Measuring water velocity under ice in Galena
Nolan Aloysius drills a hole, using an ice auger as the team takes river flow velocity measurements under ice in Galena, on the north bank of the Yukon River.
April 11, 2025
Ben Loeffler and Luke Woodhouse of ACEP’s hydrokinetic team went to Galena, a community of around 500 on the north bank of the Yukon River, in late February to measure how fast water runs under ice.
Very little research has been done and almost no data is available on the speed of the river flow beneath the ice. Field measurements will help the team assess the feasibility of under-ice projects and gauge their current and future projects.
In summer, river flow measurements can be as simple as towing a measuring device behind a motorboat and taking continuous measurements. An ADCP, short for an acoustic Doppler current profiler, is a device that uses sound waves to measure the speed and direction of currents throughout the water column.
Galena residents Tig Strassburg (left) and Nolan Aloysius (center) look over the section of the Yukon River where the team is set to take measurements as ACEP’s Luke Woodhouse (right) prepares the data recording software.
Taking measurements in winter is an entirely different story. After ice-up, the river width has to be divided into a series of equally spaced points for measurements, where holes are drilled in the ice and an ADCP is lowered into the flow.
Two different locations were identified with input from community members as their areas of interest.
With the help of Galena residents Nolan Aloysius and Tig Strassburg, the team took measurements. Pushing a sled with a mounted ADCP along the path, they used a 10-inch ice auger to drill holes in a straight transect — a straight line across the river — at intervals of approximately 25 yards.
Each transect gave the team many challenges, from damaging the auger blades with silt and rock-laden ice to ice accumulating on the ADCP, limiting the depth they could record.
Their measurements ultimately yielded that river velocities were a quarter to a third of those in the summertime. Further investigation revealed dramatically lessened turbidity — the water was clearer — and a potential lack of debris in the river after ice-up.
“We are happy that our preliminary measurements were successful,” said Loeffler. “And the challenges we faced provide valuable feedback for planning future under-ice testing.”
Trying to catch the last light, Luke Woodhouse (left) drops a GoPro mounted with lights in a hole the team drilled in the ice as Nolan Aloysius and Tig Strassburg look on.
In addition to their primary goal of taking river measurements, the team made the best of their stay to learn more about energy efforts in Galena. They sat in on community meetings where the future of energy in the community was discussed and they toured the construction site for the new photovoltaic array.
They even got a bonus of getting out on a cross-country ski on local trails.
Learn more about ACEP’s marine energy research.