Clear Creek Dam Fish Passage

Overview

Figure 1. Satellite view of Clear Creek Dam and Spillway Channel

Fluvial populations of Bull Trout (Salvelinus confluentus) historically existed in the South Fork Tieton River, Indian Creek, and the North Fork Tieton River. However, with the construction of Clear Creek (1914) and Tieton (1925) dams, previously fluvial populations assumed adfluvial life histories where they primarily resided in the newly formed reservoirs (Clear and Rimrock lake, respectively) but generally continued to spawn in their historical spawning tributaries. Both dams were constructed without fish passage and consequently, entrained fish could not return upstream to their natal spawning grounds.  In 1992, a series of fish ladders were constructed in an adjacent spillway channel (Figure 1). The ladders were steep, had extreme hydraulic conditions, and became clogged with gravel. Anecdotal information suggested that fish were unable to ascend the ladders. Amidst growing concern for declining populations of Bull Trout across the western United States, Bull Trout were listed under the Endangered Species Act and ultimately classified as Threatened in 1999.  At the time, there were isolated reports of Bull Trout in Clear Lake and spawning in the North Fork Tieton River. In 2004, biologists documented juvenile and adult Bull Trout in the North Fork Tieton River upstream of Clear Lake, and by 2010, enough genetic samples had been collected to identify a population of Bull Trout in the North Fork Tieton that was genetically distinct from all others in the Yakima River Basin including other adfluvial populations in Rimrock Lake.

Fish Passage Assessments (2012-2016)

Figure 2. Lower Spillway channel with denil ladder clogged with gravel.

Figure 3. Upper Spillway channel with pool and weir ladder.

Figure 4. Seasonal change in daily mean (solid lines), minimum and maximum (dashed lines) water temperatures at the spillway channel (red line) and outlet channel (black line) at Clear Creek Dam.

In 2012, the US Fish and Wildlife Service (Service) and US Bureau of Reclamation (Reclamation) initiated a comprehensive fish passage assessment of Clear Creek Dam with three primary objectives: 1) to determine when North Fork Tieton River Bull Trout attempt to migrate upstream past Clear Creek Dam; 2) to assess their success at doing so under various hydrologic conditions; and 3), to determine post-spawn migration timing and the extent to which the population uses Clear Lake. The study employed a picket weir and box in the North Fork Tieton River to capture post-spawn adults returning from spawning grounds back to Clear Creek Reservoir, as well as hook-and-line angling in the stilling basin below the dam to collect entrained Bull Trout that congregated there. Between 2012 and 2015, a total of 44 adult Bull Trout were captured, implanted with Passive Integrated Transponder (PIT) sampled for subsequent genetic analysis. Tagged fish were monitored using PIT tag detection arrays installed in the fish ladder and the North Fork Tieton River upstream of Clear Lake. Data from tagged fish revealed that none of the 26 fish captured in the stilling basin were able to pass upstream during the study period. Multiple fish tagged in the North Fork Tieton River were observed moving downstream through the spillway channel and ladder, but none were observed passing upstream into Clear Lake (Figures 2 and 3). An independent review of the spillway channel by an engineering contractor revealed extreme water velocities and steep gradients (15-35%). Additionally, water temperatures in the spillway channel exceeded 15°C during summer migration periods, likely deterring Bull Trout from entering. Fish preferred the cooler water of the stilling basin and outlet channel, where temperatures remained below 12°C due to hypolimnetic releases from the dam (Figure 4).

Interim Fish Passage (Trap and Haul)

Figure 5. An adult Bull Trout collected during a trap and haul at Clear Creek Dam with the stilling basin in the background.

In 2016, Reclamation funded the Service to implement an interim trap and haul program until a new fish ladder could be constructed. This program captures and PIT tags Bull Trout collected downstream of Clear Creek Dam and transports genetically identified North Fork Tieton River fish upstream to Clear Lake for release. Tissue samples are collected from fish and a ‘rapid response’ genetic determination conducted by the Service’s Abernathy Fish Technology Center is used to segregate North Fork Tieton River origin fish from other fish (South Fork Tieton River and Indian Creek) that are released downstream of the dam. To date, 141 Bull Trout identified as North Fork Tieton fish have been transported above the dam and released into Clear Lake (Figure 5). An additional 112 Bull Trout identified as South Fork Tieton River or Indian Creek fish that also migrated to the base of the dam were captured and released downstream of the stilling basin.  Fifteen fish identified as Brook Trout/Bull Trout hybrids and have been euthanized.

New Fish Passage

Reclamation and Yakima Basin Integrated Plan (YBIP) partners completed designs for a fish ladder and submerged cool water intake pipe in 2022.  The ladder is designed for upstream migrating Bull Trout, it was built to accommodate future introductions of salmon, steelhead, and existing resident fish. Reclamation and the Washington State Department of Ecology (Ecology) have partnered to implement this project as a component of the Yakima River Basin Water Enhancement Project Phase. The anticipated completion date for Clear Creek Dam fish passage is 2027 with planning for Tieton Dam fish passage underway.