Problem: Each year, endangered juvenile spring Chinook salmon must travel through Fall Creek Dam on their way to the Pacific Ocean, where they eventually mature into adults and then return inland to spawn in their natal streams.
The Corps has usually held Fall Creek Reservoir at a minimum elevation of 728 feet above sea level for flood damage reduction during the rainy winter season. Unfortunately, juvenile fish prefer to swim near the surface, and at that elevation they have a hard time finding a route through the dam due to the depth they must dive – 50 feet or more - to reach the dam’s regulating outlets. In addition, when they do find a route, many are injured due to harsh passage conditions through the dam structure.
The calm waters of the reservoir have also allowed for large accumulations of sediment, wood, sand and gravel. Without the dam, this material would have travelled downstream, providing a natural source of enriching nutrients and spawning gravels for the lower reaches of Fall Creek and the Middle Fork Willamette River.
Solution: To increase juvenile passage and survival through Fall Creek Dam, the U.S. Army Corps of Engineers in 2011 began lowering the elevation of the reservoir for a short period in November or December to 680 feet – only 10 feet above the regulating outlet entrance and near the historical streambed.