HUNTLEY — When the headgates opened on the Bureau of Reclamation’s Huntley Irrigation Project on the Yellowstone River in 1907, the engineering marvel transformed the valley east of Billings from sagebrush rangeland into fields green with alfalfa and other crops. Today, the massive waterworks is at the center of another engineering challenge: helping fish access habitat.

Where the river flows over the project’s concrete diversion dam, it becomes a roaring wave that presents a major obstacle to fish trying to move past it. At a creek-like channel built to allow fish to bypass the structure, a pair of Montana State University graduate students have spent their summer gathering data that could one day help improve it.

On a typical day in July, Haley Tupen, who is earning her master’s in civil engineering in the Norm Asbjornson College of Engineering, and Ian Anderson, a master’s student in ecology in the College of Letters and Science, piloted a jetboat to the diversion site from a few miles downstream. Tupen unpacked her GPS and surveying equipment to map the channel’s streambed, while Anderson downloaded data about which fish had recently visited the bypass.

Montana Fish, Wildlife and Parks invited MSU to conduct the research after lengthening the bypass in 2015 with the idea that it would be easier for fish to navigate, according to FWP fisheries manager Mike Ruggles. This stretch of river hosts a sport fishery complete with sauger, a native relative of walleye, and burbot, an eel-like freshwater cod. Both species have experienced declines, causing concern among wildlife officials.

“We wanted to make sure this bypass is working, and if not, how it could be improved,” Ruggles said. “The hope is we could apply the findings to other areas as well.”

Anderson and Tupen are carrying on an MSU tradition of engineers and ecologists working together to better understand how structures can be designed to help fish overcome obstacles. Most recently, the MSU Fish Passage and Ecohydraulics Research Group studied ways to optimize fish ladders in the Big Hole River watershed that help Arctic grayling swim over irrigation structures and reach cooler waters during the heat of summer.

As a result of ongoing research, “more and more we’re finding that fish move around (in watersheds), and they move more than we expected,” said Alexander Zale, professor in the Department of Ecology and leader of the U.S. Geological Survey’s Montana Cooperative Fishery Research Unit. It’s thought that sauger and burbot are moving extensively up and down the Yellowstone River to spawn, feed and access the best winter and summer habitats, he said.

Past research about fish passage has tended to focus on fish ladders and similar structures and not the bypass channels like the one at the Huntley site, Zale added. “There’s never been an assessment of this kind of bypass before,” he said. “It could be very useful for a lot of other people managing big rivers.”

Starting in March, Anderson, working with technician Evan Matos, a junior at Rocky Mountain College in Billings, as well as FWP staff, captured more than 1,600 sauger, burbot and other fish and fitted each with a small radio transponder. The fish were then released downstream, and radio antennas at the bypass record when the fish pass through different parts of the channel.

“Every day there are multiple detections,” he said. “It’s a ton of data, which is good. It shows that fish are using it to some degree.”

But questions remain about whether certain kinds of fish are more inclined to use the bypass than others, and during what times of the year, he said. During spring runoff, the bypass was a roaring torrent; during July it was a shallow riffle.

That’s where Tupen, the engineer, comes in. In addition to creating a detailed map of the channel, she measured the flow levels in the bypass throughout the summer. Back in the lab, she will combine the data to generate models of the channel’s streamflow. From other research, the team knows the approximate swimming ability of the fish and can then determine, for instance, whether the flows are too high for the fish to navigate during a certain time of year. Those findings can be compared to Anderson’s observations of actual fish.

“This modeling project is on a bigger scale than what we’ve done before, so it’s a good challenge for us,” said Katey Plymesser, a leader on the project and assistant professor in the Department of Civil Engineering. “I continue to be excited by these collaborations between ecology and engineering students.”

Eventually, Plymesser said, the findings could be used to modify the bypass channel to tailor its effectiveness for certain fish or to engineer additional forms of fish passage.

Tupen and Anderson will continue with the field work through next summer. “This has been a great opportunity to learn,” Anderson said. “And who doesn’t want to work on the Yellowstone?”