Landsburg Fish Passage Facilities

The construction of the Landsburg Diversion Dam on the Cedar River in 1901 created a migration barrier preventing fish passage into previously occupied habitat between Landsburg and the natural fish migration barrier approximately 12.5 upstream at Lower Cedar Falls. An additional barrier to salmon was created just downstream of the dam by the crossing of the City’s large water supply aqueduct. These facilities were built to provide a reliable supply of high quality municipal water to the City of Seattle and surrounding communities. At the time of their construction, little attention was given to the effects of these facilities on aquatic resources.

Before	After

Reestablishing fish passage into 17 miles of high quality mainstem and tributary habitat in Seattle’s Municipal Watershed upstream of Landsburg Dam is viewed as a key component of salmon recovery efforts in the Lake Washington Basin. The construction of Landsburg fish passage facilities at the dam and aqueduct crossing were completed in 2003. The facilities are comprised of four primary components:

1. A full channel, boulder/chute fishway downstream of the aqueduct crossing to provide easy passage over the aqueduct and improved habitat conditions

2. Fish ladder and sorting facility at the diversion dam, to provide passage for adult salmon and steelhead, adfluvial and resident rainbow and cutthroat trout. Sorting facilities allow the exclusion of sockeye, which, because of their much higher numbers, can pose a risk to drinking water quality.

3. Tip-out downstream passage gate to provide safe passage for downstream migrating fish as they pass over the diversion dam, and

4. Special screens on the municipal water intake to route downstream migrating fish away from the municipal water intake and safely back into the river.

The numbers of fish passing above the dam have generally increased since construction of the passage facilities in 2003. Early monitoring suggests that fish are performing well in this new habitat and recolonization is progressing well.
Fish passage counts from 2003 through 2008
Annual Fish Passage Reports (pdf): 2004, 2005, 2006.
Recolonization Studies