstream. Additionally, there is a 400mm discharge pipe lying at a depth of 8.5m, with a downstream valve that when open provides a flow of water to the Leadhills village.

It is formed by an earth embankment dam across the Shortcleugh Water in a fairly deep sided valley. The embankment dam is approximately 110m in length with a maximum height of approximately 11m. The reservoir surface area is in the region of 48,000 square meters or 11.8 acres, has a maximum impounded depth of 9m and a capacity of 154,000 m³. Topographical survey data shows that below 5m, there is only 10% of the total volume of the reservoir.

Following a re-categorisation of the dam by SEPA from Category C to category B, there is a resulting deficiency in its ability to pass flood event legislation, namely a 1 in 10,000 year flood event! This will require a widening and/or deepening of the spillweir as well as additional measures such as a syphon to more rapidly lower water levels in the event of a flood event. Additionally, a conditional survey was required to assess the integrity of the discharge pipe and more importantly whether an upstream valve could be fitted. Leadhills Estate has commissioned a number of surveys and investigations into these issues and the work is ongoing.

An important condition of the resulting works will be the need to future proof the reservoir in terms of safety and statutory compliance for an additional 150 years and maintain its increasing importance as a fishing and recreational feature for the community of Leadhills.