DOWNSTREAM PASSAGE FOR SALMON AT HYDROELECTRIC 

PROJECTS IN THE COLUMBIA RIVER BASIN: 

DEVELOPMENT, INSTALLATION, AND EVALUATION

by 

Richard R. Whitney 

Lyle D. Calvin 

Michael W. Erho, Jr. 

Charles C. Coutant

Prepared for the 

Northwest Power Planning Council 

October 1997 

97-15 
Published October 1997 by the 

Northwest Power Planning Council 

851 SW 6th Avenue, Suite 1100 

Portland, Oregon 97204 

503-222-5161 

Toll Free: 800-222-3355 

The report is available on the Internet at: 

www.nwcouncil.org/library/1997/97-15.htm 

Cover photo: John Day Dam
TABLE OF CONTENTS 

ACKNOWLEDGEMENTS............................................................................................. iii 

EXECUTIVE SUMMARY ..............................................................................................iv 

INTRODUCTION .............................................................................................................1 

DAMS AS OBSTACLES TO MIGRATIONS OF SALMON..........................................5 

DEVELOPMENT OF BYPASS SYSTEMS IN THE COLUMBIA BASIN....................6 

ADULT FISH PASSAGE..............................................................................................6 

MORTALITY OF JUVENILE SALMON IN TURBINES ..........................................7 

MORTALITY OF JUVENILE SALMON IN RIVER REACHES.............................10 

SOURCES OF MORTALITY IN TURBINES ...........................................................14 

SMOLT BEHAVIOR AS IT AFFECTS THEIR BYPASS AT DAMS......................15 

SPILL AS A MEANS OF BYPASS FOR JUVENILE SALMON .............................16 

Normal Spill.............................................................................................................16 

Spill Deflectors – Perforated Bulkheads and “Flip-Lip” Spillways........................18 

Effectiveness of Spill...............................................................................................19 

Surface Spill.............................................................................................................20 

Effectiveness of Surface Spill..................................................................................23 

Implementation of Spill as a Means of Smolt Bypass.............................................23 

MECHANICAL BYPASS SYSTEMS........................................................................24 

Introduction..............................................................................................................24 

Improved Turbine Efficiency...................................................................................25 

Turbine Intake as a Passage Route ..........................................................................25 

Division Barriers Upstream of the Powerhouse ......................................................25 

Fish “Gulpers” .........................................................................................................26 

Gatewell Salvage .....................................................................................................27 

Airlift .......................................................................................................................27 

Gatewell Conduit .....................................................................................................27 

Other ........................................................................................................................28

Turbine Intake Screens ............................................................................................30 

Effectiveness of Fish Bypass Systems: Fish Guidance Efficiency, Mortality, 

Descaling, and Stress...............................................................................................34 

Implementation of Findings on Turbine Intake Screens..........................................43 

Summary of Effectiveness of Bypass Systems........................................................44 

Surface Collection Devices......................................................................................45 

CONCLUSIONS..............................................................................................................49 

APPENDICES .................................................................................................................52 

INTRODUCTION .......................................................................................................52 

APPENDIX A: REQUIREMENTS BY FERC, THE NPPC AND NMFS/NOAA FOR 

INSTALLATION OF MECHANICAL BYPASS SYSTEMS....................................52 

FERC and NPPC Requirements in mid-Columbia ..................................................52 

FERC Requirements for Juvenile Fish Passage including Spill..............................53 

i 
NPPC Requirements in the Fish and Wildlife Program and NMFS/NOAA 

Requirements in the Proposed Recovery Plan.........................................................55 

NPPC AND NMFS/NOAA Requirements for Mechanical Bypass at Snake River 

Projects.....................................................................................................................57

NPPC AND NMFS/NOAA Requirements for Mechanical Bypass at Lower River 

Projects.....................................................................................................................59

APPENDIX B: IN TWO PARTS ................................................................................62 

Part 1. Goals for Juvenile Fish Passage ..................................................................62 

by FERC, NPPC, and NMFS/NOAA ......................................................................62 

Part 2. Evaluation of Fish Passage Achieved in 1995 ............................................65 

SUMMARY.................................................................................................................73 

DISCUSSION..............................................................................................................74 

REFERENCES CITED....................................................................................................76 

LIST OF FIGURES 

Figure 1. Major Northwest Dams......................................................................................3 

Figure 2. Diagram of a typical hydroelectric dam in the Columbia River Basin..............4 

Figure 3. Cross sectional diagrams of the Wanapum Dam sluiceway and spillway.......22 

Figure 4. Cross sectional diagram of Little Goose Dam's turbine intake screen, fyke nets 

 and gatewell area above the screen ..................................................................31 

Figure 5. Wells Dam hydrocombine, as a three dimensional schematic cross section ...47 

LIST OF TABLES 

Table 1. Dates of Closure of Dams on the Columbia and Snake Rivers...........................3 

Table 2. Estimated Mortality of Juvenile Salmon and Steelhead Associated with Passage 

 through Turbines at Hydroelectric Projects in the Columbia River.....................8 

Table 3. Estimated Mortality of Juvenile Salmon and Steelhead in Passing through 

 Reaches of River ................................................................................................12 

Table 4. Estimates of Mortality of Juvenile Salmon and Steelhead in Spill...................17 

Table 5. Sluiceway (Surface Spill) Effectiveness in Passing Fish..................................21 

Table 6. Fish Guidance Efficiency Measured at Columbia Basin Projects ....................36 

ii 
ACKNOWLEDGEMENTS 

We are indebted to John Williams of NMFS/NOAA, Richard Nason and Charles 

Peven of Chelan County P.U.D, and John Ferguson of the U.S. Army Corps of Engineers 

for assistance in locating sources of information. 

We greatly appreciate the cooperation and assistance provided by personnel of the 

Fish Passage Center, particularly, Michelle DeHart, Tom Berggren, Margaret Filardo, 

and Larry Basham in gathering information for the Appendices. 

The authors gratefully acknowledge the editorial assistance of Erik Merrill and 

others on the staff of the Northwest Power Planning Council for their help in preparation 

of the document. 

This report was prepared as part of an assignment from the Northwest Power 

Planning Council to the Independent Scientific Group (ISG) to conduct a review of the 

science underlying the Council's Fish and Wildlife Program. A draft of the present report 

on bypass was included in the prepublication version of the ISG report "Return to the 

River". While the authors listed under the title of the present report were assigned the 

primary responsibility within the ISG for assembling, integrating, and interpreting the 

available information on the subject of bypass, we recognize that all of the other 

members of the ISG participated in its preparation through review of the draft documents 

and exchange of ideas as the analysis progressed, Richard N. Williams, Chair; James A. 

Lichatowich, William J. Liss, Willis E. McConnaha, Phillip R. Mundy, and Jack A. 

Stanford. 
EXECUTIVE SUMMARY 

From 1933 to 1975, development of the hydroelectric system on the mainstem

Columbia and Snake rivers involved construction of a series of major dams. Of these 

dams, Grand Coulee Dam blocked the Canadian portion of the mainstem, and Hells 

Canyon Dam blocked the upper Snake River to migrations of adult salmon (Figure 1). In 

the portions of the mainstem and Snake that are not blocked, there are 13 dams with fish 

ladders that provide passage for adult salmon. These include four on the lower mainstem

Columbia reach, five in the mid-Columbia reach, and four in the Snake River. 70 dams

located on tributaries in the basin are also part of the coordinated hydroelectric system. 

Some of these, such as those on the Cowlitz River, are not passable by salmon, and 

others, such as those above Hells Canyon Dam, lie above impassable dams. Juvenile 

salmon migrating downstream past those projects with fish passage facilities may use 

several routes. They either pass through the turbines, spillways, turbine intake bypass 

systems, navigation locks or ice and trash sluiceways. A few juvenile salmon may pass 

by way of fish ladders designed for adult passage, but these are not designed, located or 

operated in ways that will attract juveniles. Full development of the hydroelectric system

included provisions for storage of spring runoff by dams in the upper tributaries. These 

storage operations distributed flow over the year and reduced the volume of spill 

available for passage of juvenile salmon in the spring, forcing more juveniles to pass 

through the turbines. 

The first measurement of mortality of juvenile salmon in passing through turbines 

came in the early 1950's by Harlan Holmes. He recorded recovery of marked adult 

salmon that had been marked as juveniles and released in two groups, one that passed 

through the turbines and the other that was released below the turbines. Numerous 

studies since then have recorded measurements of mortality between 2.3 and 19 percent 

at various projects, averaging about 11 percent overall. With this rate of loss in passing 

through turbines, fewer than half of the fish migrating downstream from above the 

uppermost projects in the Snake River or upper Columbia River would survive to below 

Bonneville Dam without spill or other passage routes. Mortality in spill averages less 

than 2 percent at projects where losses due to concentrations of predators below the 

spillway are not a factor. 

Numerous methods have been investigated for their potential in diverting the 

juvenile salmon away from the turbine intakes and into a safe passage route. We

summarize those efforts in the text. They include efforts to improve effectiveness of 

spill, barrier nets, fish "gulpers", salvage from gatewells, electric fields, sound, lights, 

louvers, ice and trash sluiceways, turbine intake screens, and surface collectors. Of these 

mechanical devices, only turbine intake screens and surface collectors have proven 

effective enough to justify full installation. 

Spill is effective as an interim measure or as a supplement to a mechanical 

bypass. Effectiveness of spill is measured in terms of the percentage of fish approaching 

the dam that is diverted into spill. Spill effectiveness varies from project to project. 

Application of spill is limited by water quality standards that limit the amount of spill 

because of concern about production by spill of high gas saturation levels that can kill 

fish. Several studies suggest that the effectiveness of spill in passing juvenile salmon can 

be improved. The standard spill gates at projects in the basin are fitted with tainter gates 

iv
that open from below, usually at a depth of around 50 feet below the surface. Provision 

of spill from the surface increases the effectiveness of a given volume of water in passing 

juvenile salmon by a factor of two or more. It has also been learned that spreading spill 

of a given total volume of water (in acre feet) over a 24 hour period passes more than 

twice as many fish as the same number of acre feet of water spilled over a 12 hour period. 

Tests of prototype turbine intake diversion devices have led to the development, 

construction and operation of bypass systems at all of the projects on the mainstem

Columbia River and in the Snake River except The Dalles, Rocky Reach, Rock Island, 

Wanapum and Priest Rapids dams. In Appendix A, we document the requirements of the 

Federal Energy Regulatory Commission (FERC), the Northwest Power Planning Council 

(NPPC), and the National Marine Fisheries Service (NMFS/NOAA) for installation of 

bypass systems at each project. We also provide information on the status of those 

bypass facilities and future installation schedules at each of the 13 projects. Future 

installation is scheduled at The Dalles, Wanapum and Priest Rapids Dams, and is under 

study at Rocky Reach and Rock Island dams. Meanwhile, The Dalles Dam uses the ice 

and trash sluiceway to pass at least 40 percent of the juvenile salmon approaching the 

dam and more when spill is added. Turbine intake screens have been the primary choice 

by the Corps of Engineers (Corps) at their projects. The Corps has a schedule for 

replacement of standard length screens with extended-length screens at all eight of their 

projects, including The Dalles. As an example of the cost of these measures, in 1992 the 

Corps budgeted $32 million for development and installation of intake diversion screens. 

This program has been ongoing since the 1960's (Corps, 1992). 

Effectiveness of turbine intake screens is measured by fish guidance efficiency 

(FGE), which is the percentage of fish approaching the turbine intakes that is diverted by 

screens. Measured fish guidance efficiency differs from project to project and with 

respect to other factors, which include the design of the screen, the species of salmon, 

degree of smoltification, time of day, and progress of the season. Extended length 

screens have achieved higher measured fish guidance efficiency than standard length 

screens. Fish guidance efficiency of extended length intake screens, although at times 

reaching values as high as 93 percent for steelhead and coho and 88 percent for chinook 

yearlings, are for the most part below 50 percent for subyearling chinook and sockeye. 

Fish that are not guided will pass through the turbines. Fish guidance efficiency appears 

to have reached an upper limit that is less than the surface collector at Wells Dam. Intake 

screens are unlikely to prove 100 percent effective in diverting juvenile salmon (Office of 

Technology Assessment, 1995, p.127). The 1987 Fish and Wildlife Program of the 

NPPC set a standard of 90 percent fish guidance efficiency for intake screens - “if it can 

be achieved." It appears that this standard can not be achieved. 

Fish that are successfully guided by the screens into the bypass conduits are 

subject to injury at the screen and within the bypass system. The Fish and Wildlife 

Program of 1994 specified a criterion of 98 percent smolt survival within bypass and 

collection systems from the screen to the end of the outfall. This standard appears to be 

attainable. However, losses due to predation at the outfalls and in the tailraces can be 

substantial in some situations. 

While fish guidance efficiency focuses on measurement of effectiveness of 

mechanical devices in diverting fish away from turbine intakes, fish passage 

effectiveness (FPE) is a measurement of the total percentage of fish that pass a project by 

v 
routes other than the turbines. Passage can be through spill, the ice and trash sluiceway, 

or through the intake bypass system with the aid of screen diversion. In other words fish 

passage efficiency focuses on fish that are diverted away from the turbine intakes and 

into a safer passage route. Both NMFS/NOAA and the NPPC have established goals of 

80 percent fish passage which includes all salmon species in both spring and summer. 

The most successful bypass system in the basin is at Wells Dam where a surface 

collector passes an estimated 89 percent of the juvenile salmon in both spring and 

summer. Thus, it is the one project in the basin with a bypass that can achieve the 80 

percent fish passage goal. Feasibility of using surface collectors at other projects is being 

investigated by the Corps, and by Chelan and Grant County Public Utility Districts. 

In Appendix B, we compare the goals for fish passage of FERC, NPPC, and 

NMFS/NOAA with what was achieved in 1995. Experience in that year serves as an 

example illustrating that, except at Wells Dam, the NPPC and NMFS/NOAA goals of 80 

percent fish passage can not be achieved without the addition of spill, due to limitations 

of performance of turbine intake screens or ice and trash sluiceways that are present. 

Furthermore, the amounts of spill required to meet the goals can not be provided due to 

gas saturation limits required by water quality standards. 

To compare the performance of the fish passage measures as required in the 

NMFS/NOAA Proposed Recovery Plan with what was actually achieved, estimates of 

fish passage achieved at each of the Snake River and lower Columbia River projects in 

1995 were produced by the Fish Passage Center (1995). (See Appendix B.) Under the 

NMFS/NOAA requirements, highest fish passage, 78 percent, was achieved at The 

Dalles Dam (Fish Passage Center, 1995). With the exception of Bonneville Dam at 55 to 

62 percent, all of the lower river projects achieved fish passages in the 70 percent range. 

Snake River projects, with the exception of Ice Harbor Dam, achieved fish passages 

between 50 to 60 percent. Ice Harbor Dam achieved an estimated 79 to 84 percent fish 

passage, but with excessive spill. 

Therefore, the 80 percent fish passage goals of NMFS/NOAA or the NPPC can 

not be achieved in the river reaches where endangered Snake River fish are present. The 

fish passage goals were achieved at Ice Harbor Dam in 1995 but only because turbine 

outages led to inadvertent spill in amounts that caused gas saturation to exceed limits. 

With respect to FERC requirements, which apply in the mid-Columbia reach, the 

fish passage requirements at Wells Dam of 70 percent in spring and 50 percent in 

summer were exceeded by the 89 percent measured. The FERC requirement of 50 

percent fish passage at Priest Rapids Dam in summer was met (62 percent) by provision 

of spill alone. Fish passage requirements by FERC at Wanapum Dam and at Priest 

Rapids Dam in summer could not be met because of limitations on spill due to gas 

saturation limits for water quality. FERC requirements were met at Rocky Reach and 

Rock Island dams, as they are specified in terms of spill amounts, not fish passage. The 

NPPC fish passage requirement of 80 percent, which applies as well as FERC 

requirements in the mid-Columbia reach, was met only at Wells Dam. 

Calculation of the amount of spill required to achieve the 80 percent fish passage 

goal in the Snake River and lower Columbia River is complicated, requiring assumptions 

that go beyond available data. Decisions on the appropriate fish guidance efficiency to 

use depend upon predictions of the mix of species and other factors. Spill effectiveness 

curves are lacking for most of the Corps projects, requiring an assumption of a 1:1 

vi
relationship between percentage of flow that is spilled and the percentage of fish passed. 

This assumption is not met where adequate data are available for analysis, such as at John 

Day and The Dalles dams. 

The calculated spill amounts in the Detailed Fishery Operating Plan depend upon 

an assumption (or conclusion) that there is an advantage to spilling 12 hours at night 

versus 24 hours a day as a benefit to power production. We question this assumption. 

We believe a more detailed analysis of costs and benefits to fish and power would be 

warranted. In any case, the spill amounts calculated for use by NMFS/NOAA can not be 

provided in practice due to limitations on gas saturation levels. This in spite of the fact 

that for the duration of the juvenile migration period water quality standards were 

expanded to permit 120 percent saturation. In addition, by 1995, five of the eight federal 

mainstem and Snake River projects were at least partially equipped with flip lip spillway 

deflectors designed to reduce gas saturation levels. (See Appendix A.) The 

NMFS/NOAA Proposed Recovery Plan specifies an upper limit of 115 percent gas 

saturation in the forebays of the projects. This standard can not be met at all during 

normal spring runoff. 

Analysis by the Fish Passage Center indicated that survival of PIT tagged juvenile 

chinook salmon was not adversely affected by gas saturation levels experienced in 1995, 

which were 130 percent to 138 percent from May 25 to June 8 at Ice Harbor Dam (Fish 

Passage Center, 1995). Further studies are needed of juvenile salmon survival in natural 

river situations where gas saturation levels are high. 

Future developments of juvenile bypass are expected to be in surface collectors, 

ice and trash sluiceways, and surface spill, all of which take advantage of a natural 

surface orientation of juveniles. Measures are needed to reduce gas saturation levels 

associated with spill levels that are required to meet fish passage goals. 

vii 
INTRODUCTION 

Development of the hydroelectric system in the Columbia River Basin began in 

the late nineteenth century on the tributaries. The first dam on the mainstem Columbia 

River was Rock Island Dam, completed in 1933, Figure 1, followed soon by Bonneville 

Dam in 1938 and Grand Coulee Dam in 1941, Table 1. Grand Coulee Dam blocked the 

Canadian portion of the upper Columbia River to migrating adult salmon. Hells Canyon 

Dam, completed in 1967, blocked the upper Snake River to salmon passage (Petersen, 

1995). There are now thirteen dams on the mainstem Columbia and Snake Rivers that 

are passable by salmon. Additional hydroelectric projects on the tributaries bring the 

total to 211 dams in the Columbia River Basin of which 83 are part of the coordinated 

power system (Interagency Team, 1991; Logie, 1993). Some of these are impassable to 

salmon or are above dams that are impassable. In 1964, the United States and Canada 

agreed to a treaty that established the goal to develop the potential of the Columbia River 

and its tributaries to the mutual advantage of both countries (Bonneville Power 

Administration, 1980). As a result of the treaty, two Canadian mainstem dams, three 

Canadian tributary dams, and two Montana projects were built. Hydroelectric power 

generation, flood control, and irrigation were the benefits identified by the U. S. Army

Corps of Engineers and the Bureau of Reclamation (Logie, 1993). 

By 1976, the Bonneville Power Administration (BPA)(1980) could say that the 

Columbia River was fully developed for hydroelectric generation. The Hanford Reach, 

the one remaining undammed portion of the river, was debatable as a potential site, due 

to the potential for flooding of underground storage facilities for atomic wastes at the 

Hanford Reservation. Average annual discharge from Bonneville Dam, lowermost dam

on the river, is 183,300 cfs (Interagency Team, 1991). Total storage capacity of the 

reservoirs in the system amounts to 55.3 million acre feet (68.2 billion m3

), which is 

about 25 percent of the basin's average total annual runoff (Logie, 1993; Thomas, 1997). 

This capacity is used to store a portion of the spring freshet for the benefit of later power 

production, and drawdown in late winter and early spring for the benefit of downstream

flood control and other purposes (Logie, 1993). As a comparison, storage capacity in the 

Colorado River is about four times the average annual runoff in that system (Thomas, 

1997). 

