North Canal Dam Fish Ladder

North Canal Dam from Google Earth.

North Canal Dam, located just upstream from the Mt. Washington bridge in Bend, is the northernmost irrigation diversion dam on the Deschutes River. Built in 1912 and 33 feet high, it is the largest and oldest dam in Bend. A fish ladder was required to be installed in 2017, providing upstream fish passage for the first time in over 100 years. The dam is on the left in the image above, two major irrigation canals are on the right, and the fish ladder is in the middle, indicated by the red arrow.

The ladder is the longest made of stainless steel in Oregon and was a bit of an experiment. To ascertain its effectiveness, the Oregon Department of Fish & Wildlife conducted a small study from 2018 through 2020 to track passage. 440 redband and brown trout were captured below the dam down to Tumalo State Park and fitted with radio tags. Antennas were placed at the bottom and top of the fish ladder to detect these fish.

The fish ladder. Photo: ODFW.

The study used a small sample and only 12% of the tagged fish entered the fish ladder, but 83% of the redbands and 50% of the brown trout that started passage were later detected at the top. So, at least 52 trout moved upstream over the study period. Additional non-tagged fish most likely used the ladder as well. Given the severely degraded conditions in the river below the dam, it is not surprising that the average fish that made it through the ladder was small: 6 inches for redbands and 8 inches for browns.

All detections occurred during irrigation season, when flows below the dam are low and river temperatures increase. The speculation is that the fish were looking for better habitat.

It is assumed that downstream movement has been occurring since the dam was installed with fish going over the dam in high water in the winter when there is enough flow allow them to survive the plunge. The dam that creates Mirror Pond adjacent to the Newport Avenue bridge is the last remaining dam on the Deschutes River without passage below Wickiup Reservoir.