In the race to achieve net zero, the demand for innovative renewable energy solutions has never been greater. Scottish Water Horizons is leading the charge with Europe’s first siphon-fed hydro power project at Whiteadder Reservoir in East Lothian.
This 199kW hydroelectric scheme harnesses the natural flow of water to generate clean electricity while enhancing reservoir compliance. Unlike traditional hydropower systems, the siphon-fed design eliminates the need for major infrastructure changes, providing a cost-effective, low-impact energy solution that could set a precedent for future hydro projects across the UK.
Electricity generated by the scheme is used to power the nearby Hungry Snout Pumping Station, a vital asset in East Lothian’s water network, which pumps up to 32 million litres per day to Castle Moffat Water Treatment Works. By offsetting grid electricity demand, the project reduces operational costs, cuts carbon emissions, and supports Scottish Water’s ambitious net zero targets by 2040.
From concept to reality
The idea for the Whiteadder Reservoir hydro project was developed through a combination of data-driven analysis and local operational expertise. By assessing flow and pressure data, reservoir compliance reports, GIS mapping, and on-the-ground insights, Scottish Water Horizons identified an opportunity to generate renewable energy from a previously untapped resource.
A feasibility study confirmed that the reservoir’s 24m head height and seasonal flow variations (150 – 1200 l/sec) provided ideal conditions for a hydroelectric system. However, securing a grid connection proved to be a key challenge. The project was originally designed as a 214kW scheme, but local grid constraints required a redesign to 199kW. While this adaptation reduced generation capacity slightly, it significantly lowered grid connection costs which speeded up project delivery.
Stuart Clark, Development Project Manager with Scottish Water Horizons, explains: “The grid connection challenge forced us to rethink our approach. At first it seemed like a setback, but in the end, it helped us refine the project to make it more commercially viable. By slightly reducing the turbine size, we were able to accelerate the project timeline while maintaining strong energy generation potential.”
The siphon-fed hydro system
At its core is a 199kW Ossberger Crossflow turbine, housed in a powerhouse at the base of the dam. Water is drawn through a submerged intake, lifted over the dam via the siphon system, and then directed through the turbine – generating clean electricity before flowing into the Hungry Snout Pumping Station.
Beyond energy generation, the siphon system enhances reservoir compliance by increasing drawdown capacity – a critical requirement under SEPA (Scottish Environment Protection Agency) regulations. This eliminates the need for a separate multi-million-pound infrastructure project, making it a cost-effective solution.
Clark adds: “This is a completely new way of implementing hydropower on an operational reservoir. Traditionally, increasing reservoir drawdown capacity would require a separate capital project, often costing millions. By integrating smart controls with the siphon system, we’ve created a solution that not only ensures compliance with reservoir regulations but also maximises renewable energy generation.”
A sustainable solution
Beyond financial savings, the scheme will also deliver substantial environmental benefits. The hydro turbine is expected to generate 820,000 kWh of renewable electricity per year, offsetting 30% of the Hungry Snout Pumping Station’s energy demand and reducing carbon emissions by 111 tonnes of CO2 annually.
Alan Mearns, Delivery Project Manager with Scottish Water Horizons, says: “This project is about much more than just generating renewable electricity. It’s about delivering a solution that makes economic sense, enhances infrastructure resilience, and supports long-term sustainability goals. By optimising how we use our existing assets, we’re not only reducing costs but also making a significant progress towards Scottish Water’s commitment to net zero.”
Construction & commissioning
Construction at Whiteadder Reservoir began in August 2023, starting with site access, temporary tracks, and key infrastructure installation.
A major engineering challenge was laying the penstock pipeline up the dam face, requiring precise excavation and installation on steep terrain. A specialist diver team was brought in to carry out the work under carefully controlled conditions, ensuring safe installation of the submerged intake without impacting water quality.
With the pipeline in place, the Ossberger Crossflow turbine was delivered and installed by Emtec Energy, working in partnership with Dulas and Ossberger GmbH. Commissioning followed a rigorous process, including pipework pressure testing, valve function checks, and both electrical and mechanical commissioning of the turbine system. The project also underwent grid accreditation (G99 compliance) and a 14-day reliability testing period, ensuring seamless integration into Scottish Water’s infrastructure.
Following successful commissioning, the system was transferred to Scottish Water for long-term operation and maintenance.
“From concept to completion in just over three years, this project demonstrates how complex hydro schemes can be delivered at pace,” Mearns reflects on the project’s success. “What’s even more exciting is that it’s a replicable model – one that could unlock further hydropower opportunities across Scotland.”
Shaping the future of renewable energy
The Whiteadder Reservoir hydro project marks a major milestone for Scottish Water, proving that siphon-fed hydro systems can be successfully integrated into an operational reservoir without disrupting the public water supply. Now fully operational, the scheme is set to deliver long-term benefits including reduced energy costs, lower carbon emissions and enhanced infrastructure resilience.
Building on this success, Scottish Water Horizons is already exploring other hydropower opportunities across its asset base, using Whiteadder as a model for future projects.
As Clark sums up: “We are constantly looking for ways to use our assets to generate renewable energy. The Whiteadder project is just the beginning – we are fully committed to developing innovative solutions that contribute to Scottish Water’s and Scotland’s sustainability goals.”
By combining smart technology with innovative engineering, Scottish Water Horizons has demonstrated a scalable and cost-effective approach to integrating hydropower into critical infrastructure. As the UK accelerates toward net-zero, projects like this highlight the untapped potential of existing assets – proving that even long-established infrastructure can be reimagined for a greener future.