1 
2 
Figure 1. Major Northwest Dams 

(Source: Interagency Team, 1991)

Table 1. Dates of Closure of Dams 

on the Columbia and Snake Rivers 

(Source: Interagency Team, 1991)

Project Name Columbia Snake 

Swan Falls 1901 

Lower Salmon Falls 1907 

Upper Salmon Falls 1932 

Rock Island 1933 

Bonneville 1938 

Grand Coulee 1941 

Bliss 1948 

C. J. Strike 1952 

McNary 1954 

Chief Joseph 1955 

Brownlee 1958 

The Dalles 1959 

Priest Rapids 1959 

Rocky Reach 1961 

Oxbow 1961 

Ice Harbor 1961 

Wanapum 1963 

Wells 1967 

Hells Canyon 1967 

John Day 1968 

Keenlyside 1968 

Lower Monumental 1969 

Little Goose 1970 

Mica 1973 

Lower Granite 1975 

Revelstoke 1983 

3 
Figure 2. Diagram of a typical hydroelectric dam in the Columbia River Basin that shows the spillway (A and in

powerhouse to the right of the spillway, powerhouse cross section (area F in the circular inset), and the navigatioof the spillway (not present in mid-Columbia dams). In the powerhouse cross section, fish are shown moving up the powerhouse, while the water continues on through the turbine. The diagram also shows the powerhouse tailraladder exit and entrance (E on the right), and navigability (G). 

4 
DAMS AS OBSTACLES TO MIGRATIONS OF SALMON 

As the nearest large river to the north, the Fraser River stands as an example 

where experience with salmon is useful for comparison with experience in the Columbia. 

In 1960 at the behest of the International Pacific Salmon Fisheries Commission, Andrew 

and Geen undertook an analysis of the probable effects of hydroelectric development in 

the Fraser River, British Columbia on salmon production in the Fraser system. The 

proposed development would have involved construction of 18 dams on the mainstem

and 44 on tributaries. They concluded that, 

 

“Dam construction presents a serious threat to the continued expansion - and 

indeed the very existence - of the commercial and recreational value of the Fraser 

River fisheries resource.... Although the fish-dam problem has existed for 

centuries in many countries, no practical solutions have yet been found that afford 

complete protection for anadromous fish in rivers obstructed and altered by large 

dams.” (Andrew and Geen, 1960, p 2). 

 

Largely on the basis of their conclusions, the Fraser River mainstem remains undammed 

to this date. Although their study was completed 37 years ago, their conclusion that no 

practical solution to the fish-dam problem has yet been found still applies, as borne out 

by experience in the Columbia River which is summarized below. 

The typical mainstem dam on the Columbia River presents challenges to the 

migrations of both juvenile and adult anadromous fishes. The mainstem dams are for the 

most part around 100 feet high, although Rock Island Dam is about 50 feet high, while 

Grand Coulee and Hells Canyon dams are over 300 feet high and are impassable to fish. 

Juvenile emigrants, moving downstream in the direction from left to right in Figure 2, 

may pass the project by one of four basic routes: the powerhouse, the spillway, the 

navigation channel, or the fish ladders. As seen in a cross section of the powerhouse 

(inset Circle, Figure 2), when following the flow of the water onto the upstream face of 

the powerhouse, juveniles are forced to dive in order to follow the water flow (Arrows 

below point F in the inset) into the entrance to the turbine gallery. (Some projects, such 

as The Dalles Dam, have an ice and trash sluiceway adjacent to the powerhouse which 

passes some juveniles.) If the project has a bypass, the juveniles may encounter a screen 

which sends them upward in gatewells toward the upper deck of the powerhouse (Up 

Arrow, below Point F) and into a series of passages connecting the gatewells that will 

bring them out of the powerhouse to below the dam in the vicinity of Area D (Figure 2). 

Juveniles that miss the screen continue on through the turbine and exit near the 

downstream side of the powerhouse in the vicinity of Point D (the Tailrace). Note that 

point D describes the same basic area in both the circular inset and the main drawing. 

Fish ladders are provided for adults moving upstream and are not used by juveniles to a 

significant degree. Most likely, the relatively small volume of water in the ladders and 

their location make it difficult for the juveniles to find them. The five projects in the 

mid-Columbia reach do not have navigation channels. 

Compensation for losses of salmonids due to construction and operation of the 

hydroelectric system has been attempted primarily by hatchery production, and to a much 

5 
lesser extent by habitat improvement, which is considered to be in its developmental 

stages. Mitigation at the projects of mortalities experienced by juveniles migrating 

downstream has been attempted primarily by construction of bypass systems for juvenile 

salmon at the dams, and by provision of a "water budget" for facilitating movement of 

juvenile salmon out of the system (NPPC, 1984). Transportation of juvenile salmon by 

truck and by barge is in fact part of the bypass system because it depends upon the 

bypass system for collection of fish moving in the river. This report deals with the 

subject of development and operation of bypass systems. This report does not address 

other subjects, including the water budget or transportation of juveniles. 

The significance of bypass facilities for juvenile salmonids can perhaps be judged 

by the fact that the Corps of Engineers budgeted $32 million in 1992 for development 

and installation of diversion facilities, a program that has been ongoing since the 1960's 

(Corps, 1992). 

DEVELOPMENT OF BYPASS SYSTEMS IN THE COLUMBIA BASIN 

ADULT FISH PASSAGE 

Federal law, dating from 1906, authorizes the United States Departments of 

Commerce (and/or Interior now) to require fishways at all federally licensed dams

(Office of Technology Assessment, 1995). Accordingly, passage for adult salmon was 

provided at the time of construction at the five dams licensed by the FERC in the midColumbia reach. In addition, when Congress authorized the non-federally licensed dams, 

those constructed and operated by federal agencies (U.S. Army Corps of Engineers and 

U.S. Bureau of Reclamation), they required adult fish ladders at the time of construction 

at all except Grand Coulee Dam and Chief Joseph Dam. Those dams were thought to be 

too high to have effective ladders. In addition, Grand Coulee Dam was planned for 

irrigation and flood control, both of which require extensive fluctuations in pool 

elevation that was considered to make a fish ladder (of standard design) unfeasible. Hells 

Canyon Dam, constructed by Idaho Power Company on the Snake River included 

provision for fish passage that was not successful (Petersen, 1995). In the basin, 

impassable dams have blocked salmon from about 35 percent of their former habitat 

(NPPC, 1987). 

While in general adult passage facilities are considered to be effective in design 

and operation, questions remain about possible delays in movement of adults 

approaching and passing through the ladders (Mighetto and Ebel, 1995). Chapman, et al. 

(1994) concluded that, while the analysis is complicated by fall-back of fish that are 

counted twice, the best estimate is a 5 percent loss of adult chinook between dams. This 

loss is due to several factors including harvest, mainstem spawning, fish turning into 

tributaries, and fish not locating ladder entrances. Bjornn and Peery (1993) reviewed the 

literature relating to factors affecting movement of adult salmon through dams and 

reservoirs on the lower Sanke River. Studies have shown that levels of spill can lead 

either to reduced time spent in passage at a dam with low spill levels relative to no spill 

or increased time spent with high spill levels relative to low spill. (Also see Dauble and 

Mueller, 1993). Mendel, et al. (1993) discuss factors affecting upstream migrations of 

adults into the Snake River. Recent advancements in the technology of tracking radio 

6 
tagged adults has made it possible to closely track individual adult salmon as they 

approach and transit dams and fish ladders (e.g. Stuehrenberg, et al., 1995, Swan, et al., 

1994). Studies are under way or in the process of interpretation. It is hoped that they 

will lead to identification and correction of any problems in adult passage that might exist 

at particular projects. 

MORTALITY OF JUVENILE SALMON IN TURBINES 

While the need for adult passage was obvious, the need to provide downstream

passage for juvenile salmon was questioned by some (Office of Technology Assessment, 

1995; Petersen, 1995). That the contrary point of view was given some attention is 

shown by the fact that four downstream migrant bypass facilities were provided at 

Bonneville Dam when it was built in 1938 (Andrew and Geen, 1960; Bell, et al., 1967). 

Although we can find no description of them, they were apparently surface collection 

devices used in conjunction with screened water intakes. They were placed at the north 

end of the spillway and south end of the powerhouse where it was hoped they would 

attract juvenile migrants away from the turbines or spillway (Mighetto and Ebel, 1995). 

They were found to be ineffective for that purpose by the Corps of Engineers’ biologist, 

Ivan Donaldson (Mighetto and Ebel, 1995), and by the 1950s were being used primarily 

to obtain samples of fish moving past the project (Anas and Gauley, 1956). 

The need to provide passage for juvenile salmon was first established as a result 

of a set of experiments conducted by Harlan Holmes at Bonneville Dam from 1938 to 

1948. These experiments showed a loss of 11 to 14 percent of juveniles in passing 

through the turbines (Bell, et al., 1967). Holmes used juvenile fish in paired groups, one 

released below the dam as a control and the other released into the turbine intake. He 

then compared the relative rates of return of the adults from those groups. Some Corps 

officials at that time were skeptical of the results (Petersen, 1995, p.110), but there is no 

longer any doubt that turbines cause loss of fish in passage. However, some may 

question the values Holmes measured. More information on that point is provided below. 

Once Holmes had established a reference point, it was then possible to proceed 

with methods using recovery nets in the tailrace and other techniques that did not require 

waiting years for the adults to return. Verification by other investigators soon followed 

(Schoeneman and Junge 1954, 1959; Schoeneman, 1956; Schoeneman, et al., 1961). 

Available estimates of mortality of salmonids in turbines range from 2.3 to 19 percent 

(see Table 2). There is considerable variability in survival estimates from one project to 

another. This variability should be taken into account in modeling survival of juvenile 

salmon in downstream passage. 

7 
Table 2. Estimated mortality of juvenile salmon and steelhead associated with passage through turbines a

projects in the Columbia River (Sources: Bell, et al., 1967; DeHart, 1987: Others, more recent, are named 

D

a

m

M

o

rtality

Y

e

a

r

A

uth

o

rs S

p

e

cies

Bonneville I (1993) 11% to 15% 1938-1948 Holmes (1952), per Mighetto and 

Ebel, 1995) 

Chinook Subyea

4% 1954 

W

eber (1954, See Iwamoto and 

Williams, 1993) 

Chinook Subyea

Bonneville II 2.3% or 

9.5%* 

1988-1990 Gilbreath, et al. (1993) Chinook Subyea

John Day 13% 1980 Raymond and Sims (1980) Chinook YearlinMcNary 11% ** 1955; 1956 Schoenem

an, et al., (1961) Chinook Subyea

Ice Harbor 10% to 19% 1968 Long (1968) Coho “fingerlinLower Monumental 16% 1975 Long, et al., (1975) Coho (20-22/ lb

3.5% 1994 Muir, et al., (1995A) Chinook Yearlin

Lower Granite 16.9% *** 1987 Giorgi and Stuehrenberg, (1988) Chinook YearlinLittle Goose 8% 1993 Iwamoto, et al., (1994) Chinook YearlinW

ells 16

% 1980 

W

eitkamp, et al., (1980) Steelhead 

Rock Island No. 2 (Bulb Turbines) 

5.7% or 13%  

1979 Olson and Kaczynski (1980) Coho and Steelh

Big Cliff (North Santiam River; Tributary to the Willam

ette River) 

11% **  1957 Schoenem

an, et al., (1961) Chinook (Yearli

Subyearlings) 

13.5% 1957 Oligher and Donaldson (1965) Chinook Yearlin11.8% 1964 Oligher and Donaldson (1966) Chinook Yearlin8.6% 1966 Oligher and Donaldson (1966) Chinook Yearlin

8 
Estimates using radio tagged salmon recovered immediately in the tailrace (HI-Z Turb’n Tag, Heisey, et a

D

a

m

M

o

rtality

Y

e

a

r

A

uth

o

r

S

p

e

cies

Rocky Reach Dam Variable blades 7% 1994 RMC Env. Serv. and Skalski (1994) Chinook Yea Fixed blades 3.9% 1994 RMC Env. Serv. and Skalski (1994) Chinook YeaLower Granite Dam 5.2% 1995 Normandeau Associates, et al., (1995) Chinook Yea*Gilbreath, et al. (1993) provide data that produce a weighted average estimate of 2.3 percent m

ortality over thre

fish released in the tailrace are used as reference controls. If fish released near the Hamilton Island Boat Launch as the reference controls, the estimate is 9.5 percent. Their data show that, in the two years for which there are creleased in the tailrace experienced an additional 6.8 percent m

ortality relative to the downstream release. In 198

in the spillway. They survived at a higher rate than the fish released in the tailrace and at the sam

e rate as the fis

downstream. Therefore, the difference between the two estimates of m

ortality in turbines can be explained by th

estimate includes an element of m

ortality in the tailrace. Fish passing through the spillway were not exposed to 

m

ortality. It appears that in the tailrace at Bonneville Dam there are peculiar back eddies or shore areas where th

concentrations of predators (Ledgerwood, et al., 1994).  **Schoenem

an, et al. (1961) found no significant difference between the 1955 estimate of 13 percent and the 19

percent m

ortality at McNary Dam, and combined them to get the 11 percent estimate. Similarly, they combined 

for yearlings and subyearlings.  ***Giorgi and Stuehrenberg (1988) felt that their estimate was on the high side due to failure of test and control recovery sites, as required by the experim

ental protocol. However, their estimate agrees with the later one of Iw

****There was a dispute over the results of this study at Rock Island. The point estimate was 5.7 percent m

ortal

com

mittee appointed to review the study found that there was no significant difference between that estimate and 

Cliff and McNary dams, (Chapman, et al., 1980). Nevertheless, the administrative law judge for FERC found in percent estimate, but ordered development of a bypass system, (Rock Island Project, 34 FERC 63,044 at 665,167

9 
While oversimplifying the situation, an overview can be useful for the purposes of 

this report. The average of the first group of 18 estimates that used comparable study 

methods is 10.9 percent mortality. Estimates from three studies that used a radio tagging 

system that allowed quick recovery of marked fish in the tailrace are lower than most of 

the others. Estimates for these three ranged from 3.9 percent to 7 percent (RMC 

Environmental Services, Inc. and Skalski, 1994 and Normandeau Assoc., et al., 1995) 

and averaged 5.5 percent. The lower estimates most likely estimate mortality directly 

associated with turbine passage, while the others probably include factors beyond the 

turbine. 

It is apparent that a portion of the mortality measured in some of the studies 

occurred in the tailrace or downstream, rather than in the turbines themselves. For 

example, see the Table 2 footnote that is a review of data from a study by Gilbreath, et al. 

(1993) at the Bonneville Dam Powerhouse II. In addition to losses of juvenile salmon in 

direct turbine passage, losses have been identified in intake and discharge structures, the 

tailrace, or reservoir, and losses due to predation as an incidental effect of turbine passage 

or other losses not directly assignable to turbine effects, (Long, et al., 1975). Other 

factors that affect mortality of salmonids in turbines will be discussed below. 

MORTALITY OF JUVENILE SALMON IN RIVER REACHES 

Studies designed to measure mortality of juvenile salmon in river reaches are 

summarized in Table 3. A set of studies conducted over three different years in the midColumbia found an average of about 15 to 16 percent mortality from one project to the 

next for juvenile chinook salmon passing each of the five projects in the mid-Columbia. 

This included mortality in the turbine, tailrace, and reservoir (Chapman and McKenzie, 

1980; McKenzie,, et al., 1982; McKenzie, et al., 1983).1

 Similar system-wide mortality 

estimates of 20 to 25 percent per project were derived for the Snake River and lower 

Columbia (Raymond 1979; Sims, et al. 1984). Steward (1994), and Williams and 

Mathews (1994) have questioned the validity of the early series of Snake River and lower 

Columbia River estimates. On the other hand, Giorgi and Stuehrenberg (1978) estimated 

mortality of chinook in the reach through the reservoir at Lower Granite Dam to the 

tailrace at Lower Granite Dam to be 18 percent in 1978. 

In any case, these estimates are no doubt higher than in today's system with 

improved bypass systems in place at all of the dams (NMFS/NOAA, 1995 p V-2-3; NRC, 

1995). Bypass system improvements include construction of bypass facilities at Lower 

Granite and Ice Harbor dams, modifications of bypass facilities at Little Goose and 

Lower Monumental dams, removal of debris from collection systems, installation of fliplips in spillways to reduce gas supersaturation, changes in turbine operations, and 

implementation of the water budget. The conclusion that survival is now higher is 

supported by the studies of Iwamoto, et al. (1993) and Muir, et al. (1995). The “PIT 

Tag” (Prentice, et al., 1992) is a new technology that has made possible studies such as 

the latter two that can provide estimates of survivals through given “reaches” or segments 

 

1

 The 1980 study produced a higher estimate (20 percent), but there were difficulties in execution of the 

study design, which called for release groups to arrive at downstream recovery sites at near the same time, 

which they did not do (Chapman and McKenzie, 1980). 

10 
of the river, where detectors are located at both ends. The proposed procedure for 

developing such estimates in the Columbia Basin, based on a concept referred to as the 

Cormack-Jolly-Seber concept (See Burnham, et al., 1987) was first outlined in a 

document prepared by Skalski and Giorgi (1992). This resulted in the Snake River 

studies by NMFS and the University of Washington in 1993 and 1994 (Iwamoto, et al., 

1993; Muir, et al., 1995A).2

 Their estimates of mortality of juvenile chinook in passing 

through reservoir to tailrace of three projects in the Snake River in 1993 and 1994 ranged 

from 8 to 22 percent per project and are probably site specific, Table 3. In 1994, 

mortality of naturally produced chinook in passing through the full length of the reach 

from the reservoir at Lower Granite to the tailrace at Lower Monumental Dam was 

estimated to be 27 percent (Muir, et al., 1995A). On a per project basis, mortality would 

amount to a little less than 10 percent, which is in the range of their other estimates. 

 

2

 The estimation method employed by Iwamoto, et al. (1994) and Muir, et al. (1995) had been questioned, 

but at the request of the NWPPC the ISG supervised a review (Independent Scientific Group, 1996). The 

ISG report concluded that the procedure was the best available method for estimating survival rate in

reaches. 

11 
Table 3. Estimated Mortality of Juvenile Salmon and Steelhead in Passing Through Reaches of River 

 (Sources: Originals as cited, and Bevan, et al., 1994) 

For Hatchery Chinook River Reach Mortality Years/Author 

Mid-Columbia 15%-16% per project (five 

projects) 

Chapm

an and McKen

McKenzie, et al. (19(1983) 

Through Lower Granite Reservoir from Asotin 18% Giorgi and StuehrenbLower Granite Reservoir from Asotin to Various Downstream Locations 

10% Iwamoto, et al. (1994

To tailrace at Lower Granite 8% Muir, et al. (1995) From Lower Granite to tailrace Little Goose 14% Iwamoto, et al. (1994

21% Muir, et al. (1995) 

From Little Goose to tailrace Lower Monumental 11% Muir, et al. (1995) For Hatchery Steelhead Lower Granite Reservoir from Asotin to various downstream locations To tailrace at Lower Granite 10% Muir, et al. (1995) From Lower Granite to tailrace Little Goose 22% Muir, et al. (1995) From Little Goose to tailrace Lower Monumental 17% Muir, et al. (1995) For Naturally Produced Chinook From Lower Granite Reservoir to Lower Monumental tailrace

27% Muir, et al. (1995)

Table 3 (Continued) Estimated Mortality of Juvenile Salmon and Steelhead in Passing Through Reaches o

12 
(Sources: Originals as cited, and Bevan, et al., 1994) 

For Naturally Produced and Hatchery Chinook. [The following figures are taken from the Draft Snake River Salmon Recovery Plan (Bevan, et al., 1994). They by Steward, (1994), Williams and Mathews, (1994), and NRC, (1995, p. 201) who concluded that system and avm

ortalities were overestimated. For the purposes of the Draft recovery plan and our purposes here, they should b

values that provide a com

parison of survival before and after Little Goose and Lower Monumental dams were ad

any case they are not relevant to the system as it now exists, as explained in the text.] From Salmon River to Ice Harbor Dam: Before and after Little Goose and Lower Monumental Dams WeY

e

a

rs Estim

ate

d

M

o

rtality

A

uth

o

r

Before 1970 11% Raymond (1979)After 1970 67% Raymond (1979)From Lower Granite to The Dalles Before and After Little Goose, Lower Monumental and Ice Harbor WeB

efore

3

7

% Raymond (1979)

After 80% Raymond (1979); Sim* This study was designed to test the m

ethod and associated assu

m

ptions, not to produce survival estimates. Nev

resulting estimates are close to those in the later study. 

