Evaluation of Fish Movement and Water Velocities
Near a Prototype Behavioral Guidance System
at Lower Granite Dam

The Problem

Since 1994, scientists from the Anadromous Fish Ecology Team have been assisting the U.S. Army Corps of Engineers (USACE) in evaluating the migration behavior and passage of juvenile salmon and steelhead through Lower Granite Reservoir and Dam on the Snake River, WA. Understanding the

Figure 1. A three-dimensional view of the primary (bold type) and secondary structures (italic type) at Lower Granite Dam during 2002.

factors that influence the passage of juvenile salmon and steelhead through dams is tantamount to implementing management strategies that may enhance fish passage and improve survival. One concept being tested by the USACE to improve the passage and survival of juvenile salmon and steelhead is surface bypass. Observations at several Columbia River dams have shown that migrating fish use shallow water passage structures in preference to deeper turbine or spillway routes. In 1996, the USACE installed a prototype surface bypass and collector (SBC) at Lower Granite Dam (Figure 1). Radio telemetry and hydroacoustic evaluations in 1996, 1997, 1998, 1999, and 2000 indicated that a large percentage of juvenile salmon and steelhead out-migrants used the SBC relative to the amount of water discharged through the SBC. However, although the SBC was efficient at passing a large percentage of fish per unit of discharge, the SBC was not effective at passing enough juvenile salmon and steelhead to be an effective management tool. In 1998, a behavioral guidance structure (BGS) was added to improve the SBC's performance. The BGS was a 1,100 ft long steel curtain designed to divert fish away from the turbine intakes on the south side of the powerhouse and allow greater opportunity for juvenile salmon and steelhead to discover the SBC's entrances. The BGS diverted 61-92% of radio-tagged fish. However, despite the success of the BGS at diverting fish, there was still an insufficient percentage of fish using the SBC to provide benefit to resource managers. During 2000, studies were designed to test the effect of powerhouse operations on SBC performance. Although certain turbine and spill operation did improve the SBC's performance, the SBC still failed to meet the expectations of resource managers. However, information gained during 2000 indicated that reducing the downward flow below surface bypass entrances might greatly improve the performance of surface bypass structures.

Figure 2. Elevation view of Lower Granite Dam's RSW showing position relative to the existing spill bay during 2002.

As a result, the USACE installed the removable spillway weir (RSW) at Lower Granite Dam during the spring of 2002 (Figure 2). Based on the surface bypass concept, the RSW discharges water at a much shallower depth (~12 ft) than conventional spill bays or turbine intakes (typically 50-70 ft). There are two primary differences between the RSW and the SBC, which may improve performance of the RSW as compared to the SBC. First, the RSW is not located above the powerhouse, allowing the RSW to have no downward flow directly below its entrance. Second, at minimum reservoir elevation (733 ft) the RSW can discharge almost twice the percentage of flow (~8.5%) as the SBC (~ 3.5-5.5%). These two differences may enable the RSW to be more effective at passing a larger percentage of fish than the SBC. If effective, the RSW may reduce fish delay just upstream of dams, provide an alternative route of passage to the turbines, and pass fish with less water than conventional spillways.

Objectives

The goal of our study is to identify the behavior of individual juvenile salmon and steelhead relative to the operation of Lower Granite Dam and the subsequent affect on removable spillway weir performance. The study is designed to obtain the following information: 1) the timing and movement of fish during migration through the reservoir relative to the timing and movement of fish while passing through the dam, 2) the affect of spill and turbine operations on the passage of juvenile salmon and steelhead through the RSW, spillway and powerhouse of Lower Granite Dam, 3) the efficacy of fish guidance structures (e.g. the BGS) and their subsequent affect on the performance of fish passage structures and, 4) determine the relative survival of fish with known passage routes through Lower Granite Dam.

Methodology

Figure 3. Picture of juvenile salmon after being implanted with miniature radio transmitter.

We use radio telemetry to monitor fine scale movements of juvenile salmon and steelhead as they migrate through reservoirs and dams. Fish are collected from seines, fish traps, or from the juvenile fish collection facilities at dams. After collection fish are transported to a tagging site and held in the river for at least 24 h prior to tagging. Fish are surgically implanted with coded radio transmitters (Figure 3). After tagging, fish are held for 24 h in the river before being released. Fish are released about 20 km upstream of the dam, allowing fish to distribute both horizontally and vertically in the water column before approaching Lower Granite Dam.

To monitor fish behavior as they travel through in the reservoir, forebay, and tailrace of dams, we install aerial and underwater antennas that are linked to data logging receivers, providing data collection 24 hours a day, 7 days a week.

Highlights and Key Findings

From 1994-1995, behavior patterns of juvenile chinook salmon and steelhead in the forebay of Lower Granite Dam were described prior to installation of the SBC in 1996 (Rondorf and Banach 1996; Adams et al. 1998). From 1996 to 2000, we tested nine different SBC entrance configurations, a behavioral guidance structure, and four different turbine and spill operations. Although these modifications did not significantly increase the effectiveness of the SBC at passing a sufficient percentage of the fish, the tests revealed two key factors that will likely affect the performance of all surface bypass structures. First, both the lateral and vertical distribution of fish as they approach the dam will determine the likelihood of fish discovering and passing into surface bypass entrances. Second, fish behavior is affected both by time of day (day and night) and dam operations (spill and turbine discharge).

In 2002, the RSW was installed and tested. Results of the 2002 RSW tests indicated that the RSW maybe the best surface oriented passage route ever tested in the Snake River. In short, the RSW discharged about 8.5% of the total discharge through the dam, but on average passed 56-62% of radio-tagged fish determined to pass Lower Granite Dam. In contrast, spill without RSW operation passed comparable percentages of fish (54-66%) as the RSW, but discharged about 35% of the total discharge through the dam. Thus, the RSW was just as effective at passing juvenile salmonids as spill, but passed fish much more efficiently per unit of discharge through the dam. Moreover, the RSW was found to reduce the time for fish to pass the dam and percentage of fish that travel upriver from the dam. Because the RSW offers an alternative route of passage to the turbines, reduces the time for fish to pass the dam, and discharges less water than spill, the RSW may be an effective management option for resource managers in the future.

Where Are We Headed In 2003

In 2003, we propose to study the behavior and survival of juvenile spring chinook salmon and steelhead relative to the performance of the RSW. Specifically, we wish to determine the approach paths and routes of passage at Lower Granite Dam relative to spill conditions, powerhouse operations, and RSW performance. Research activities will be grouped under two objectives. The first objective will determine the timing and route of passage for juvenile spring chinook salmon and steelhead at Lower Granite Dam relative to spill, powerhouse operations, and RSW performance. Under this objective we will release radio-tagged spring chinook salmon and steelhead in Lower Granite Reservoir and monitor the timing and route of passage through Lower Granite Dam during various spill, powerhouse, and RSW operation. The second objective will determine the relative survival of fish with known passage routes through Lower Granite Dam. Under this objective we will release radio-tagged fish in the tailrace of Lower Granite Dam to determine the relative survival of fish that pass through the RSW as compared to the spillway.

Project Contact

Noah Adams
U.S. Geological Survey
Western Fisheries Research Center
Columbia River Research Laboratory
5501-A Cook-Underwood Rd.
Cook, WA 98605-9717

Email: noah_adams@usgs.gov
Phone: 509-538-2299
Fax: 509-538-2843

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