New reservoir at Haukeli secured with fiber optic monitoring

Statkraft's new water reservoir at Haukeli is a pilot for new technology. More than two kilometres of fibre optic cables provide a safety net - extra security and possible new answers," says project manager Arne Sandvold at Statkraft.

Kjela Dams on Haukelifjell in Vinje municipality have been completed one year ahead of schedule. Arne Sandvold led the work. It started in September 2022. Cautus Geo delivered new technology to Statkraft's pilot project for automatic and continuous monitoring of deformation and leakage.

- We are well accustomed to instrumented monitoring. Manual control routines and technology are often used in close interaction. Here, we've also built in a lot of fibre cables that provide extra security, both through automatic and continuous monitoring and possible new knowledge," says Sandvold.

400 million

The new Kjela Dam is a major construction project. The total cost is over NOK 400 million in 2022. The plant was handed over from the contractor to Statkraft in December last year.

The main dam is 250 metres long and 34 metres high. In addition, the barrier dam is 340 metres long and 24 metres high.

- We have control over possible leaks. It is collected and measured per second. At Kjela-Dammer, 3D and fibre cables are added. This provides extra security. If a leak occurs, we can pinpoint the exact location, not just reveal whether it's on the left or right side of the dam," says Sandvold.

Control regime

Dam systems are monitored and controlled according to set rules. They also involve manual checks using traditional surveying technology.

- Here we have technology we have not previously used on dams in Norway. The pilot project will also be able to show whether technology can be used to change control systems and routines. It's an exciting project where the answers will come over time," says Sandvold.

- Everything is fully installed. The work was carried out in parallel and integrated with the dam construction. Most of it was put in place during the autumn of last year with a combination of fibre and SAA inclinometers," says CTO Lars Krangnes of Cautus Geo.

temperature

- The key to uncovering specific leakage points is temperature, which is measured every metre along the cable. Fibre cables can be heated. The speed of the temperature drop is then affected by humidity and leakage points can be identified with great accuracy," says Krangnes.

Kjela-Dammer is also instrumented for ongoing, automatic and continuous monitoring of settlements.

- Inclinometers in the core of each dam are technology Cautus Geo has used in several power dams both in Norway and abroad. "What's new in this project is the use of fibre technology for monitoring leakage and deformation," says Krangnes.

Different levels

For leakage measurement, fibre cables have been installed at different levels in the ponds. They measure temperature with high accuracy at intervals of one metre. The theory is that moist areas will have a different temperature than where there is no water. In addition, the cables can be heated at specific time intervals. Areas with a faster temperature drop give a better indication of water ingress.

- The most advanced and novel method at Kjela is a 3D fibre cable that was established in the crown of each dam. This is buried in the top of the dam and measures 3D deformation along the cable, which consists of four individual fibre cables. "We're talking about a new technology that is rarely used and has great potential for effective monitoring of large structures," says Krangnes.

Instrumentation

Two inclinometers. Measurement of deformation with 0.5 metre resolution.

• 1 pc. SAAV of 27 metres.
• 1 pc. SAAV of 32 metres.

Fibre cables for leak detection (temperature measurement).

• Main dam - 3 heights, totalling 1072 metres.
• Sperredam - 2 heights, totalling 1069 metres. The cables can be given high heat to reveal any leakage points.

3D fibre cable for deformation measurements at the top of the dam. 

• Main dam - top dam - 235 metres.
• Sperredam - top dam - 324 metres.