13 
Conditions in the mid-Columbia reach have also improved since the studies of 

Chapman and McKenzie (1980) and McKenzie, et al. (1982, 1983) were conducted. 

Wells Dam has a fully functioning bypass system, as well as new turbines with higher 

efficiency ratings, and the other mid-Columbia projects have added spill amounts as 

bypass routes for juvenile salmon. These factors are discussed in more detail below. 

The new estimates of mortality in turbines and the estimates of survival in reaches 

of the river have brought into focus the need to be able to separate direct mortality 

induced upon juvenile salmon in the turbines from mortality experienced as an indirect 

result of turbine passage or from other causes. The ability to separate is necessary 

because the solutions will differ. There have been several attempts to separate mortality 

estimates into components for the reservoir and tailrace. Iwamoto, et al. (1993) 

developed a specific estimate for mortality in the reservoir above Lower Granite Dam,

which was based on a series of reach survival estimates applying from a point above 

Lower Granite Dam to the tailrace at little Goose Dam. Iwamoto, et al. also developed 

estimates of survival in turbines at both dams. The study produced an estimate of zero 

mortality for yearling chinook in the reservoir above Lower Granite Dam in 1993. Muir, 

et al. (1995A) developed an estimate of steelhead smolt mortality from the forebay at 

Lower Monumental Dam to the tailrace, amounting to 42 percent, a surprisingly large 

number. Unfortunately, there seems to be no estimate of mortality of steelhead in 

turbines for Lower Monumental Dam. However, even assuming the worst, say 20 

percent mortality in the turbines, the result indicates a high loss of juvenile steelhead in 

the forebay. At Bonneville Dam, mortality of subyearling chinook in the tailrace 

downstream to the Hamilton Island Boat Launch was estimated to be 10.5 percent 

(Dawley, et al., 1989). The data of Johnsen and Dawley (1974) can be used to estimate a 

54.5 percent loss of juvenile salmon from the tailrace at Bonneville Dam to Rainier 

Beach, Oregon. These studies indicate that in some instances losses of juvenile salmon 

in the forebay and tailrace exceed the losses in turbines. 

Studies of predation by squawfish also indicate that the highest losses occur in the 

forebays and tailraces of the dams (Gadomski and Poe, 1993). Birds are particularly 

troublesome in the tailrace. Predation losses are discussed in a separate section of Return 

to the River (Williams, et al., 1996). As an example, Gadomski and Poe (1993) 

estimated a loss of 1.4 million juvenile salmon in John Day reservoir due to squawfish 

predation in 1993. 

SOURCES OF MORTALITY IN TURBINES 

Existing physical models of turbine facilities were used in studies designed to 

explore the factors responsible for the smolt mortality associated with turbine passage, 

such as those of Cramer (1960, 1965), and Cramer and Oligher (1960, 1961). Further 

extensive, pertinent literature on the subject is summarized by Bell, et al. (1981); 

Turbak, et al. (1981); Lucas (1981); Bell (1991); and Cada, et al. (1997). 

Bell, et al. (1981) and Bell (1991) summarized the findings as follows. Fish 

survival is related to the efficiency curve of propeller type turbines. Highest survival 

occurs at highest efficiency. All of the Columbia River and Snake River Powerhouses on 

the portion of the river passable by salmon are equipped with propeller type turbines. 

Turbines with negative pressure within the draft tube have a higher kill rate than those 

14 
with positive pressure, pointing to the importance of maintaining an optimum tailwater 

elevation. Clearances between the runners and their surroundings are a potential source 

of mortality. 

Remedies to the turbine passage problem were sought through the decades of the 

1960’s and 1970’s (Mighetto and Ebel, 1995). Best turbine operating criteria were 

defined, i.e. - operate at the upper end of the turbine efficiency curve. Design 

characteristics were analyzed - minimize negative pressures in the draft tube, and avoid 

clearances around runner blades that could impact fish (Bell, et al., 1967). At the same

time, efforts were continued to develop methods for diverting fish away from the turbine 

intakes. 

SMOLT BEHAVIOR AS IT AFFECTS THEIR BYPASS AT DAMS 

The preponderance of evidence demonstrates that juvenile salmon migrating 

downstream are oriented to the upper portion of the water column. Giorgi and Stevenson 

(1995) reviewed much of the evidence at Corps projects. Johnson (1995) reviewed the 

evidence from salmon literature world-wide. When juvenile salmon encounter a dam,

they prefer surface outlets, when available, and are reluctant to sound. Raymond and 

Sims (1980) found that juvenile salmon passing through gates with surface spill were as 

likely to pass in the day as at night. In comparison, juvenile salmon sampled from the 

turbine intakes, the ceilings of which were located at about the same depth as the bottoms

of the unlogged spill bays, showed a strong peak at night. This finding suggested that 

juvenile salmon approaching the dam delayed sounding to the intakes until after dark, 

and that they more readily passed through surface spill. 

The number of juvenile salmon in the ice and trash sluiceway at The Dalles Dam

peaked around mid-day (Nichols, 1979; Nichols and Ransom, 1980, 1981; Steig and 

Johnson, 1986; and Johnson, et al., 1987). At Bonneville Dam, the number also peaked at 

mid-day (Willis and Uremovich, 1981). (All as summarized by Giorgi and Stevenson, 

1995.) This is in contrast to turbine intakes where the number of juvenile salmon reaches 

a peak at night (Giorgi and Stevenson, 1995 summarize Long, 1968; Magne, et al., 1983; 

Steig and Johnson, 1986; and Johnson, et al., 1987). Observations in the mid-Columbia 

generally agree with the summary of Giorgi and Stevenson, although occasional 

differences raise questions regarding the possibility of differences for sockeye and 

perhaps coho. (Findings of the mid-Columbia Coordinating Committee annually for the 

years 1980-1993.) 

Further evidence of the surface orientation of juvenile salmon comes from the fact 

that juveniles are observed to accumulate in gatewells of unscreened turbine intakes, as 

first noted in the early 1960’s by Cliff Long and George Snyder (Mighetto and Ebel, 

1995). In addition, juveniles generally sound to significant depths only when no 

alternative is presented (Wagner and Ingram, 1973; Dunn, 1978). Numerous 

hydroacoustic studies that were undertaken at each of the five mid-Columbia projects 

showed that juvenile salmon were concentrated in the upper portion of the water column, 

generally in the upper one-third. (Biosonics, numerous - see references. e.g. Ransom, et 

al. (1988) found that fish approaching Rock Island Dam were surface oriented.) Juvenile 

salmon have been sampled in the Wells forebay with purse seines, a fishing method that 

operates at the surface (Findings of the mid-Columbia Coordinating Committee, 1989). 

15 
In the forebay at lower Granite Dam, 92 percent of the juvenile salmon were found to be 

in the upper 36 feet of the water column (Smith, 1976). The turbine intake screen 

technology depends upon the fact that juvenile salmon are concentrated near the ceiling 

of the intake as they pass through. Numerous examples exist (e.g. Long, 1968). Fyke net 

sampling at each of the mid-Columbia projects showed that 75-80 percent of the juvenile 

salmon were in the upper portion of the intakes (e.g. Hays, 1984). 

Eicher (1988) reviewed studies of passage efficiency at deep intakes. The studies 

of Regenthal and Rees (1957) were particularly informative. They showed 55 percent of 

chinook would exit the reservoir when the only route was 118 feet deep or less, 48 

percent when it was at 146 feet, and 8 percent when it was 160 feet (as summarized in 

Eicher, 1988). Eicher concluded that “.... it has been accepted that fish [salmonids] 

sound to great depths as a last resort, and if an alternative, such as an artificial outlet, is 

available, they will use it preferentially and can be collected in that way.” (Eicher, 

1988). 

SPILL AS A MEANS OF BYPASS FOR JUVENILE SALMON 

Normal Spill 

Depending upon the hydraulic capacity of the individual projects and the river 

flow in the particular year, there will normally be spill during the spring freshet when the 

largest numbers of juvenile salmon are moving downstream. 

Studies of mortality in spill have been conducted at six projects, resulting in 13 

estimates, Table 4. Five of the thirteen separate estimates were of zero mortality in spill. 

Five others were of 2 percent or less. Studies revealed a potential for added mortality 

from predation below the spillway.3

 One unusually high estimate of 27.5 percent at 

Lower Granite Dam was probably associated either with high predation by squawfish or 

other adverse conditions below the dam, such as were described for Little Goose Dam in 

1994 (Muir, et al., 1995A). 

Spillway design affects the rate of injury and survival, with free-fall being the 

least injurious (Bell and DeLacy, 1972; Stone and Webster, 1986). Back-roll may be 

created with certain designs and spill levels, which can trap fish in turbulence, adding to 

the potential for predation and other causes of mortality (Stone and Webster, 1986) 

Sims and Ossiander (1981) reported that spill increased survival more than flow 

did. Their analysis suggested that the first 10 percent of spill increased survival by 28 

percent, while the first 10 percent increase in flow added 13 percent survival. 

 

3

 Some references state that mortality of juvenile salmon in spill ranges from 0 to 4 percent (Fish Passage

Center, 1994), or 0 to 3 percent (NMFS/NOAA Proposed Recovery Plan, 1995). However, close scrutiny

of the studies upon which these numbers are based leads us to conclude that 0 to 2 percent is the more 

likely range for standard spill bays. In addition, local conditions such as back eddies or other situations 

that may favor the presence of predators may lead to higher numbers (e.g. such as those Muir, et al. (1995) 

suggested may have occurred below Little Goose Dam in 1994.) 

16 
Table 4. Estimates of Mortality of Juvenile Salmon and Steelhead in spill. 

Mortality Species Location Reference  2% chinook McNary Dam Schoenem

an, et al. (1961) 

 2.2% steelhead Lower Monumental Dam Long, et al. (1975) [For spill bays wi

 27.5%* steelhead Lower Monumental Dam Long, et al. (1975) [For spill bays wi 4%** chinook Lower Monumental Dam Muir, et al. (1995B) [For combined b 1.5% chinook Lower Monumental Dam Muir, et al. (1995B) [For spill bay wi 7% chinook Lower Monumental Dam Muir, et al. (1995B) [For spill bay wi

 0%*** steelhead 

W

ells Dam

W

eitkamp, et al. (1980) [Confidence 

 1% coho Rocky Reach Dam Heinle and Olson (1981)  0% chinook Bonneville Dam Ledgerwood, et al. (1990)  0% chinook Bonneville Dam Johnsen and Dawley (1974) [For spill  0% chinook Bonneville Dam Johnsen and Dawley (1974) [For bay  1% chinook John Day Dam Raymond and Sims (1980) [Authors c point estimate did not differ from 0]  0% chinook Little Goose Dam Iwamoto, et al. (1994) * This unusually high estimate at Lower Granite Dam was probably associated either with high predation by squadverse conditions below the dam, such as were described for Little Goose Dam in 1994 (Muir, et al. 1995A). S** Muir, et al. (1995B) found no statistically significant difference between the survival estimates for spill bays deflectors, in spite of what the point estimates might suggest. *** The mid-Columbia Coordinating Com

mittee agreed that the estimate was zero (mid-Columbia Coordinating 

17 
Spill Deflectors – Perforated Bulkheads and “Flip-Lip” 

Spillways 

A problem encountered with high spill amounts is gas supersaturation, leading to 

a condition in fish similar to the divers “bends”, in which gas bubbles appear in the blood 

stream and other tissues, which can lead to death (Ebel, 1969; Ebel, et al., 1975; Bouck, 

1980). The subject is discussed in more detail in Return to the River (ISAB 96-6). The 

condition of supersaturation is brought about by the plunging of water from the spillway, 

carrying air with it and putting it under pressure in the pool below. As the pressure is 

removed, the bubbles appear. 

Perforated Bulkheads in Turbine Intakes 

In an effort to reduce nitrogen supersaturation, slotted bulkheads were installed by 

the Corps in 27 of the empty turbine bays in the lower Snake River projects in 1971 

(Long, et al., 1972). Prototype tests at Little Goose Dam had shown that water could be 

run through the slotted bulkheads with little increase in nitrogen saturation. However, 

the mortality rate of smolts passing through the slotted bulkheads was measured at 50 

percent at Lower Monumental Dam, which led to their abandonment (Long, et al., 1972). 

Spill Deflector - "Flip Lip" Spillway Design 

A remedy that has been adopted is a spill deflector (“flip lip”) design for the 

spillway, which directs the spill in a horizontal direction, rather than vertical (Smith, 

H.A. Jr., 1974). At flows of 123 to 169 kcfs, the spill deflectors at Little Goose Dam

were shown to reduce gas saturation levels downstream by about 10 percent, relative to 

levels before the deflectors were installed. Saturation was measured at 128 percent with 

spill of 46 to 59 percent of flow (Park, et al., 1977). At Lower Monumental and Lower 

Granite dams, also equipped with spill deflectors, they found gas saturation levels to be 2 

to 8 percent lower than at Little Goose, under the same flow conditions. These lower 

levels were probably due to the greater depth of the stilling basin below Little Goose 

Dam and smaller deflectors there, 8 feet in length compared to 12 feet at the others. At 

McNary Dam, they found gas saturation was lower by 16 to 20 percent with the spill 

deflectors in place than it had been before (Park, et al. 1977). 

In a more thorough analysis, Johnsen and Dawley (1974) developed curves 

showing the relationship of gas saturation levels below the spillway with forebay gas 

levels, spill discharges, water temperatures, tailwater elevations and effects of deflectors 

at Bonneville Dam. With forebay gas levels of 110 percent and tailrace elevations of 24 

feet, the deflectors generally reduced gas saturation levels by about 10 percent (130 

percent reduced to 120 percent). But at higher discharge rates (thus tailrace elevations) 

the difference lessened, to the extent that it appeared the deflectors might be 

disadvantageous at spill discharges above 14 kcfs per bay. 

18 
Implementation of Flip-lip Spillway Design 

The demonstrated success of spill deflectors in reducing levels of gas saturation 

has led to installation of these devices at several Corps dams, and a call by NMFS/NOAA 

for improved devices at Ice Harbor and John Day dams. Additional information on 

installation at specific projects is provided in Appendix A. Only Lower Granite Dam is 

fully equipped with flip-lip spillbays across the spillway. Four of the eight Corps 

projects in the Snake River and lower Columbia River, namely Little Goose, Lower 

Monumental, McNary and Bonneville dams are partially equipped with spill deflectors. 

They are being planned for installation at Ice Harbor in 1997 and John Day in1998 

(NMFS/NOAA, 1995; Bruce, 1995; Fishery Agencies and Tribes, 1993). (See Appendix 

A.) 

Effectiveness of Spill 

In evaluating the effectiveness of various passage routes for juvenile salmon 

migrating downstream, reference to Figure 2 is useful for explaining several terms that 

will appear later in the text. Fish passage efficiency (FPE), or simply fish passage, is the 

percentage of total fish approaching a project that are passed by routes other than the 

turbines. Fish guidance efficiency (fish guidance efficiency) is the percentage of fish 

approaching a turbine intake that are successfully diverted, usually by screens, into a 

bypass system. Similarly, spill effectiveness and effectiveness of the ice and trash 

sluiceways are evaluated in terms of the percentages of total fish that are diverted into 

spill or the sluiceways. Thus, fish passage efficiency is the total of fish guidance 

efficiency added to spill effectiveness and effectiveness of the ice and trash sluiceways. 

In other words, fish passage, as the term is used, includes all the fish except those that 

continue their passage through the turbines. In each route, there may be associated injury 

or mortality of fish. An additional standard of fish survival is therefore applied to those 

fish that are successfully passed away from the turbines by each route, i.e. survival in the 

bypass system, survival in spill, and survival in the ice and trash sluiceway. 

In the 1980's, studies of spill effectiveness were done that used hydroacoustic 

technology at each of the mid-Columbia projects. These studies revealed that the 

relationship between the percentage of juvenile salmon passed in spill and the spill 

volume relative to total river flow is complex and varies from project to project 

(Raemhild, et al. 1984; Biosonics, 1983A; Biosonics 1983D; Biosonics 1984). For the 

studies, spill percentage relative to river flow was maintained for a week at each of four 

levels: 20, 40, 60 and 80 percent (85 percent at one project). Curves were developed that 

described the relationship for each project. As an example of the non-linear relationship 

often found, at Wanapum Dam in the spring of 1983, night-time spill of 20 percent of the 

instantaneous flow passed on the average about 45 percent of the fish, while spill of 50 

percent passed 60 percent of the fish (Biosonics, 1983 D). On the other hand, at Rocky 

Reach Dam during the spring of 1983, night-time spill that amounted to 20 percent of the 

instantaneous river flow was estimated to pass about 16 percent of the fish. Spill of 50 

19 
percent passed about 30 percent of the fish, and spill of 80 percent passed about 55 

percent of the fish (Biosonics, 1984). 

Experience in 1995 at Priest Rapids and Wanapum Dams showed that spreading 

the spill of a given total volume of water (a certain number of acre feet) over a 24 hour 

period doubled the percentage of fish passed in spill, as compared to spilling the same

volume over a 12 hour period at night. These two situations might have been expected 

to pass the same percentage of fish or less, given the volume for volume comparison. In 

fact, at Priest Rapids Dam in 1995, 17 percent spill for 24 hours for 60 days during the 

summer achieved 62 percent fish passage. Whereas in the summer of 1994, spill of 40 

percent for 12 hours per night for 34 nights only achieved an estimated 33 percent fish 

passage (Hammond, 1995). 

As for the Corps projects, in the late 1970’s NMFS/NOAA investigators were 

seeking ways to increase the passage rate of juvenile salmon over the spillways (Giorgi 

and Stevenson, 1995). Spill effectiveness has been studied, using hydroacoustic 

technology, at John Day Dam annually since 1983 (Magne, et al., 1987A, 1987B; Kuehl, 

1986; Johnson and Wright, 1987; McFadden and Hedgepeth, 1990; Ouellete, 1988; all as 

summarized by Giorgi and Stevenson, 1995). Magne, et al. (1987) focused on 

developing an overall ratio of percentage fish passage to percentage spill for a range of

values from 37 to 66 percent spill, for the spring and summer seasons. They found spill 

effectiveness ratios of 1.3 in 1987, 1.4 in 1989, and 1.1 in summer, 1988. Analysis of the 

spring observations is hampered by a paucity of observations at spill levels other than 

around 50 percent. Only three observations were below 45 percent spill (four counting 

the intercept). This leads to caution in drawing inferences. Although our analysis 

suggests there is a difference between spring and summer, we believe it best to combine 

the data for both seasons until a wider range of spill values may be available. The 

relationship then falls short of 1.0. The combined data would estimate 50 percent fish 

passage in 60 percent spill at John Day Dam. Obviously, spill effectiveness must 

improve at some spill level beyond the observations, since 100 percent spill must include 

100 percent of the fish. 

Willis (1982), using marked coho, estimated effectiveness of the ice and trash 

sluiceway at The Dalles Dam in passing fish at various levels of spill from about 10 

percent to about 60 percent of the river flow. He was able, using equations developed 

from regression analysis of the data, to calculate the percentage of fish that must pass 

through spill at given flow levels. These calculations revealed spill effectiveness 

estimates of about 30 percent fish passage at 10 percent spill, and 75 percent fish passage 

at 40 percent spill (Willis, 1982). This high effectiveness of spill and of the ice and trash 

sluiceway is not surprising, considering the configuration of The Dalles Dam. The dam's 

spillway is at right angles to the natural course of the river, the powerhouse is nearly 

parallel to the natural course of the river, and the sluiceway is at the downstream end of 

the powerhouse. (See Giorgi and Stevenson, 1995, Figure 11.) 

Surface Spill 

On the basis of a study at John Day Dam, Raymond and Sims (1980) suggested 

that surface spill would be more effective in passing fish than standard spill. The 

standard spill gates in the Columbia River projects are designed to open from the bottom

20 
of the spillbay, typically at depths near 50 feet; (47-58 feet below normal operating pool 

at John Day Dam, for example, according to Giorgi and Stevenson, (1995)). Raymond 

and Sims placed stop logs in the spillbay to create surface spill. They found that juvenile 

salmon passing through the bays with surface spill were as likely to pass in the day as at 

night. In comparison, samples of juvenile salmon from the turbine intakes, the ceilings of 

which were located at about the same depth as the bottoms of the unlogged spill bays, 

showed a strong peak at night. This finding suggested that juvenile salmon approaching 

the dam delayed sounding to the intakes until after dark, and that they more readily 

passed through surface spill. Giorgi and Stevenson (1995) observed that surface spill 

remains to be adequately evaluated at Corps projects. The Corps has begun studies on 

effectiveness of surface spill. 

Some projects are fitted with sluiceway spill gates that open from the top. 

Wanapum and Priest Rapids dams are each equipped with one such gate that is located 

closest to the powerhouse in the array of spill gates, Figure 3. They are smaller spill 

bays, being designed for passage of debris rather than control of water elevation in the 

forebay. It was thought that spill at these sluiceways might be especially effective in 

passing juvenile salmon because of their proximity to the powerhouse, where flow is 

normally concentrated. Hydroacoustic evaluations confirmed this hypothesis, Table 5 

(Ransom and Malone, 1990; McFadden, et al., 1992, Ransom, 1995). 

_____________________________________________________________________ 

Table 5. Sluiceway (Surface Spill) Effectiveness in Passing Fish. 

Project Season % Fish Passed % River Flow Spilled Spill Duration 

Priest Rapids Spring 3.0% 1.3% 12h (night) 

1.6% 0.3% 24h 

 Summer 4% 2% 12h (night) 

 2.1% 0.6% 24h 

Spill in the sluiceway was judged to be twice as effective as spill in the spillway. 

Wanapum Dam 

 Spring 4% 0.5% 24h 

__________________________________________________________________ 

The spillway at Rock Island Dam is equipped with several gates that open from

below, but at a depth of about 35 feet, as compared to another set of gates that opens 

from a depth of about 55 feet. There, when spill was split 50:50 between deep and 

shallow spill gates, the shallow spill gates passed 87 percent of the fish passing in spill 

(Ransom, et al., 1988).

21 
Figure 3. Cross sectional diagrams of the Wanapum Dam sluiceway and spillway. The spillway diagram shows t

which opens from the bottom upward to control the flow of water. Both are equipped with such gates. (Modified Malone, 1990) 

22 
Effectiveness of Surface Spill 

Current thinking is that these sluiceways at Wanapum and Priest Rapids dams are 

more effective than the standard spill gates, not simply because they are located closest to 

the powerhouse, but because they operate in the upper portion of the water column where 

the fish prefer to be. Accordingly, Grant County Public Utility District modified a 

standard spill gate at Wanapum Dam in 1996 to evaluate surface spill. Tests will also be 

conducted in 1996 at The Dalles, and Lower Granite dams to determine whether an 

overflow weir improves passage at the spillway and to determine at what location and 

under what conditions an overflow weir will operate most efficiently at those projects. 

Implementation of Spill as a Means of Smolt Bypass 

The following discussion is an overview of spill as a measure implemented for 

passage of juvenile salmon at projects in the mainstem Columbia and Snake rivers. More 

detail is provided in Appendix A about requirements by FERC, the NPPC and 

NMFS/NOAA for spill and other bypass measures. Appendix B then provides an 

analysis of the effectiveness of the bypass measures, including spill, in achieving the 

goals for fish passage and other goals established by those agencies, using the 1995 

experience as an example. 

As a result of increased storage from river development, high flows previously 

experienced in the spring during the peak of outmigration of juvenile salmon were 

reduced in the late 1970's. This decreased spill, which forced a higher percentage of the 

fish to pass through the turbines. One early consequence was a complaint filed before the 

FERC in 1976 by the State of Washington Department of Fisheries, later joined by the 

Oregon Department of Fish and Wildlife, certain Columbia River Treaty Tribes, and the 

United States National Marine Fisheries Service against the three mid-Columbia Public 

Utility Districts. A contributing factor to the complaint was a low flow of 36 kcfs

between April 9-11, 1996. The Washington Public Power Supply System requested this 

flow to test water intake structures at Hanford (Carlson and Dell, 1989). This low flow 

caused a kill of chinook in the Hanford Reach. The complaint requested provision of 

minimum flows for fish at the five projects operated by the public utility district’s in the 

mid-Columbia reach, (FERC mid-Columbia Proceeding, Docket # E-9569). 

The primary objective of the petition was to stabilize flows for spawning fall 

chinook in the Hanford Reach below Priest Rapids Dam, and especially to establish 

minimum flows to prevent exposure of redds. The result was a more far-reaching 

settlement agreement that the parties reached in October 1979. This agreement consisted 

of two parts. One, the Vernita Settlement Agreement called for a four-year study of 

chinook spawning at Vernita Bar. Two, the mid-Columbia Settlement Agreement 

provided for studies over a five-year period to find ways to measure the effects of the 

projects on the downstream migration of juvenile salmonids in the mid-Columbia reach 

and to find ways to improve production of salmonids (Settlement Agreement of 1979, 

FERC Docket No. E-9569). As an interim measure, the agreement provided for spill of 

10 percent of the river flow at each of the projects during the period in the spring when 

23 
the middle 80 percent of the migrating juvenile salmon were determined to be present. 

This spill program, which began in the spring of 1980, was the first formal application of 

spill as a bypass measure for juvenile salmon in the Columbia Basin. Spill continues to 

be the primary method for bypass of juvenile salmon at four of the mid-Columbia 

projects. Wells Dam, the fifth dam and the one exception, is equipped with a mechanical 

bypass system, which will be described below. 

In 1994, the FERC ordered Grant County Public Utility District to provide 

sufficient spill at Wanapum and Priest Rapids dams to pass 70 percent of outmigrating 

juvenile salmon during 80 percent of the migration in the spring and 50 percent during 80 

percent of the migration in the summer (FERC Docket No. E-9569-003, Grant County 

Phase. Order of May 24, 1994). Those spill levels are to be interim measures pending 

installation of mechanical bypass systems or a contrary order of the Commission. 

Production of gas supersaturation by these spill amounts has prevented full 

implementation of the order. Consequently, spill of 17 percent was provided in spring 

and 14 percent in summer in 1994. These amounts provided passage for an estimated 50 

percent of the fish in spring and 25 percent in summer at Wanapum Dam in 1994, while 

at Priest Rapids Dam 50 percent were passed in the spring and 62 percent in the summer 

(Hammond, 1994). More details are provided in Appendix B. 

In 1989, pursuant to a measure in the NPPC’s Fish and Wildlife Program of 1984, 

the fishery agencies, tribes, and BPA reached a memorandum of agreement on spill at 

federal projects. This agreement established the amount of spill to be used in spring and 

summer as an interim measure at Lower Monumental, Ice Harbor, The Dalles, and John 

Day dams, pending the development of solutions to fish passage problems (FPC, 1990). 

However, this agreement has been superseded by requirements of the NMFS/NOAA 

Biological Opinion for endangered Snake River salmon, which requires a standard of 80 

percent fish passage during time periods set for spring and summer migrants 

(NMFS/NOAA, 1995B). At the Corps projects, implementation of this standard is 

complicated, because the bypass facilities’ effectiveness in providing fish passage varies. 

This variation depends on a number of factors, but is less than the 80 percent standard for 

some species at all projects and for all species at some projects. Spill amounts are to be 

provided to make up the difference up to the 80 percent passage standard. More 

information on this subject appears below and in Appendix B, which is an analysis of 

attempts to achieve the goals in practice during 1995. 

MECHANICAL BYPASS SYSTEMS 

Introduction 

Early studies of mortality in turbines stimulated studies of juvenile salmon 

behavior. Biologists sought to find a clue that might lead to directing juveniles away 

from the intakes (Summarized to 1960 by Andrew and Geen, 1960: Examples are Brett 

and MacKinnon, 1953; Brett, 1957; Brett and Alderdice, 1958; also Collins and Elling, 

1964). They investigated batteries of lights, bubble curtains, electric fields, and sound, 

among other things. None of these methods was found to be sufficiently effective in 

directing fish movements to justify full-scale or prototype field testing for application at 

24 
large hydroelectric projects (Ebel, 1981; Mighetto and Ebel, 1995; Office of Technology 

Assessment, 1995). More information on these is provided below. 

Improved Turbine Efficiency

The studies summarized above show higher fish passage survival when turbine 

efficiency is higher. In addition, damage to machinery is minimized at high efficiencies. 

These two factors provide incentives to operate the machines in the region of their 

highest efficiency. Furthermore, improvements have been made in the design of turbines 

to increase their efficiency, and these have been fitted at a number of projects as 

replacement is required. One example is Wells Dam where installation began in 1987 

and was completed in 1990 (personal communication Ken Pflueger, Douglas County 

Public Utility District). At Rocky Reach Dam, planning for installation of such improved 

turbines began in 1993, and is under way in 1995 with a schedule for completion in the 

year 2001 (personal communication Bill Christman, Chelan County Public Utility 

District). At Rocky Reach Dam the schedule for installation of new runners was 

expedited and improvements were included that incorporated designs based on studies of 

juvenile salmon mortality in the turbines. The studies indicated such changes might 

improve fish survival by 1.7 percent)(RMC Environmental Services and Skalski, 1993). 

Ledgerwood, et al. (1994) measured mortality of juvenile salmon that passed through 

turbines at Bonneville’s second powerhouse. Their mortality estimates of 2.3 percent 

were lower than most elsewhere (Ledgerwood, et al., 1993). They suggested that the 

lower estimates were due to higher efficiency of the turbines at that project and a deeper 

submergence of the blades. However, their conclusion needs to be considered in the 

context of our previous discussion indicating that many of the estimates of mortality in 

turbines include mortality that occurs in the tailrace or below. The Corps is working to 

develop an advanced turbine design aimed at improving efficiency and reducing smolt 

mortality (Office of Technology Assessment, 1995). 

Turbine Intake as a Passage Route 

Free wheeling, or locking of the runners of turbines was investigated at Rocky 

Reach Dam as a possible means of passing juvenile fish without harm (Stone and 

Webster, 1982). It was concluded that this would not prevent pressure changes in the 

scroll case, which would lead to cavitation and injuries caused by fish strikes in transit. 

Division Barriers Upstream of the Powerhouse 

Prior to the construction of Hells Canyon Dam in 1967 and following 

construction of Brownlee Dam in 1958, it was found that juvenile salmon experienced 

great difficulty in passing through the reservoir above Brownlee Dam (Graban, 1964; 

Haas, 1965). As a consequence of the high storage volume relative to inflow and 

outflow, water velocities were judged to be too low to stimulate movement of the 

juvenile salmon. An additional difficulty was that the turbine intakes were located at 

depths of over 200 feet, too deep for surface oriented juvenile salmon to readily use for 

passage. This difficulty was well documented elsewhere, as noted by Eicher (1988). A 

25 
barrier net was placed in the reservoir above Brownlee Dam. The net extended completely across the river at a point 4800 feet upstream of the dam and reached to a depth of 120 

feet. The barrier was equipped with a walkway to provide access to three inclined-plane 

fish traps located at the surface along its length. Each of the traps was equipped with a 

pump to provide appropriate flow to attract juvenile salmon. (See "gulpers" described 

below.) The equipment was difficult to keep in place because of adverse weather and 

accumulation of debris. Furthermore, efficiency of the net in guiding fish was poor as 

fish passed through or under it. The idea was abandoned (Mighetto and Ebel, 1995). 

The problem became moot when Hells Canyon Dam was built in 1967 and provisions for 

adult passage there failed (Petersen, 1995). 

At Wanapum Dam, a barrier net 12,000 feet long and 40 feet deep was tested. 

The net extended laterally from a point on the left bank upstream of the powerhouse 

across the powerhouse to a point 800 feet west of the powerhouse, leading toward the 

spillway. In this case, the intention was to lead fish away from the turbine intakes toward 

the spillway (Tyler and Pock, 1989). However, many problems had to be overcome. 

Strong currents required heavy anchoring systems. Accumulation of debris required 

deployment of the net with its cork line below the surface. Regular cleaning was needed 

because of accumulation of periphyton. In addition, the net only briefly affected 

migration of juvenile salmon that encountered it. After three years, further testing was 

abandoned when it was concluded that the net was not effective at diverting juvenile 

salmon away from the powerhouse. 

In 1989, a "forebay wedge screen" was tested at Priest Rapids Dam (Ransom and 

Malone, 1989). It consisted of a wedge wire barrier mounted on a framework in the 

forebay in front of turbine unit 9. Although it diverted some juvenile salmon, counts of 

fish in the gatewells were about 10 percent of those in adjacent gatewells, the frame was 

difficult to handle, and periphyton accumulation led to unacceptable head loss. Further 

tests were abandoned. 

Fish “Gulpers” 

While the barrier net concept has used nets stretched across the migration path, a 

related concept has been employed, based on the idea that migrating fish could be 

attracted or directed to a collection device without completely blocking their path. In 

some of these, pumps were used to create attraction flows for outmigrants that brought 

the fish into an enclosure of some kind (e.g. “Merwin” Trap). Such devices were tested 

at Pelton Dam on the Deschutes River, Mud Mountain Dam, and Merwin Dam on the 

Lewis River (Stockley, 1959; see DeHart, 1987). A device with much higher attraction 

flows was used with some success at Green Peter Dam on the Middle Fork Santiam

River, Oregon, where the device is built into the upstream face of the dam (Wagner and 

Ingram, 1973). At Baker Lake, Washington, a surface collection device of this type was 

found to be effective at collecting sockeye juvenile salmon for transportation below the 

powerhouse (Wayne, 1961; Quistorff, 1966). It became a viable solution to the problem

of collecting juvenile salmon in the reservoir when a lead net was added to the “gulper” 

(Cary Feldmann, Puget Sound Power and Light, personal communication). 

26 
Gatewell Salvage 

It was early observed that juvenile salmon accumulate in turbine intake gatewell 

slots, a result of their tendency to pass through the intakes near the ceiling (First observed 

by C.W. Long, and G. Schneider, according to Mighetto and Ebel, 1995). Bentley and 

Raymond (1969) describe the use of a dip basket for salvage of juvenile salmonids from

gatewells at dams in the Columbia River. 

A fish salvage operation was undertaken at John Day Dam in 1977, in 

anticipation of low flows that were expected to lead to accumulation of fish in the 

gatewells (Johnsen, 1978). The numbers removed from the gatewells were 

disappointingly low, about 21,000 juvenile salmonids, mostly chinook yearlings. 

On the other hand, marked juveniles that were released in the Wanapum reservoir 

were recovered downstream in the gatewells at Priest Rapids Dam at the rate of 5 percent 

for coho, 2.1 percent for chinook yearlings and 3.6 percent for steelhead (CH2M Hill and 

Wash. Dept. Fish., 1980). During the initial five years of the mid-Columbia Settlement 

Agreement, the gatewells at Wanapum and Priest Rapids dams were emptied regularly 

and enumerated to obtain an index of fish passage. Following the Stipulation of 1985, 

Grant County Public Utility District has salvaged fish from the gatewells at Wanapum

and Priest Rapids dams on a daily basis during the outmigration, weather permitting. 

Specially designed nets deployed by mobile cranes from the deck of the powerhouse are 

used to remove fish that have accumulated. Captured fish are placed into tank trucks and 

transported to below the dam where they are released into the tailrace. In the 

neighborhood of 150,000 to 200,000 fish are salvaged at each of the two projects each 

year in the spring and an additional 30,000 to 50,000 in the summer (personal 

communication Stuart Hammond, Grant County Public Utility District No.2). 

Airlift 

 

A gatewell airlift system was tested at McNary Dam in 1981. This test was part 

of a study of a proposed intake screen configuration at John Day Dam. While the airlift 

did not affect the guidance of fish, the turbulence it created in the gatewell made it 

difficult for the fish to exit through the orifices which led to unacceptably low orifice 

passage efficiency (Swan, et al., 1982; Krcma, et al. 1983). An airlift installed at John 

Day Dam is now used to sample fish diverted into the gatewell by intake screens (Brege, 

et al., 1990; Wood, 1993). 

At Rocky Reach Dam, in 1980, an airlift was investigated as a means of drawing 

fish out of the gatewells. It was concluded that the airlift was not effective in drawing a 

significant number of fish up the gatewell, although it could be used to remove some fish 

from the gatewell (CH2M Hill, 1982). 

Gatewell Conduit 

When the second powerhouse at Rock Island Dam went into service in 1979 it 

included, as a provision for juvenile fish passage, orifices between the gatewells and a 

27 
conduit leading from there to the tailrace. It also included a feature allowing for 

diversion of a portion of the fish thus collected, into a sampling facility (Olson, 1981, 

1982). The effectiveness of the system in diverting fish from the turbine intakes was 

found to vary among species and from year to year. Effectiveness depended upon levels 

of spill relative to river flow, and ranged around 5 to 15 percent. Effectiveness was 

higher in years with low spill, as might be expected. 

Other 

The Office of Technology Assessment (1995) refers to these as “Alternative 

Behavioral Guidance Devices.” They concluded that for the most part, these devices 

have not been accepted by the resource agencies because they have not been shown to 

divert a high enough percentage of the fish (Office of Technology Assessment, 1995 p. 

87). Stone and Webster (1987) concluded that, up to the time of their review for EPRI, 

such devices had not offered much promise of meeting agency goals. 

Nevertheless, from time to time, there is a revival of interest in these methods. 

Investigators either have a new perspective on the method (e.g. Carlson, 1995) or are 

unaware that it has been tried. Some of these methods have met with varying degrees of 

success for other species in different applications, such as at pump intake diversions or 

irrigation diversions (Office of Technology Assessment, 1995). 

As mentioned previously, in the 1950s and 1960s the Fish Passage Program of the 

then Bureau of Commercial Fisheries (now NMFS/NOAA), under the direction of Gerald 

B. Collins, investigated a number of potential methods for their efficacy in directing 

movements of fish. These methods included banks of lights, bubble curtains, sound, and 

electric fields, none of which proved to be practical for application in the field (Mighetto 

and Ebel, 1995). Andrew and Geen (1960) reviewed the studies beyond those of the 

Bureau of Commercial Fisheries and came to the same conclusion. Some other pertinent 

studies are summarized below. 

Electric Fields 

Effectiveness of electrical barriers at power plant intakes has been generally poor 

(Stone and Webster, 1987). Collins and his colleagues found that successful application 

of this technology would be limited to situations where velocity of flow was less than 1 

fps (summarized by Mighetto and Ebel, 1995). This would represent a serious limitation 

at the turbine intakes in the Columbia Basin. For example, Odgaard, et al. (1990) 

determined that the approach velocity measured immediately upstream from the intake 

screen at Wanapum and Priest Rapids dams was on the order of 1.1-1.2 m/s. (3.6-3.9 fps). 

There are other serious drawbacks with the application of electricity. Electric fields are 

potentially dangerous to other fish that may be present. Susceptibility to dangerous 

shock is a function of fish size. Adult fish are more vulnerable than juveniles (Office of 

Technology Assessment, 1995). 

 

Sound 

28 
Recently, Carlson (1994) reviewed the extensive literature base regarding studies 

that have been conducted to direct fish by means of sound. He concluded that sound 

deterrence for salmonids is possible only at short ranges using very low frequencies. 

Significant challenges remain in the possible application of sound to address problems of 

systems intended to modify fish behavior. Dolat, et al. (1995) reported success in using 

sound to divert a portion of the juvenile salmon that approached the intake of an 

irrigation diversion at Dryden Dam on the Wenatchee River. Although a clear effect of 

sound was established, it was not as effective as the screen that is in place (Mueller, et 

al., 1995). 

Light 

Mighetto and Ebel (1995) report that Paul Fields was able, using lights, to divert 

juvenile salmon away from the turbine intakes and toward the spillway, but was unable to 

sustain that response over a 24 hour period. Fields (e.g. 1966) developed a large body of 

information on the effects of light on migration of salmonids, most of which fits the 

summary in the previous sentence. 

In 1986, strobe lights mounted on the trash racks in the turbine intakes were 

investigated at Rocky Reach Dam as a possible means of guiding fish away from the 

intakes, (Hays and Truscott, 1986). Although the lights affected the vertical distribution 

of juvenile salmon entering the gatewell, it was concluded that there was no way to use 

them effectively to assist fish in avoiding the intake. Mercury vapor lights attached to the 

frame of a guidance device at Bonneville Dam in tests over several years did not 

significantly increase guidance or decrease descaling of subyearling chinook (Gessel,, et 

al., 1990). 

Louvers 

 

Angled louvers have been used effectively at pump intakes and irrigation 

diversions to divert juvenile salmon and other small fish into alternate channels (Stone 

and Webster, 1986; Office of Technology Assessment, 1995). Louvers have been widely 

applied in the Sacramento River system as fish protection devices (Stone and Webster, 

1986). They are considered to be standard technologies for turbine intakes in the 

Northeast but not in the Northwest (Office of Technology Assessment, 1995). The 

difference is apparently due to the high water volumes and velocities present in 

Northwest river applications. In the Columbia Basin, the primary application has been at 

irrigation diversions in conjunction with screens. Collins' group found that louvers 

would only be effective in diverting a high enough percentage of juvenile salmon in 

situations where flows were carefully regulated at low levels and floating debris was 

sparse (summarized in Mighetto and Ebel, 1995). At Sullivan Dam on the Willamette 

River, louvers, made of modified trash racks, guide fish from intakes at units 1 through 

12 into the intake for unit 13 where an inclined screen diverts them away from the 

turbines (Stone and Webster, 1986). Best estimates of effectiveness ranged from about 

40 percent for subyearling chinook to 80 percent for yearling chinook approaching the 

project (Clark and Cramer, 1977, as cited in Stone and Webster, 1986). 

29 
Vertical louvers were located behind each screen panel at the Dryden 

Reclamation District Canal on the Wenatchee River. This was done to facilitate the 

workings of the screens and to balance the flow across the set of screen panels. This 

effort was not completely successful in balancing the flow (Mueller, et al., 1995). 

Turbine Intake Screens 

Submerged Traveling Screens (STS) 

In the early 1960’s, studies by Bureau of Commercial Fisheries investigators 

showed that juvenile salmon tended to be concentrated near the ceiling of the turbine 

intakes, and a portion of them were drawn above into the gatewells (Long, 1968). This 

led to the idea that fish might be screened or deflected from the upper portion of the 

intake, with minimal effect on the generating capacity of the unit. The concept was first 

tested at model facilities at Washington State University. These initial studies, conducted 

under the aegis of the Bureau of Commercial Fisheries, also identified optimum screen 

porosities and deflection angles to minimize impingement of fish on the screen. The 

model studies led to predictions of a unit head loss of less than 10 percent resulting from

placement of the screen at the intake, which was deemed acceptable. A cleaning 

mechanism was recommended in order to avoid violation of the operating criteria 

(Mueller and Osborn, 1969). The first test of a prototype device in the field took place in 

1969 and 1970 at Ice Harbor Dam on the lower Snake River (Long, et al., 1970). The 

first design incorporated a traveling screen as a self-cleaning feature. Consequently, the 

device was named the submerged traveling screen (STS). Mighetto and Ebel (1995) 

summarized the decades of work by the Bureau (later NMFS/NOAA) and the Corps to 

develop a satisfactory intake screen, Figure 4. 

30 
Figure 4. Cross sectional diagram showing the locations of the turbine intake screen, a 

bank of fyke nets behind the screen and across the entrance to the turbine intake to 

capture fish not guided, and the gatewell area above the screen. Guided fish are restrained 

from other exits to the gatewell by the vertical barrier screen. Fish may exit the gatewell 

by way of a submerged orifice into the juvenile bypass flume. Diagram of configuration 

used at Little Goose Dam to measure FGE of prototype intake screens. Fyke nets are not 

present in completed installations. (Source: Gessel et al, 1995.) 

31 
The first screen tested in prototype was approximately 24 feet in length, which 

corresponded with dimensions in the model, and could be deployed at angles of 45 to 60 

degrees (Marquett, et al., 1970). It was tested at Ice Harbor Dam in 1969 and 1970. 

These tests showed that by using the screen the relative number of juvenile salmon in the 

gatewell could be increased by a factor of three. Later, to refine an estimate of the fish 

guidance efficiency of the screen, i.e. the percentage of fish entering the turbine intake 

that are guided by the screen, an array of fyke nets was placed below the screen in the 

intake to capture fish not guided by the screens. Guided fish were removed from the 

gatewell and counted, which made it possible to estimate fish guidance efficiency. Over 

the next several years, devices were also tested at Little Goose and Lower Granite dams, 

and improvements were made in the design. Details are to be found in Ebel, et al. (1974) 

and Park, et al. (1977). Addition of a porosity plate behind the screen reduced 

impingement of fish to acceptable levels. Perforated steel panels, referred to as a vertical 

barrier screen (VBS), split the gatewell. These panels distributed the flow upward and 

discouraged fish from sounding out of the gatewell and back into the intake. 

Fixed Bar Screens 

In the mid-1970s planning for addition of a second powerhouse at Bonneville 

Dam led to testing of an intake screen at that project (Ruehle, et al., 1978). Experience 

with the traveling screens showed that they were costly to build and maintain. These 

Bonneville intake screen tests used a fixed screen concept that would be less complex 

and less costly. It was five feet wide and extended across the full width of one intake 

slot. Results were promising and led to testing of a full-scale device at McNary Dam in 

1978 that had somewhat different features (Krcma, et al., 1978). Rather than flat steel 

bars used in the test at Bonneville, the McNary test used smooth steel bars, triangular in 

cross section (wedge wire). Cleaning could be accomplished by periodically raising the 

angle of the screen to create a backflush through the mesh. Results were favorable 

(Ruehle, et al., 1978; Krcma, et al., 1980). Tests of a bar screen design in prototype at 

Priest Rapids and Wanapum dams later confirmed the favorable results of the 

NMFS/NOAA test of the bar screen design at Bonneville and McNary dams (midColumbia Coordinating Committee, 1988). On the other hand, problems with 

accumulation of trash in tests of bar screens at the Bonneville second powerhouse led to a 

recommendation initially to proceed with traveling screens there and at other Corps 

projects (Gessel, et al., 1991). 

Extended-length Screens 

Initial tests in 1983 of a submerged traveling screen at Bonneville Dam’s second 

powerhouse showed surprisingly poor effectiveness in guiding fish, with fish guidance 

efficiency less than 25 percent for chinook and coho. It was also observed that 

effectiveness of the intake screens at the first powerhouse had declined substantially 

since tests in 1981, from about 75 percent for yearling and subyearling chinook to about 

20 percent in 1983 (Krcma, et al., 1982; Krcma, et al., 1994). The probable cause was 

modification of the navigation lock during construction of the second powerhouse, which 

32 
involved removal of part of Bradford Island (Gessel, et al., 1991). Efforts were thus 

directed at improving fish guidance (Gessel, et al., 1992). In 1994, a frame with bar 

screen was attached to the trash rack in a position where it would simulate an extension 

of the submerged traveling screen - an extended screen. Fish guidance efficiency was 

improved. 

Similarly, at Lower Granite Dam, initial tests in 1982 of the submerged traveling 

screen indicated poor effectiveness (about 50 percent) in guiding yearling chinook. From

1984 to 1989, NMFS investigators sought ways to increase fish guidance efficiency 

(Swan, et al., 1992). A fixed bar screen was tested in conjunction with a standard 

submerged traveling screen in a configuration that simulated an extended screen, 40 feet 

in length compared to the standard screen of 24 feet. With extended screens, significant 

increases in fish guidance efficiency were measured, 66 percent for yearling chinook 

compared to 57 percent with the standard submerged traveling screen, and 83 percent for 

steelhead compared to 77 percent with a standard submerged traveling screen (Swan, et 

al., 1990). See Table 6. 

Encouraging results at Lower Granite Dam led to the design of two types of 

prototype extended-length screens, a bar screen and a submerged traveling screen that 

were tested at McNary Dam from 1991 to 1994. The results of the simulated extended 

screen tests were not directly transferable to the design of the new units due to 

differences in hydraulic characteristics as shown by model studies. Appropriate 

modifications were made (Swan, et al., 1990). Tests of full extended screens were also 

initiated at The Dalles and Little Goose Dams in 1993 (Gessel, et al., 1994). At McNary 

Dam extended length screens, either bar screens or submerged traveling screens have 

produced estimates of fish guidance efficiency of over 80 percent for yearling chinook 

(81 percent for the extended bar screen and 88 percent for the extended submerged 

traveling screen), Table 6 (McComas, et al., 1993). For sub yearling chinook, fish 

guidance efficiency of 67 percent was measured with the extended submerged traveling 

screen and 52 percent with the extended bar screen. 

At Little Goose Dam, tests of the full prototype in 1993 and 1994 brought fish 

guidance efficiencies of greater than 80 and 77 percent for yearling chinook, Table 6 

(Gessel, et al., 1994, 1995). For steelhead, fish guidance efficiency averaged 90 percent 

in the best configuration. No significant increases in descaling were observed for the 

extended screen at Little Goose Dam in comparisons with a standard submerged traveling 

screen (Gessel, et al., 1994, 1995). 

Recently, a question was raised as to whether these measurements of fish 

guidance efficiency for the extended screens may not be directly comparable to the 

measurements for the standard screens (personal communication with James Ceballos, 

NMFS/NOAA, Portland, Oregon). Because the measurements for the extended screens 

were made with the array of fyke nets in the bulkhead slot rather than in the gatewell slot 

upstream, it is thought that the estimates of fish guidance efficiency for the extended 

screens may be on the high side. This question is currently being evaluated. 

33 
Effectiveness of Fish Bypass Systems: Fish Guidance Efficiency, 

Mortality, Descaling, and Stress 

Introduction 

As noted previously, the primary criterion in evaluating the effectiveness of 

mechanical bypass systems is their fish guidance efficiency (FGE), i.e. the percentage of 

fish approaching the powerhouse that are diverted from the turbine intakes into the 

system. In the case of turbine intake screens, impingement and injury of diverted fish are 

problems that have had to be addressed by manipulations of screen openings, angle of deployment of the screen, velocity at the screen and other factors. 

Fish Guidance Efficiency (FGE) 

Estimates of fish guidance efficiency are variable from one test to another. 

Estimates differ with respect to the project, design and configuration of the apparatus, 

fish species, degree of smoltification, time of day (particularly day versus night), and 

progress of the season (Swan, et al. 1983; Swan, et al., 1985; Swan, et al., 1986; Swan, 

et al., 1987; Swan and Norman, 1987; Giorgi, et al., 1988; Hays and Truscott, 1986; 

Peven, 1995; Peven and Keesee, 1992). Information on fish guidance efficiency included 

in Table 6 must be interpreted in that context. Because fish guidance efficiency estimates 

have improved due to modifications of the screens, we have attempted to provide in 

Table 6 the most recent applicable estimates of fish guidance efficiency for a given 

project. Older information is provided in some cases for comparison. 

An example of the variability of fish guidance efficiency measurements was 

mentioned above, with respect to studies at Bonneville Dam, where installation of an 

approach channel for a new navigation lock brought about a reduction in fish guidance 

efficiency measured at the first powerhouse (Krcma, et al., 1984; Gessel, et al., 1991). 

Modifications to the screen and its deployment brought fish guidance efficiency up to 26 

to 44 percent for yearlings and 20 to 32 percent for subyearlings (Krcma, et al., 1984). 

At the second powerhouse, fish guidance efficiency was poor at the outset, less than 25 

percent for yearling and subyearling chinook (Gessel, et al., 1993). Modifications of the 

apparatus and extensions of the turbine intakes into the forebay brought improvements by 

1986 to around 60 percent for chinook yearlings, 55 percent for subyearlings, and 46 

percent for steelhead (Gessel, et al., 1991). Further tests were conducted each year 

through 1989. Best observed fish guidance efficiency was 78 percent for chinook 

yearlings and coho, 69 percent for steelhead, and 25 percent for subyearling chinook 

(Gessel, et al., 1991). On the basis of these studies, a new configuration was 

recommended for full installation across the second powerhouse. (Gessel, et al., 1993). 

In most cases, the fish guidance efficiency measured applies to a prototype tested 

at the project in a series of tests over one or more seasons. The estimates given in Table 

6 are projections for the particular project based on a series of samples. Ordinarily, the 

sample is taken from one of three intake slots at a sample turbine, where fish that are not 

34 
guided are captured for counting in fyke nets in the intake behind the screen. Guided fish 

rise in the gatewell where they are removed and counted. In many instances, the samples 

came from one slot where the adjacent slots were not equipped with screens. Studies at 

Wanapum Dam verified that although flow patterns were affected by screens in the 

adjacent slots, the resulting fish guidance efficiency measurements showed little or no 

effect (mid-Columbia Coordinating Committee, 1995). Since 1995, with the ESA listing 

of Snake River stocks, hydroacoustic methods have been employed for measurement of 

fish guidance efficiency at the Snake River and lower Columbia River dams, rather than 

fyke nets. 

In summary, estimated fish guidance efficiency in presently installed systems or 

prototype extended-length screens tested and scheduled for installation range from 26 

percent (Bonneville I) to 88 percent for yearling chinook, with most (6 of 11) in the range 

of 65 to 80 percent. For steelhead, fish guidance efficiency ranges from 76 to 93 percent, 

with most (6 of 8) above 80 percent. For the two studies that were able to include coho, 

fish guidance efficiency estimates were 93 and 98 percent. For sockeye fish guidance 

efficiency ranged from 14 to 73 percent in 6 studies, with only 1 estimate above 53 

percent.4

 Wells Dam in the mid-Columbia reach is the only project in the basin with a 

bypass system for juvenile salmon that can achieve the fish passage goals established by 

FERC, the NPPC and NMFS/NOAA. (Although the NMFS/NOAA goals do not apply in 

the mid-Columbia reach.) 

 

4

 These ranges include measurements for extended length screens which, as mentioned earlier in the text

have come under question. (James Ceballos, NMFS, Portland, Oregon, personal communication) 

35 
TABLE 6. FISH GUIDANCE EFFICIENCY MEASURED AT COLUMBIA BASIN PROJECTS. MOST 

Because over the years improvem

ents have been m

ade in configurations of screens at the projects, early measure

historic interest and do not apply to the existing bypass systems. Som

e historic information from Bonneville Dam 

example, showing improvem

ent in fish guidance efficiency as turbine intake extensions were provided and flows 

were modified in other ways. (Sources: Cited in the table. Data for W

anapum and Priest Rapids dams from pers

Stuart Ham

mond, Grant County Public Utility District No 2, Ephrata, W

ashington. Data for Rocky Reach and Ro

personal com

munication Charles Peven, Chelan County Public Utility District No. 1, W

enatchee, W

ashington) 

PROJECT FGE NOTES MID-COLUMBIA PROJECTS W

ells (Fully equipped) 89% Skalski, (1993). Spring and Sum

m

er. Surface attraction dev

Hydroacoustic estimate provides no species separation. 

Rocky Reach 30.8% Combined species. Highest achieved for yearling chinook 3

for subyearling chinook 21.9%; for steelhead 40.2%; and sockeye 24.1%. None of the prototype screens tested 1985-

 and 1994 

m

et criteria. 

Surface collector device being evaluated, 1995. 

Rock Island  Second Powerhouse n/a Prototype screens tested at powerhouse no.2 determined to b unfeasible.  First Powerhouse (1994) 85.7% Yearling chinook 

29.6% Subyearling chinook during the spring outmigration 63.7% Subyearling Chinook during the sum

m

er 

60.9% Steelhead 64.4% Sockeye 

W

anapum 75% Yearling chinook in 1992 

50% Subyearling chinook in 1992 26% Sockeye, Ham

mond (1991) 

36 
Table 6. (Continued). Fish Guidance Efficiency Measured at Columbia Basin Projects. Most recent data

Priest Rapids 84% Average for chinook yearlings 

52% Average for sockeye, 76-90% Range for steelhead, Ham

mond (1991). 

SNAKE RIVER PROJECTS Lower Granite 

(Standard STS) 57.3% Yearling chinook (Swan, et al. 1990) 

77.3% Steelhead (Swan, et al., 1990) 

(Extended Screen - Sim

ulated) 

66% Yearling chinook (Swan, et al., 1990) 82.4% Steelhead (Swan, et al., 1990) 

Little Goose 

(Standard STS) 73% Yearling chinook - with raised gate (Swan, et al., 1986) (Extended Screen) 77.3% Yearling chinook (Gessel, et al., 1995) 

89.6% Steelhead (Gessel, et al., 1995) 

Lower Monumental 69% Yearling chinook (Gessel, et al., 1993) 

85.3% Steelhead (Gessel, et al., 1993) 35.2% Subyearling chinook (Ledgerwood, et al., 1987) 

Ice Harbor 78% Yearling chinook (Brege, et al., 1988) 

92% Steelhead (Brege, et al., 1988) 

LOW

ER COLUMBIA RIVER PROJECTS 

McNary 

(Standard STS) 83% Yearling chinook (Krcm

a, et al., 1982) 

76% Steelhead (Krcm

a, et al., 1982) 

34-46% Sub yearling chinook (Swan, et al., 1984) 

37 
Table 6. (Continued). Fish Guidance Efficiency Measured at Columbia Basin Projects. Most recent data

McNary (continued) 

(Extended STS) 

88% Yearling chinook (McComas, et al., 1994) 67% Sub yearling chinook (McComas, et al., 1994) 93% Steelhead (McComas, et al., 1994) 73% Sockeye (McComas, et al., 1994) 98% Coho (McComas, et al., 1994) 

John Day 75% Yearling chinook (Swan, et al., 1982) [Tests of John Day  configuration conducted at McNary Dam]

79% Steelhead (Swan, et al., 1982. [Tests at McNary Dam]88% Yearling chinook (Krcm

a, et al., 1983). [Tests at McNary D

87% Steelhead (Krcm

a, et al., 1983) [Tests at McNary Dam]

72% Yearling chinook (Krcm

a, 1985; Brege, et al., 1992) [Test at 

 D

a

y

D

a

m]

20% Subyearling chinook (Krcm

a, 1985; Krcma, et al., 1986) [T

 John Day Dam]

35% Subyearling chinook (Brege, et al., 1987; Brege, et al. 198841% Sockeye (Krcm

a, et al., 1986; Brege, et al., 1992) 

86% Steelhead (Krcm

a, et al., 1986) 

The Dalles

Standard STS 44-56% Yearling chinook (Krcm

a, 1985) 

71-80% Steelhead (Krcm

a, 1985) 

40-60% Sockeye (Monk, et al., 1987) 

38 
Table 6. (Continued). Fish Guidance Efficiency Measured at Columbia Basin Projects. Most recent data

The Dalles (continued) 

(Extended-length screens) Scheduled for installation in 1998 

69% Yearling chinook (Absolon, et al., 1995) 54% Subyearling chinook (Absolon, et al., 1995) 83% Steelhead (Brege, et al., 1994) 53% Sockeye (Brege, et al., 1994) 93% Coho (Brege, et al., 1994) 

Bonneville 

Powerhouse number 1 

(1981) 76% Yearling chinook (Krcm

a, et al. 1982) 

72% Subyearling chinook (Krcm

a, et al., 1982 

(1983) Measurements following modification of navigation channel 

21% Yearling chinook (Krcm

a, et al., 1984) 

24% Subyearling chinook (Krcm

a, et al., 1984) 

14% Sockeye (Krcm

a, et al., 1984) 

34% Steelhead (Krcm

a, et al., 1984) 

(1984) 26-44% Yearling chinook (Krcm

a, et al., 1984B) 

20-32% Subyearling chinook (Krcm

a, et al., 1984B) 

Powerhouse number 2 

32-46% Yearling chinook (Monk, et al., 1992) 

 11% Subyearling chinook (Gessel, et al., 1989) 

 4% Subyearling chinook (Gessel, et al., 1990). 

Measurements following full installation of turbine intake extensions 

36-57 Yearling chinook (Monk, et al., 1995) 23-42 Subyearling chinook (Monk, et al., 1994) 

Bonneville Dam is below criteria. The NPPC calls for shutdown of second powerhouse and provision of spill du

39 
Conduit to the Tailrace 

As the tests of intake screens proceeded with promising results, appropriate 

means were sought for encouraging movement of the fish upward in the gatewells, 

removing the guided fish from the gatewells on a mass scale, and providing an exit to the 

tailrace below the dam (Mighetto and Ebel, 1995). At Bonneville Dam’s first 

powerhouse, orifices were cut from the gatewells to the ice and trash sluiceway to 

provide an exit for fish. A vertical barrier screen (VBS) was installed in the gatewell to 

create an upward flow that would encourage movement of the fish toward the orifices 

near the surface. A dewatering system was provided at the end of the sluiceway, where 

water was pumped back into the forebay in order to reduce the volume of water that 

entered a 20 inch conduit leading to the tailrace. At McNary Dam and other Corps 

projects, a separate bypass flume was constructed within the ice and trash sluiceway. 

Evaluations of effectiveness of the systems led to improvements in designs, (Krcma, et 

al., 1982; Krcma, et al., 1983; Krcma, et al., 1984; Krcma, et al., 1985; Krcma, et al., 

1986; Swan, et al., 1982; Swan, et al., 1983; Swan and Krcma, 1986). 

Once diverted into the gatewells, guided fish exit from there by way of orifices 

that lead into a conduit to the tailrace. Orifice passage efficiency (OPE) is a measure of 

the percentage of fish that leave the gatewell during a specified time period, normally 24 

hours. Orifice passage efficiency of 70 percent is considered satisfactory (NRC, 1995, p. 

191). Various opening sizes and locations have been investigated for their effects on 

orifice passage efficiency (Mighetto and Ebel, 1995; Liscom, 1971). At Wanapum Dam,

two baffle systems in the gatewell were tested for their effects on orifice passage 

efficiency. The best system produced an orifice passage efficiency of near 90 percent 

(mid-Columbia Coordinating Committee, 1993). 

 

Mortality and Descaling of Juvenile Salmon in Bypass Systems 

Mortality and Descaling at the Screen 

Another factor in evaluating the effectiveness of intake screens is mortality of fish 

caused by striking the screen or other objects in the bypass system. A percentage of the 

approaching fish may strike the screen in passing and lose some scales. Other fish, 

particularly small sub-yearling chinook, may become impinged on the screen. Impinged 

fish are observed when the screens are raised for inspection during prototype tests. The 

number of impinged and descaled fish are collected at the time of the tests and are useful 

in evaluating the performance of the prototypes. For our purposes, the pertinent numbers 

are the percentage of dead and descaled fish in the bypass system as a whole. This 

percentage reflects the effects of the screen after the final design is adopted. We did not 

attempt to provide a thorough review of available information on direct effects of the 

screens, because it is difficult to relate the results to the final design and installation. The 

direct effects would have been measured during prototype tests. However, we provide 

some examples in the following paragraphs. 

Impingement rates of yearling chinook are negligible in properly tuned systems, 

but impingement of subyearling chinook may be “high” in prototypes (e.g. Peven, 1993). 

40
At Lower Granite Dam, impingement that had ranged from 0.04 to 3 percent was reduced 

to less than 1 percent by design changes to the extended length screen that was tested in 

1990 (Wik and Barila, 1990). 

Descaling, caused by contact with the screen, may be observed with fish diverted 

into the gatewells during prototype tests. Descaling standards have been developed that 

set a threshold level of a percentage of missing scales (Koski, et al., 1986). Implications 

of descaling are not clear, because no direct relationship with survival has been 

established. As an example, descaling of guided fish at Lower Granite Dam during 

prototype testing was estimated to be 1.7 percent (Wik and Barila, 1990). No significant 

increase in descaling of guided fish at McNary Dam was observed with the extended 

screen (McComas, et al., 1993) compared to a standard submerged traveling screen that 

was used as a control. 

Mortality of Juvenile Salmon in the Bypass System as a Whole 

Performance of the bypass system as a whole (as far as the sampler) is monitored 

daily at those projects equipped with sampling systems in the bypasses. Dead fish are 

observed in the samples. These deaths may have occurred at any location within the 

bypass facility, from the screen to the sampler. At Little Goose Dam in the years from

1981 to 1993, average annual mortality of juvenile salmon observed in the facility ranged 

from 0.9 to 6.2 percent, for chinook, 0.1 to 0.8 percent for steelhead and 0.6 to 6.3 

percent for sockeye; and at Lower Granite Dam from 0.3 to 1.2 percent for chinook, and 

0.1 to 0.4 percent for steelhead (Koski, et al., 1989; FTOT, 1994). At Lower Granite 

Dam, studies of delayed mortality due to effects of passage through the entire bypass 

produced estimated losses of 7.6, 4.4 and 5.1 percent in 1984, 1985 and 1986 (Mathews, 

et al., 1987, as summarized by Chapman, et al., 1991). However, in the years 1989 to 

1993, total facility mortality at McNary Dam ranged from 0.4 to 1.9 percent for chinook 

yearlings, from 1.2 to 5.0 percent for chinook sub-yearlings, from 0.2 to 1.5 percent for 

steelhead, and from 0.5 to 4.1 percent for sockeye (FTOT, 1994). 

In addition to this monitoring of fish at the sampler, there have been estimates of 

mortality using marked fish. At McNary Dam in 1983, mortality of marked yearling 

chinook during passage from the gatewells to the bypass sampler ranged from 2 to 4 

percent, depending upon the location of the gatewell (Park, et al., 1984). 

Gilbreath, et al. (1992) state that in the first years of evaluation in the 1980s, the 

bypass facilities at both power houses at Bonneville Dam had a number of internal 

mechanical problems. The Corps subsequently corrected these problems. Thus, the 

present internal systems have a minimum impact on fish. For example, in 1983, 

excessive delay and exhaustion of fish was documented at the Bonneville second 

powerhouse bypass system (Krcma, et al., 1984). Now, juvenile mortality within the 

Bonneville Dam bypass system, as measured at the bypass sampler, generally ranges 

from less than 1 to 4 percent (Ceballos, et al., 1993). The Corps reports that survival rate 

in bypass systems is approximately 97 to 98 percent (Corps Salmon Passage Notes, 

1992). 

Descaling of Juvenile Salmon in the Bypass System as a Whole 

41
Descaling is monitored daily in the samplers located in the Corps bypass system

(e.g. Koski, et al., 1989). As observed at that point, descaling may have occurred at any 

point in the system from the screen downstream. The following are examples of numbers 

observed. As a result of improvements in the system and its operation, descaling rates at 

Lower Granite Dam declined in 1988 to 1.7 percent of the total sample. Of these, 2.4 

percent of the chinook were defined as descaled, and 1.4 percent of the steelhead. This 

was an improvement over 1987, when the total rate was 3.3 percent (Koski, et al., 1989). 

It was also an improvement over 1981 and 1982 descaling rates that had been recorded as 

15.5 percent for chinook and 16.8 percent for steelhead in 1981, and 8.8 and 10.1 percent 

in 1982 (Koski, et al., 1985). 

At Little Goose Dam the combined rate in 1988 was 3.4 percent. At McNary 

Dam the rate was 10.4 percent. Muir, et al. (1995A) estimated there was addition of 2.8 

percent to the rate of descaling of river-run steelhead as a result of passage through the 

bypass conduit at Lower Granite Dam. They thought that the 7 percent descaling rate of 

hatchery steelhead observed after the fish passed through the bypass was not excessive. 

Sampler to Outfall and Below 

An additional source of mortality to guided fish is the portion of the conduit 

leading from the dewatering screens at the sampler to the tailrace. Marked fish released 

out of the north shore outfall at McNary Dam were recovered at half the rate of other 

release groups. This finding suggested that predation in the vicinity of the outfall was 

responsible for added mortality (Sims and Johnson, 1977). 

Results of studies at Bonneville Dam were initially surprising. The results 

indicated that survival in the bypass system as a whole, from gatewells to a point 

downstream of the outfall, was no better than survival in passing through the turbines 

(Ferguson, 1993; Ledgerwood, et al., 1990; 1991; Dawley, et al., 1992; Gilbreath, et al., 

1993). During 1987 and 1988, the first two years of the study at Bonneville’s second 

powerhouse, Ledgerwood, et al. (1991) reported that rates of recovery in the estuary of 

marked subyearling chinook that had transited the bypass were significantly lower than 

fish that had passed through the turbines. This finding indicated higher mortality of 

juvenile salmon in the bypass than in the turbines. In the following two years there was 

no significant difference in recovery rates, suggesting that the bypass was not 

accomplishing any reduction in mortality compared to the turbines (Ferguson, 1993). 

However, it was then found that the conduit itself contributed only an estimated 3 percent 

mortality to juvenile salmon diverted by the intake screens (Dawley, et al., 1992). 

Therefore, Dawley, et al. (1992) and Gilbreath, et al. (1993) concluded that the primary 

source of mortality was outside of the bypass itself. The location of the outfall, in a place 

where predators could congregate, was identified as the most likely source of the high 

mortality measured by Ledgerwood, et al. (1991). 

Ledgerwood, et al. (1994) have begun a similar study of survival in the bypass 

and turbines at Bonneville’s Powerhouse I. First year study results indicated, as with the 

bypass at the second powerhouse, that survival of juvenile salmon was lower for 

juveniles that passed through the bypass than for juveniles that passed through the 

turbines. Again, predation at the outfall was thought to be the principal source of 

mortality. Tom Poe of the U.S. Fish and Wildlife Service (now U.S. Geological Survey) 

42
reported to Ledgerwood, et al. that a higher proportion of marked fish released into the 

bypass were consumed by northern squawfish in the tailrace than were other groups of 

fish released at the same time. 

Ferguson (1993) observed that bypass evaluations at other mainstem

hydroelectric projects have been limited to assessing survival at a collection point within 

the system, but not below the tailrace. Chapman, et al. (1991) recommended further 

research to evaluate mortality associated with bypass. 

Stress as it Affects Juvenile Salmon in Bypasses 

Concerns have been expressed about levels of stress induced on the juveniles as 

they encounter the screens and associated bypass systems (Congleton, et al., 1984; 

Schreck, et al., 1984). Bjornn (1992) found no difference in survival rates of marked 

chinook that were subjected to high stress prior to release as juveniles compared to those 

that were not stressed. 

Summary of Fish Guidance Efficiency, Mortality 

and Descaling in Bypass Systems 

Following studies by NMFS/NOAA and others, a set of criteria for successful 

bypass systems has been developed and approved by NMFS/NOAA, and fisheries 

agencies form Wahington, Oregon and Idaho. These criteria are available from NMFS 

Environmental and Technical Services Division in Portland, Oregon. They are 

reproduced as Appendix A in Neitzel, et al., 1997. These criteria establish maximum

velocities, advise avoidance of pressurization, set appropriate angles for curves and 

changes in elevation, set standards for dewatering and other factors in design (Rainey, 

1995; Bates, 1992; NMFS/NOAA, 1990). These criteria are being used in the design of 

bypass systems at Rocky Reach, Wanapum and Priest Rapids dams, and in the 

improvement of systems at Corps projects. In addition to providing criteria for 

performance of juvenile fish screens, NMFS has adopted a policy statement that provides 

for development and evaluation of new technology under controlled conditions (Office of 

Technology Assessment, 1995, recorded in their Appendix B.) 

Implementation of Findings on Turbine Intake Screens 

Success with tests of prototype screens has led either to their installation or to 

schedules for installation at most of the projects in the mid-Columbia, Snake and lower 

Columbia rivers. Details on FERC, NPPC, and NMFS/NOAA requirements and 

resulting installations are provided in Appendix A. The Corps has installed standard 

submerged traveling screens at all of their projects except The Dalles. Now, in response 

to NMFS/NOAA and NPPC requirements, installation of extended length screens was 

scheduled by the Corps for 1996 at Lower Granite, and Little Goose dams, for 1997 at 

McNary Dam, and for 1998 at John Day Dam (Corps, 1992; 1995). The bar screen 

design is being used in these installations, rather than the submerged traveling screen. 

Projects not yet equipped with turbine intake screens are The Dalles, Priest Rapids, 

Wanapum, Rock Island, and Rocky Reach dams (Corps, 1992; mid-Columbia 

43
Coordinating Committee Findings 1993). Wells Dam also is not equipped with turbine 

intake screens but has a different type of bypass, which is explained later in the report. 

Intake screen prototypes have been tested with success and schedules set for installation 

at The Dalles (1998), Priest Rapids and Wanapum dams. At Rocky Reach Dam,

prototype tests of intake screens annually from 1985 to 1994 did not produce satisfactory 

results (Peven, et al., 1996). At Rock Island Dam, the idea of screening powerhouse 

number 2 was abandoned, based on poor performance of prototypes tested, while at 

powerhouse number 1, tests have shown some promise and are continuing (Peven, 1995). 

 Although it is not associated with a dam, the hydroelectric facility at Hanford 

(Hanford Generating Plant) should be mentioned here. It has a cooling water intake with 

six bays, each equipped with a traveling screen designed to protect juvenile fish (Stone 

and Webster, 1987). Average survival of chinook yearlings encountering the screen was 

found to be 97.9 percent (Page, et al., 1975). 

Summary of Effectiveness of Bypass Systems 

In the final analysis, effectiveness of bypass systems must be evaluated in terms 

of their ability to achieve performance goals established by FERC, the NPPC and 

NMFS/NOAA. We provide a detailed evaluation in Appendix B, where we describe the 

goals, and the efforts to achieve them at each project, using the experience in 1995 as an 

example. In summary, the goals of NPPC and NMFS/NOAA are stated as 80 percent 

fish passage at each project. The NMFS/NOAA goals apply to the Snake River and 

lower Columbia River, while the NPPC goals apply to the basin as a whole and the FERC 

goals apply only to the Public Utility District projects in the mid-Columbia reach. The 

NPPC goals apply to time periods that are different from the NMFS/NOA time periods. 

FERC requirements for the mid-Columbia projects differ from project to project and do 

not correspond with the NPPC goals. None of the intake screens in place at the Snake 

River or lower Columbia River projects achieve fish guidance efficiency high enough to 

reach the 80 percent fish passage goal. Thus, it is necessary to add spill in sufficient 

quantities to make up the difference between a "standard" fish guidance efficiency and 

the fish passage goal. Spill amounts are therefore different from project to project 

because of differences in fish guidance efficiency, differences in spill effectiveness 

among projects, and changes in mixes of species between spring and summer. The result 

is a complex situation that we explain in detail in Appendix B. 

Analysis by the Fish Passage Center (1995) showed that the NMFS/NOAA or 

NPPC goals for 80 percent fish passage were not met at any of the Snake River or lower 

Columbia River projects in 1995, except at Ice Harbor Dam. At Ice Harbor Dam, 80 

percent fish passage occurred only because turbines were out of operation, which 

necessitated spill in amounts that led to production of gas saturation levels that went 

beyond permitted levels. At none of the other Snake River or lower Columbia river 

projects were the fish passage goals achieved, because spill amounts required to 

supplement the fish guidance efficiencies to reach the goals could not be provided. The 

spill amounts were reduced in practice because of limitations on gas saturation levels that 

were permitted. See Appendix B. The experience in 1995 is not unique. It represents a 

good example of a year with flows that are average or below. In years of high flow, 

44
hydraulic capacities of the projects will be exceeded, leading to spill in amounts that will 

lead to gas saturation levels above the permitted levels of 120 percent. 

Surface Collection Devices 

Ice and Trash Sluiceways 

Ice and trash sluiceways are in good position to attract fish approaching the 

powerhouse, because they are located at the surface directly above the turbine intakes and 

are included at the time of construction at some projects. Juvenile salmon were observed 

in the sluiceways at Bonneville (first powerhouse) and The Dalles dams. This 

observation led to initial testing of juvenile salmon passage through sluiceways 

(Michimoto and Korn, 1969). Efficiency of the sluiceways in diverting juvenile salmon 

from the turbine intakes generally ranged from 20 to 40 percent (Nichols, et al., 1978; 

Willis and Uremovich, 1982; and Willis, 1982, 1983). However, Giorgi and Stevenson 

(1995) point out that because major modifications were made to the bypass system at the 

Bonneville Dam Powerhouse I in the early 1980’s, it is doubtful that those estimates 

would apply under current conditions. In 1987, at the Bonneville Dam second 

powerhouse, the ice and trash sluiceway was shown to pass an estimated 81 percent of 

juvenile salmon passing the powerhouse in the daytime and 30 percent at night (Magne, 

1987). 

At The Dalles Dam, as previously discussed under the subject of spill 

effectiveness, the sluiceway passed an estimated 40 percent of the fish approaching the 

project when there was no spill (Willis, 1982). Confirming Willis’ results at The Dalles 

Dam, hydroacoustic studies showed fish were more concentrated in the volume of water 

entering the ice and trash sluiceway than in water entering the turbines (Nichols and 

Ransom, 1980; 1981; Steig and Johnson, 1986). At Ice Harbor Dam, the sluiceway was 

estimated to pass 48 percent of the migrants in the daytime in 4 percent of the water, and 

pass 21 percent of the migrants at night in 6 percent of the water (Ransom and Ouellette, 

1991) 

There is much current interest in surface collection devices, including ice and 

trash sluiceways for passing juvenile salmon. Investigations that are under way are 

described below. 

Wells Dam Hydrocombine 

The hydrocombine at Wells Dam is uniquely designed. Its spillway is located 

directly above the turbine intakes. This design provided a situation in which it was 

thought that juvenile salmonids that were observed to enter the turbines near the ceiling 

might be diverted into the spillbays above. 

Two-dimensional model studies were undertaken that were designed to determine 

the feasibility of altering the approach flow to direct the juvenile salmonids away from

the turbine intakes (under the leadership of Mike Erho and the late John Gregg; see 

Johnson, Sullivan and Erho, 1992; Sverdrup and Parcel Assoc. Inc., 1982; Johnson, 

Giorgi and Erho, 1997). The design included placement of solid covers on the turbine 

intake emergency gate slots, opening the flap gate in the top leaf of the spillway gate 

45
(surface spill), and installing solid baffles in front of the spillway to a point 30 to 40 feet 

below the surface, Figure 5. Testing of a prototype began in 1983 (Biosonics, 1983B). 

Alternative dimensions and configurations of openings in the intake baffles were tested in 

prototype in the next several years. These tests showed that a vertical slot configuration 

in the center baffle of three spillbay baffles was most effective at diverting fish (Sullivan 

and Johnson, 1986). The volume of water required for operation of the bypass varies 

somewhat depending on river flow and the powerhouse load. In 1995 it ranged between 

1.2 and 7.5 percent of the daily average river flow. 

One difficulty arising from the surface collection concept is that it requires a 

different method of evaluation than the method used to measure fish guidance efficiency 

with the turbine intake screens. With a surface collection device in prototype, 

investigators are faced with the practical problem of not being able to directly associate a 

fyke net catch in an intake with an assignable number of guided fish that may be drawn 

from a wide area across the powerhouse. The hydroacoustic method was used at Wells 

Dam in evaluating the performance of the surface collector. Currently, the hydroacoustic 

method is being employed in general for evaluation of intake screens. This is being done 

because of concerns about the impact of sampling with fyke nets where Snake River 

stocks are present. Also, it is questioned whether the presence of the fyke net array may 

itself affect measurement of fish guidance efficiency through influence on water 

movement (e.g. Thorne and Kuehl, 1989, 1990; Magne, et al., 1989; Stansell, et al., 1990; 

1991). A major disadvantage of the hydroacoustic method is that it is not possible to 

estimate fish guidance efficiency separately for each species of salmon, as it is with fyke 

nets. This is particularly important for fall chinook and sockeye, which have shown low 

fish guidance efficiencies, Table 6. 

At Wells Dam, initial evaluations were based on hydroacoustic counts in a set of 

spillbays and the associated turbine intakes directly below them. The final measurements 

of fish passage effectiveness were based on timed samples across the entire 

hydrocombine after the project was fully equipped with the bypass (Biosonics, 1983B; 

Kudera, et al., 1990; Skalski, 1993) 

46
Figure 5. Wells Dam hydrocombine, as a three dimensional schematic cross section. 

Direction of flow is from lower right hand corner of the diagram to upper left hand 

corner. The dark areas on the upstream face of the dam and sidewall are panels placed 

across the entrances to the spillbays. Note the vertical opening in the middle panel, 

labeled the C slot, which is not present in the A or B slots. Note also that the second B 

and C slots are shown with panels removed in order to provide a picture of their 

appearance without the panels. In the full installation, panels are present across the full 

face of the hydrocombine. (Source: Johnson, Giorgi and Erho, 1997) 

47
Implementation of Surface Collection at Wells Dam 

By 1987, a sufficient array of baffles was in place across the powerhouse at Wells 

Dam that it was operated as though it was complete. Spill beyond the amount necessary 

to operate the bypass has not been required for fish passage since then (Kudera and 

Sullivan, 1993). The system was fully installed in 1989. 

In January 1991, FERC approved a long-term settlement agreement that was 

developed by parties to the mid-Columbia agreement and applies to issues at Wells Dam. 

The agreement calls for operation of the juvenile fish bypass during the spring and 

summer outmigrations, at times to be determined by representatives of the parties to the 

mid-Columbia Proceeding. Among other things, the agreement called for a three-year 

study to measure the effectiveness of the bypass. It established a bypass criterion of at 

least 80 percent of the juvenile salmon for the spring period and at least 70 percent for 

the summer. From the resulting studies, the three year average bypass effectiveness 

during both the spring and summer outmigrations was estimated to be 89 percent 

(Skalski, 1993). It is currently the most effective bypass system in the basin, and the 

only one that can meet the standards for fish passage set by FERC, the NPPC, or 

NMFS/NOAA, without adding spill. (The NMFS/NOAA standard does not apply in the 

mid-Columbia because endangered Snake River chinook and sockeye are not found 

there.) 

Rocky Reach Dam 

The success at Wells Dam has stimulated studies of the possibility of applications 

elsewhere, as recommended by Bevan, et al. (1994). The technology used at Wells Dam

is not directly transferable to any other mainstem or Snake River project in the basin 

because Wells Dam is a hydrocombine. Unlike any of the other dams, the Wells Dam

spillway is located directly above the turbine intakes.5

 The failure of conventional intake 

screens that had been tested in prototype from 1985 to 1992 at Rocky Reach Dam was a 

factor in the decision to study a surface collection device, which was prepared for testing 

in 1995 (Peven, et al., 1995). 

It was estimated that in 1995 over 725,000 juvenile salmon and steelhead passed 

through the prototype device during the spring outmigration, April 26 to June 15 (Peven, 

et al., 1995). Development of the concept is proceeding (Peven, 1996). Surface 

collection is also being investigated for juvenile fish bypass at Rock Island Dam.

 

Wanapum Dam 

A parallel effort to develop a surface oriented juvenile bypass system began at 

Wanapum Dam in 1995 (Ransom, et al., 1995). The physical conditions at Wanapum

Dam are much different from conditions at either Rocky Reach or Wells dams. At 

Wanapum Dam, the spillway portion of the dam is downstream of the powerhouse, and 

 

5

 The Cowlitz Falls Project on the Cowlitz River is a hydrocombine design where the Wells concept is 

being tested (Solonsky, et al., 1995). 

48
the reservoir is much wider. Hydroacoustic evaluation brought estimates of fish passage 

efficiency in relation to unit 8 of 12.2 to 68.8 percent and averaged 35 percent for the 

spring migration season. Grant County Public Utility District plans to enlarge the 

prototype for testing in 1996. (Personal communication Stuart Hammond, Grant County 

Public Utility District) 

Ice Harbor and Other Corps of Engineers Projects 

Bevan, et al. (1994) and the NMFS/NOAA Proposed Recovery Plan refer to the 

success at Wells Dam and call upon the Corps to investigate potential applications at 

Corps projects. Accordingly, in 1995 the Corps conducted several studies of prototype 

surface collection configurations at Ice Harbor Dam. Three types of surface collectors 

were installed: vertical slots in front of two turbine intake slots (in conjunction with the 

ice and trash sluiceway), a sluiceway surface skimming gate, and stop logs that allowed 

surface spill at two spillbays (Swan, et al., 1995). The effectiveness was evaluated by 

radiotelemetry of juveniles and by hydroacoustics. The hydroacoustic study showed that 

the density of juvenile salmon was greatest in the sluiceway, although more total fish 

passed in spill because of the high volume of spill (Biosonics, 1995). Further tests are 

scheduled for 1996 at Lower Granite and The Dalles dams. 

CONCLUSIONS 

1. Juvenile salmon mortality in turbine passage is between 2.3 and 19 percent. 

Concern about this mortality has led to the development, construction and operation of 

bypass systems at all of the projects on the mainstem Columbia River and in the Snake 

River except The Dalles, Rocky Reach, Rock Island, Wanapum and Priest Rapids dams. 

The Dalles Dam has used the ice and trash sluiceway to pass at least 40 percent of the 

juvenile salmon approaching the dam.

2. Only turbine intake screens, surface collectors and spill have been found to be 

sufficiently successful in bypassing adequate percentages of juvenile salmon at the dams

to justify full installation. Many other approaches have been tried. 

3. Turbine intake screens have been the primary choice by the Corps at their 

projects. The Corps has a schedule for replacement of standard screens and installation 

of extended-length screens at all eight of their projects, including The Dalles. 

4. Whether it be through spill, intake screens or surface collection, the most 

successful bypass systems have taken advantage of a surface orientation of juvenile 

salmon as they move downstream. 

5. Effectiveness of turbine intake screens seems to have reached an upper limit 

that is less than the surface collector at Wells Dam, which passes 89 percent of the fish 

that approach the dam. Intake screens are unlikely to prove 100 percent effective in 

diverting juvenile salmon (Office of Technology Assessment, 1995, p.127). Although 

some measurements of effectiveness of extended screens showed values as high as 93 

percent for steelhead and coho, and 88 percent for chinook yearlings, none of the screens 

tested to date approach that value for subyearling chinook or sockeye, most of which are 

less than 50 percent, Table 6. 

49
6. Although extended length screens have demonstrated improvements over 

standard length screens, their fish guidance efficiency for subyearlings chinook are still 

below criteria set for fish passage by the NPPC and NMFS. The NPPC criterion is for 80 

percent fish passage at each Snake River project from April 15 to July 31, and at each 

Columbia River project from May 1 to August 31. The NMFS Snake River Salmon 

Recovery Plan criterion is for 80 percent fish passage at each Snake River project from

April 10 through June 20, and at each Columbia River project from April 20 through 

June 30. The inability to meet the criteria with extended length screens presents a 

particularly difficult problem in the Snake River, where subyearling chinook are listed as 

threatened or endangered, and in the lower Columbia River through which these fish 

must pass. 

7. Spill is effective as an interim measure, or a supplement to mechanical 

bypasses, that has been shown to offer high survival of fish up to the point where 

supersaturation of atmospheric gas becomes a problem. 

8. Fish guidance efficiency of turbine intake screens varies widely from project 

to project because of many factors, particularly the species of fish. Spill effectiveness 

also varies, particularly among projects and has not been measured at many Corps 

projects. Thus, the determination of spill levels, that are set each year to attain the NPPC 

or NMFS/NOAA passage goals, is complex and requires assumptions that go 

considerably beyond available information. 

9. Because of limits on gas saturation and the high levels of gas produced by the 

spill amounts required to supplement fish guidance by intake bypass screens, the NPPC 

and NMFS goals of 80 percent fish passage cannot be achieved at any project except 

Wells Dam. Measures are needed to reduce gas saturation levels when spill is to be used 

as a bypass measure to achieve the 80 percent fish passage goals. Further studies in the 

open river are needed in order to establish the appropriate upper limit for gas saturation 

that can be tolerated by salmon in the natural situation.

10. The most effective spill is surface spill. Spill spread over 24 hours a day was 

more than twice as effective per unit volume of water used than night-time spill for 12 

hours at Priest Rapids Dam. 

11. Effectiveness of spill differs among the projects. More information is needed 

at most of the Corps projects. In addition, effectiveness of surface spill needs to be 

defined at each project, along with determination of the effects of spilling for different 

time intervals, such as spilling for 24 hours per day versus 12 hours. 

12. The NPPC criterion of 98 percent smolt survival within bypass and collection 

systems from the screen to the end of the outfall that is specified in the 1994 Fish and 

Wildlife Program appears to be attainable. However, losses due to predation at the 

outfalls and in the tailraces can be substantial in some situations. 

13. Surface collectors are the most promising devices for attaining the fish 

passage goals established by the Council in the fish and wildlife program or 

NMFS/NOAA in the Snake River Salmon Recovery Plan. 

14. Current developments are shifting toward provision of surface spill and 

surface collection, as opposed to turbine intake screens for bypass of juvenile salmon. 

The attractiveness of surface spill and surface collection over standard spill comes from

the possibility of passing a high percentage of the juveniles of all species and sizes in a 

small volume of water by taking advantage of the natural behavior of the fish. 

50
15. Modification of ice and trash sluiceways offers a potentially effective means 

of providing a surface exit for juvenile salmon. 

51
APPENDICES 

INTRODUCTION 

The Appendices draw upon the review of studies contained in the text. In the 

interest of continuity and brevity, we have omitted citations to sources here wherever 

statements are supported in the text. They may be found under the appropriate headings 

there. Appendix A lists the specific requirements by the Federal Energy Regulatory 

Commission (FERC), the Northwest Power Planning Council (NPPC), and the National 

Marine Fisheries Service (NMFS/NOAA) for installation and operation of bypass 

facilities at each project. It also lists the bypass systems that are in place or scheduled for 

installation at each of the 13 projects on the mainstem Columbia and Snake rivers. 

Appendix B is in two parts. Part 1 describes the fish passage goals of FERC, the NPPC 

and NMFS/NOAA. Part 2 evaluates the effectiveness of the bypass systems in achieving 

the goals in 1995 as an example. The NPPC and NMFS/NOAA specify a goal for fish 

passage efficiency (FPE), which is the percentage of fish approaching a project that is 

diverted away from the turbine intakes either through a bypass system or spill. The 

bypass system at Wells Dam is the only one that can achieve the fish passage efficiency 

goals without the addition of spill. Fish passage efficiency at the other projects depends 

upon the sum of the fish guidance efficiency (FGE) of the bypass system and the 

effectiveness of spill in passing fish. Requirements for spill by the NPPC and 

NMFS/NOAA are discussed in Appendix B because they have to be considered in the 

context of the fish passage goals and the effectiveness of the bypass systems that are in 

place. 

APPENDIX A: REQUIREMENTS BY FERC, THE NPPC AND NMFS/NOAA 

FOR INSTALLATION OF MECHANICAL BYPASS SYSTEMS 

FERC and NPPC Requirements in mid-Columbia 

Background 

 

The FERC regulates the operations of the five non-federal dams in the midColumbia Reach. The FERC has established requirements for operation of these projects 

to provide for increased survival of migrating juvenile salmon in the spring and summer. 

Because only Wells Dam has a bypass facility in place, spill is required at the other 

projects as an interim measure for passage of juvenile salmonids. FERC requirements, 

applying to the public utility district projects in the mid-Columbia have, as a rule, been 

repeated by the NPPC as requirements in the Council's fish and wildlife programs. In the 

mid-Columbia Settlement Agreement of 1979 and subsequent stipulations, the parties to 

the mid-Columbia FERC proceeding agreed to work together to improve production of 

salmonids. Methods agreed upon included provision of spill, investigation of diversion 

of smolts from intakes, and collection and transportation of smolts (Offer of Settlement. 

52
Public Utility District Number 2 of Grant County, Washington. 10 FERC ¶ 61,257 

(1980) Adopted by FERC March 23, 1980). 

FERC Requirements for Juvenile Fish Passage including Spill 

Wells Dam 

 

Surface Collector. The settlement agreement for Wells Dam, adopted by FERC, 

set a fish passage goal for the bypass of 80 percent for spring migrants and 70 percent for 

the summer. As described in the body of the text, there is a bypass system in place, a 

surface collector that achieves 89 percent fish passage efficiency in both spring and 

summer. It is operated during spring and summer at times that are agreed upon by the 

Wells Project Coordinating Committee. The committee consists of parties to the midColumbia Proceeding, which includes representatives of Douglas County Public Utility 

District, the fishery agencies, and tribes. 

Spill. No spill is required for fish passage at Wells Dam because the bypass 

system has higher fish passage efficiency than the 80 percent in spring and 70 percent in 

summer required by FERC. 

Rocky Reach Dam 

 

 Intake Screens. As agreed in the mid-Columbia Settlement Agreement, prototype 

submerged traveling screens of various configurations were tested from 1985 to 1988 

(Peven and Keesee, 1992). Bar screens of various configurations were then tested from

1989 to 1992. None performed satisfactorily. Highest measured fish guidance efficiency 

for chinook yearlings was about 50 percent. It was concluded that it would not be 

possible to meet criteria with intake screens at that project (Peven and Keesee, 1992). 

The project has a peculiar configuration. A powerhouse is nearly parallel to the river 

flow and a cul-de-sac is between the powerhouse and the right bank. This configuration 

led to development of unusual flow patterns that affect fish behavior. The unusual 

configuration and flow pattern are thought to be factors in the inability to apply the 

screen technology to this project. 

Surface Collector. In 1995, testing began of a surface collection device. The 

prototype being tested shows promise. Further tests of a modified device were scheduled 

for 1996 and 1997. 

Spill. (FERC). In a stipulation with FERC for 1994 and 1995, spill levels at 

Rocky Reach Dam were specified as 15 percent for 30 days during the spring 

outmigration. An option was included to increase the number of days by up to 6 

additional days if necessary to encompass 90 percent of the Okanogan River sockeye 

outmigration. Levels were specified as 10 percent for 34 days between June 15 and 

August 15. 

Spill. (NPPC). The 1987 Fish and Wildlife Program called for 20 percent spill at 

each of the mid-Columbia public utility district projects. However, the 1994 Fish and 

Wildlife Program merely calls upon the parties to the mid-Columbia Proceeding to 

annually develop plans for spill at Rocky Reach and Rock Island dams. 

53
Rock Island Dam 

 

Intake Screens. Rock Island Dam was removed from the mid-Columbia 

proceeding in 1984 when issues with respect to the need for intake screens were 

undergoing hearing with the FERC. A long-term settlement agreement was reached in 

1987 and adopted by FERC. The agreement included a provision for evaluation of 

prototype intake screens at both powerhouses. Following tests of prototypes, Chelan 

County Public Utility District concluded that installation at the second powerhouse was 

not feasible due to the limited space available in front of the horizontally oriented bulb 

turbines. Tests at the first powerhouse have shown some promise, with fish guidance 

efficiency measured in the range of 70 to 75 percent for chinook yearlings, about 60

percent for chinook subyearlings, and 45 to 55 percent for sockeye in 1994 (Peven, 

1994). 

Surface Collector. Chelan Public Utility District is investigating the feasibility of

using a surface collection device at Rock Island Dam that might serve both powerhouses. 

Spill. The settlement agreement allowed for substitution of spill valued at 

$1 million (in 1986 dollars) if no screens are installed at the second powerhouse, at the 

option of the parties to the proceeding. As of 1996, this option has not been invoked. On 

issues relating to Rock Island Dam, the Long-term Settlement Agreement of 1987 did not 

include provision for interim spill. A clause in the agreement did provide for substitution 

of spill for bypass development. However, in 1985 FERC ordered spill as an interim

measure at a level of 10 percent spill of the volume of water passing through the second 

powerhouse and 50 percent of the volume that would have gone through the first 

powerhouse in the absence of spill. 

Wanapum and Priest Rapids Dams 

 

Intake Screens. The FERC agreement of 1979 called for tests of intake screens at 

Wanapum and Priest Rapids dams. Based on the success of the fixed bar screen design 

demonstrated by the earlier NMFS/NOAA tests, the Grant County Public Utility District 

used the fixed bar design with other desirable features for prototype tests at Priest Rapids 

Dam. Prototypes were tested at Priest Rapids Dam from 1986 to1988. The tests 

produced fish guidance efficiencies satisfactory to representatives of the mid-Columbia 

Coordinating Committee. 

The intake geometry at Wanapum Dam is similar to Priest Rapids Dam, such that 

the screen configuration tested at Wanapum Dam was also similar. Attainment of fish 

guidance efficiency near 75 percent for yearling chinook during the spring and 50 percent

for sub-yearlings during the summer led to design and testing of an orifice passage 

system beginning in 1993. 

In 1992, Grant County Public Utility District proposed to install a full bypass and 

collection system at Wanapum Dam and to provide transportation of the collected fish for 

release below Priest Rapids Dam. This would have avoided the need for intake screens 

and an associated bypass system at Priest Rapids Dam. The parties to the mid-Columbia 

proceeding were unable to agree on this proposal. Grant County Public Utility District 

requested a hearing before a FERC administrative law judge, who ruled against the Grant 

County Public Utility District proposal and ordered installation of turbine intake screens 

54
[State of Washington Department of Fisheries v Public Utility District No. 2 of Grant 

County. FERC Proceeding. Docket No. E-9569-003 (Grant County Phase), re Project 

No. 2134-024. Ruling of March 23, 1992, Hon. Stephen L. Grossman presiding.] This 

ruling does not become final until it is formally adopted by FERC. 

Grant County Public Utility District is proceeding with design and installation of 

a full bypass system with completion scheduled for 1999 at Wanapum Dam and 2000 at 

Priest Rapids Dam. 

Surface Collector. Grant County Public Utility District is evaluating surface 

collection as an alternative to intake screens at Wanapum Dam. 

Spill. (FERC). In 1994, in response to a petition from the fishery parties, FERC 

required Grant County Public Utility District to provide spill for juvenile salmonids at 

Wanapum and Priest Rapids dams. The spill requirement was an interim fish protection 

measure. The spill amount was to be sufficient to ensure passage of 70 percent of the 

juvenile salmonids during 80 percent of the spring outmigration and 50 percent passage 

during 80 percent of the summer outmigration. (FERC Docket No. E-9569-003, Grant 

County Phase. Order of May 24, 1994). The effectiveness of these measures is reviewed 

in Appendix B. 

Spill. (NMFS/NOAA). The NMFS/NOAA Proposed Recovery Plan calls upon 

Grant County Public Utility District to install flip-lip spillways and/or a stilling basin at 

Wanapum Dam. Grant County Public Utility District planned to begin design for 

installation of flip-lips in the spillway at Wanapum Dam in 1996. 

NPPC Requirements in the Fish and Wildlife Program and 

NMFS/NOAA Requirements in the Proposed Recovery Plan 

NPPC Requirements for Mechanical Spill 

Requirements of the NPPC and NMFS/NOAA with respect to installation and 

improvement of bypass devices are somewhat similar. However, most of the Corps 

projects were equipped with intake screens either before the NPPC was formed or during 

the time when the NPPC's authority over this subject was not shared with NMFS/NOAA. 

Although the experiments with the bar screen showed promising results, there 

were difficulties with debris and the Corps elected initially to proceed with installation of 

submerged traveling screens (STS) at all eight of its projects on the Snake River and 

lower Columbia (Corps Salmon Passage Notes 1992). In the 1991 Amendments to the 

Fish and Wildlife Program and the 1994 Fish and Wildlife Program, the Council called 

for completion by 1998 of turbine intake screens and juvenile fish bypass systems at all 

of the Corps dams on the lower Columbia River and Snake River. All but The Dalles 

Dam are now fully equipped with intake screens. 

In addition, the 1994 Fish and Wildlife Program called for installation of extended 

length screens at McNary (1995), Lower Granite (1996), Little Goose (1996), John Day 

(1998), and The Dalles (1998), if they prove to be effective. 

Based on the studies that demonstrated improved fish guidance efficiency with 

extended-length screens, the Corps is proceeding with testing and installation of 

extended-length screens at the eight projects to replace the standard screens (U.S. Army

Corps of Engineers, 1996). Four of the projects, Lower Granite, Little Goose, Lower 

55
Monumental, and McNary dams were expected to be equipped in time for the 1996 

outmigration (Filardo, January 18, 1996 Memorandum to FPAC). As mentioned in the 

text, the extended length screens that are being installed are bar screens rather than 

traveling screens. 

NMFS/NOAA Requirements for Mechanical Bypass Systems 

The NMFS/NOAA Proposed Recovery Plan specifies a general strategy whose 

first two measures focus on: 1) improvements in downstream survival through increased 

flows and controlled spill in the Columbia and Snake Rivers; and 2) modifications to 

dams and their operations to bring about improvements in juvenile downstream passage 

survival and upstream adult survival (NMFS/NOAA, 1995, p. 1-8). 

To improve survival of juvenile salmonids in passage through turbines, the plan 

calls for operating turbines at the eight federal projects within 1 percent of peak 

efficiency during March 15 through October 31 in the Columbia River and March 15 

through November 30 in the Snake River. 

The plan provides strategies for installation, improvement, or testing of bypass 

facilities at each of the eight Corps projects. The plan also calls for installation of flip-lip 

spillways or a stilling basin at the base of the spillway at Wanapum Dam, as previously 

discussed. 

The plan calls for studies to improve efficiency in the bypass systems at Columbia 

Basin hydroelectric projects. It lists five kinds of studies, including studies that reevaluate the existing bypass systems, evaluate all new systems, develop new means of 

collection and bypass, develop better methods for counting fish that are bypassed and 

held, and assess the impacts of supersaturated gas on juvenile and adult salmonids. In 

addition, specific measures are called for at certain projects, as described below.

 Intake Screens. The Proposed Recovery Plan calls upon the Corps to reduce loss 

of juvenile fish through structural and operational improvements of bypass facilities. See 

the note above under NPPC, regarding the Corps schedule for installation of extended 

length intake screens at the eight Corps projects. 

Surface Collector. The Proposed Recovery Plan produced by the Snake River 

Salmon Recovery Team, referred to the success at Wells Dam and called for 

investigation of the application of surface collection technology at the Snake River and 

Columbia River projects, (Bevan, et al., 1994; NMFS/NOAA, 1995). Surface collector 

studies are proposed for 1996 in the Portland District of the Corps to cover: (a) hydroacoustic evaluations of fish passage, (b) fish condition studies, and (c) radio telemetry for 

fine scale behavior information of juvenile salmonids in the forebay, through surface 

passage routes, and through the tailrace at Lower Granite, The Dalles, and Bonneville 

dams, and for 1997 at Ice Harbor Dam (Draft Corps Mitigation Project 11/2/95). Criteria 

are to be developed to design, model and evaluate surface bypass devices. (Corps 

Workshop, 1995) 

 Flip-Lip Spillways. Five of the eight Corps projects were equipped with flip-lip 

spillways in 1995, Table A.1 (Detailed Fishery Operating Plan, (DFOP) 1993, and 

personal communication Larry Basham, Fish Passage Center). John Day, Ice Harbor and 

The Dalles dams were not equipped. At The Dalles Dam, the shallow spill basin is not 

believed to cause high gas saturation (personal communication, Larry Basham, Fish 

56
Passage Center, 1996). However, of the equipped dams, only Lower Granite Dam is 

fully equipped across the spillway. Equipped spill bays are used as the first alternative 

for spill. When spill exceeds the capacity of equipped bays the remaining spill bays are 

employed. 

________________________________________________________________________ 

Table A.1. Installation date and numbers of “flip-lip” spill bays at Corps projects. 

(From Detailed Fishery Operating Plan, 1993) 

Project Date Number of Flip-lips 

Lower Granite 2/75 8 of 8 bays 

Little Goose 2/76 6 of 8 bays 

Lower Monumental 

 

8/74 6 of 8 bays 

Ice Harbor Recommended by NMFS/NOAA Proposed 

Recovery Plan 

McNary 1/76 18 of 22 bays (2 outer bays on each end not 

equipped) 

John Day none 

The Dalles none (Spill through the shallow basin is thought not 

to cause high gas saturation) 

Bonneville 3/75 13 of 18 bays (3 outer bays on north shore and 2 

outer bays on south shore) 

 

NPPC AND NMFS/NOAA Requirements for Mechanical Bypass at 

Snake River Projects 

(Spill Requirements are complex and will be discussed in Appendix B.) 

Lower Granite Dam 

 

Intake Screens (NPPC). The 1987 Fish and Wildlife Program called upon the 

Corps to continue to evaluate and improve the effectiveness of the juvenile bypass 

system, to improve fish guidance efficiency, and continue studies to determine whether it 

was necessary to modify the existing juvenile fish bypass system to reduce mortalities 

and injuries. The 1991 Amendments to the Fish and Wildlife Program called for 

improvement of the existing fish collection and bypass system at Lower Granite Dam by 

March, 1996. Accordingly, the Corps modified gates in the bypass system in 1992. 

Intake Screens. (NMFS/NOAA). The Proposed Recovery Plan specifies that by 

1997, or as soon as possible, the Corps should develop a plan and proceed with 

improvement of the juvenile passage facility at lower Granite Dam. Some specific 

requirements for improvement are listed in the Plan 

Extended Length Screens (NPPC). The 1994 Fish and Wildlife Program showed 

a schedule for installation of extended length screens at Lower Granite Dam by March, 

1996. 

Extended Length Screens (NMFS/NOAA). The Proposed Recovery Plan calls 

upon the Corps to continue its planned installation of extended length screens in time for 

57
the1996 smolt migration season. The Corps indicates they will be ready in March 1996 

(Corps Salmon Passage Notes 1992). 

Surface Collector. (NMFS/NOAA). The Proposed Recovery Plan calls upon the 

Corps to investigate the application of surface collection technology by June 1996. The 

Walla Walla District proposed a test of a prototype surface bypass and collection device 

at Lower Granite Dam in 1996, with full installation to follow in 1997 and 1998, 

depending on the results of tests. The prototype to be tested in 1996 will include configurations similar 

to those found to be the most successful at Ice Harbor Dam in 1995 (Corps Workshop, 

1995) 

Little Goose Dam 

Intake Screens. (NPPC). Little Goose Dam was equipped with turbine intake 

screens when it began operation in 1970. However, after1979 to 1980 when the conduit 

was reconstructed to enlarge the system, juvenile mortality had increased. The 1987 Fish 

and Wildlife Program called upon the Corps to study whether it was necessary to modify 

the bypass system to reduce mortalities to juvenile fish. The fish and wildlife program

called for installation of improvements by April 1989. The Corps modified gates in the 

bypass in 1991. 

 Extended Screens (NPPC). The 1994 Fish and Wildlife Program showed a 

schedule for installation at Little Goose Dam by March 1996. Accordingly, the Corps 

has scheduled installation of extended screens at Little Goose by March 1996 (Corps 

Salmon Passage Notes 1992). 

Extended Screens (NMFS/NOAA). Extended Screens. The Proposed Recovery 

Plan called for the Corps to install extended length screens at Little Goose in time for the 

1996 smolt migration season. 

Lower Monumental Dam 

 

Intake Screens (NPPC). The Fish and Wildlife Program of 1987 called upon the 

Corps to develop a plan for installation of a juvenile fish bypass system and install a 

screening and bypass system at Lower Monumental Dam by April 1990. 

There is no sluiceway at Lower Monumental Dam, which greatly complicated the 

provision of a conduit for juveniles to the tailrace. The Corps therefore developed an 

alternate plan to use Lower Monumental as a collection facility for transportation. 

However, the Council felt the results were uncertain, and called for prototype testing of 

turbine intake screens there. The 1991 Amendments to the Fish and Wildlife Program

called for Lower Monumental Dam to be equipped with screens and a bypass system by 

1992. The Corps complied with installation. 

Extended Screens. (NPPC). The 1994 Fish and Wildlife Program calls upon the 

Corps to plan for installation of extended length screens and structural modifications to 

improve gatewell hydraulics, contingent upon the results of prototype testing at Little 

Goose and Lower Granite dams. 

Ice Harbor Dam 

 

 Intake Screens. (NPPC). The 1994 Fish and Wildlife Program called upon the 

Corps to provide a completed and operational screening and low-velocity flume bypass 

system by March 1996. The 1987 Fish and Wildlife Program had called for testing of 

58
screens in prototype and installation by April 1990. The 1991 Amendments to the Fish 

and Wildlife Program called for installation of screens and a bypass system at Ice Harbor 

by 1994. The Corps complied by 1994. Screens were in place in 1993 and the full 

bypass by 1994. 

Extended Screens. (NMFS/NOAA). The Proposed Recovery Plan calls for 

planning for extended length screens and structural improvements to improve gatewell 

hydraulics at Ice Harbor Dam, contingent upon the results of prototype screen testing at 

Little Goose and Lower Granite dams. 

Surface Collector. (NMFS/NOAA). The Proposed Recovery Plan adopted by 

NMFS/NOAA in 1995 states that testing of the surface collector concept will begin in 

1995 at Ice Harbor and The Dalles dams. Tests were to be implemented at Lower 

Granite Dam in 1996. The plan states that if successful, they should be installed in 1996 

at the projects where they have been tested. In 1995, the Corps conducted several studies 

of prototype surface attraction configurations at Ice Harbor Dam. 

Surface Spill. (No requirement). The Corps is investigating the possibility of

employing surface spill at Ice Harbor Dam, (Biosonics, 1995 Abstract presented at Corps 

Workshop, September 1995). 

Flip-lip Spillway. (NMFS/NOAA). The Plan calls for the Corps to install stilling 

basins and spillway modifications (such as a flip-lip) to reduce dissolved gas levels at Ice 

Harbor Dam as soon as possible. The Corps plans to design a flip-lip spillway for Ice 

Harbor Dam in 1996 and construct it in 1997. (Corps Columbia River Fish Mitigation 

Project Draft Plan, November 2, 1995.) 

NPPC AND NMFS/NOAA Requirements for Mechanical Bypass at 

Lower River Projects 

 

McNary Dam 

 

 Intake Screens. (NPPC). The Council’s Fish and Wildlife Program of 1987 called 

for the Corps to continue to evaluate and improve the effectiveness of the juvenile fish 

bypass system at McNary Dam, because of changes that had been made since 1968 when 

installation of the system was begun. 

Extended Screens. (NPPC). The 1994 Fish and Wildlife Program calls for 

extended length screens to be installed by March 1995. The Corps scheduled prototype 

tests for 1995, (Corps, 1992). 

Extended Screens. (NMFS/NOAA). The Proposed Recovery Plan calls upon the 

Corps to continue the scheduled installation of extended-length screens in 1997. The 

Corps completed installation in time for the 1996 outmigration. (Filardo memo, January 

18, 1996) 

Operate Bypass. (NMFS/NOAA). The Proposed Recovery Plan states that the 

bypass system should be operated according to criteria that will mitigate adverse warm

water conditions in the summer. It calls for shading over the raceways by the end of 

1995. 

 

John Day Dam 

59
Intake Screens. (NPPC). The 1987 Fish and Wildlife Program called upon the 

Corps to proceed with its plan to install a complete bypass system with turbine intake 

screens at John Day Dam. Screens and the bypass system were in place by 1993 (Corps 

Salmon Passage Notes, 1992). The 1994 Fish and Wildlife Program called upon the 

Corps to install extended length screens by March 1998. 

Extended Length Screens. (NMFS/NOAA). The Proposed Recovery Plan says 

that extended length screens should be installed at John Day Dam by spring, 1998. 

Surface Collector. (NMFS/NOAA). The Proposed Recovery Plan states that if 

testing of surface collection is successful at Ice Harbor and The Dalles, the Corps should 

proceed with testing at John Day Dam in 1997. The Corps has scheduled studies of 

surface collection at John Day Dam in 1997 and 1998. 

Flip-lip Spillway. (NMFS/NOAA). The Proposed Recovery Plan calls for the 

Corps to install stilling basins and spillway modifications (such as a flip-lip) as soon as 

possible at John Day Dam to reduce dissolved gas levels. The Corps intends to design a 

flip-lip spillway in 1996 and begin construction in 1997 for completion in 1998. (Corps 

Columbia River Fish Mitigation Project Draft Plan, November 2, 1995). 

 

The Dalles Dam 

 

Intake Screens. (NPPC). The 1987 Fish and Wildlife Program states that the 

Corps should proceed with installation of turbine intake screens at the Dalles Dam, where 

the Corps had depended upon an ice and trash sluiceway for juvenile fish bypass. 

Intake Screens. (NMFS/NOAA). The Proposed Recovery Plan says the Corps 

should continue designing a conventional intake screen system for installation at The 

Dalles. Following prototype testing, a decision should be made whether to continue 

developing a surface collection system or to proceed with installation of the screens by 

1999. 

Extended Screens. (NPPC). In the 1987 Fish and Wildlife Program, the Corps 

was called upon to complete prototype testing of extended screens by April, 1991, and to 

complete design and installation of a juvenile fish screen and bypass system by April, 

1993. The 1991 Amendments to the Fish and Wildlife Program called for the installation 

of screens and a bypass system at The Dalles by 1998. In 1992, the Corps scheduled 

installation of extended length screens by March 1998 (Salmon Passage Notes. Special 

Edition, 1992) 

Surface Collector. (NMFS/NOAA). The Proposed Recovery Plan notes that the 

Corps plans to test a surface collector at The Dalles Dam in 1995. The Corps will test the 

surface collector in 1996. 

Bonneville Dam 

 

Intake Screens. (NPPC). The 1987 Fish and Wildlife Program called upon the 

Corps to continue feasibility studies of means to improve juvenile fish guidance at the 

second powerhouse. Because of low fish guidance efficiency measured for the screens at 

the second powerhouse, the second powerhouse was to be closed when necessary to 

achieve an 85 percent juvenile fish passage through combinations of spill and bypass 

operation at Bonneville Dam. The Corps was called upon to provide annual progress 

reports until an 85 percent juvenile fish passage is achieved. 

60
As of 1995, this goal had not been attained. The 1991 Amendments to the Fish 

and Wildlife Program called for installation of improved screens and bypass at 

Bonneville Dam’s second powerhouse by March 1993, and evaluation of fish guidance 

efficiency at the first powerhouse. 

 Intake Screens. (NMFS/NOAA). The Proposed Recovery Plan calls for improved 

fish guidance efficiency at the Bonneville first powerhouse, with no date specified. 

Improve Bypass. (NMFS/NOAA). The Proposed Recovery Plan calls upon the 

Corps to relocate the downstream migrant outfalls at Bonneville Dam by spring 1999. 

Bypass survival tests at Bonneville Dam suggest that predation in the tailrace may be 

substantial (Ledgerwood, et al., 1990. See text.). The Corps should improve hydraulic 

conditions at the dewatering systems in both bypass systems at Bonneville Dam by the 

year 2000. 

61
APPENDIX B: IN TWO PARTS 

PART 1. GOALS FOR JUVENILE FISH PASSAGE BY FERC, NPPC 

 AND NMFS/NOAA 

PART 2. EVALUATION OF FISH PASSAGE ACHIEVED IN 1995 

Part 1. Goals for Juvenile Fish Passage 

by FERC, NPPC, and NMFS/NOAA 

FERC Requirements for Bypass and Spill 

There is a mix of requirements by FERC for provision of bypass of juvenile 

salmonids at the mid-Columbia projects. At Wells Dam, the requirement is for bypass of 

a specified percentage of the juvenile migrants, 80 percent during spring and 70 percent

during summer. At Wanapum and Priest Rapids Dams, the requirement is for bypass of 

70 percent during spring and 50 percent during summer. At Rocky Reach and Rock 

Island dams, the requirement is for a specified amount of spill during spring and summer. 

NPPC Requirements for Mechanical Bypass Systems and Spill 

In contrast to the mixed FERC requirements, both the NPPC and NMFS/NOAA 

have established fish passage goals that apply to all projects under their jurisdiction. 

Those goals are to be achieved using bypass facilities that are present along with spill as 

needed to achieve the fish passage goals. The NPPC in its fish and wildlife program has 

established goals for passage which apply to each of the projects in the Snake River and 

mainstem Columbia River, as well as the FERC projects in the mid-Columbia Reach. 

The 1994 Fish and Wildlife Program requires 80 percent fish passage efficiency 

(FPE) over specified spring and summer periods that are intended to encompass juvenile 

migrations in the mainstem Columbia and Snake rivers (NPPC 1994). Note the 

distinction between fish guidance efficiency (FGE) and fish passage efficiency (FPE). 

As previously explained, fish guidance efficiency is a measure of the percentage of fish 

diverted by screens in turbine intakes. Fish passage efficiency is a measure of the 

percentage of total fish passing a project through routes other than the turbines. These 

other routes include the intake bypass systems, spill, or the ice and trash sluiceways. The 

NMFS/NOAA goal is for 80 percent fish passage efficiency, but over different time 

periods than the NPPC. The NPPC schedule is from April 15 to July 31 at the Snake 

River projects and May 1 to August 31 at the lower Columbia River projects. The 

NMFS/NOAA schedule is from April 10 to June 20 at the Snake Rover projects and 

April 20 to June 30 at the lower Columbia River projects. Since the NMFS/NOAA 

Proposed Recovery Plan supersedes the fish and wildlife program, the NMFS/NOAA 

time periods are discussed below. 

The 1987 Fish and Wildlife Program set a standard of 90 percent fish guidance 

efficiency as a design criterion for intake screens. This standard was modified in the 

1994 Fish and Wildlife Program to specify "if it can be achieved." It is unlikely that this 

standard can be achieved with turbine intake screens for the mix of species present at any 

62
given project, as discussed in the text. The 1994 Fish and Wildlife Program set a 

standard of 98 percent survival to be achieved in bypass and collector facilities 

throughout the basin. This goal is probably achievable in properly operated and 

maintained systems 

NPPC Requirements for Spill 

The 1994 Fish and Wildlife Program established spill as an interim measure to 

produce 90 percent survival during the middle 80 percent of the spring and summer 

outmigrations at specified projects ".... until mechanical bypass systems are installed" 

(NPPC, 1994, p 5-25). Mechanical bypass systems are now in place at Wells Dam in the 

mid-Columbia Reach, and at all the Snake River and lower Columbia River projects 

except The Dalles Dam. 

In addition, the 1994 Fish and Wildlife Program calls for 80 percent fish passage 

efficiency at each Snake River project from April 15 to July 31 each year and at each 

Columbia River project (presumably lower Columbia) from May 1 to August 31. 

Because none of the bypass systems except Wells Dam can achieve 80 percent fish 

passage efficiency, spill is required to make up the difference between the fish guidance 

efficiency of the bypass systems in place and the 80 percent goal. 

The 1994 Fish and Wildlife Program refers to a 10-year “Spill Agreement”, 

reached in 1988 by the Mainstem Executive Committee. The committee consisted of 

representatives from BPA, the fishery agencies, tribes, and utility representatives. The 

agreement was developed in response to the Council’s call for coordinated interim fish 

passage plans in the 1984 Fish and Wildlife Program. The Corps agreed to adhere to the 

provisions of the agreement as these were described in the NPPC Amendments to the 

Fish and Wildlife Program for 1989, with some conditions. Levels of spill were specified 

for Lower Monumental, Ice Harbor, and The Dalles dams during spring and summer 

outmigration periods, and John Day dam during the summer, Table B.1. These are now 

superseded by the more stringent requirements of the Proposed Recovery Plan for 

Endangered Snake River Salmon to be described later (NMFS/NOAA, 1995). 

_______________________________________________________________________ 

Table B.1. Spill amounts specified in the Spill Agreement of 1989 for Corps Projects 

The agreement was somewhat complex. Among other things, it attempted to take load 

factoring into account in determining an appropriate percentage of flow to be spilled. 

(Source: Fish Passage Managers, 1990) 

Project Summer Spill Spring Spill 

Instantaneous Daily Average Instantaneous Daily Average 

Lower Monumental 70% 35% 70% 35% 

Ice Harbor 25% 12.4% 25% 12.5% 

The Dalles -- 10% -- 5% 

John Day -- 20% -- 8.3% 

63
NMFS/NOAA Recovery Plan Requirements for Mechanical Bypass and Spill 

Background 

Now and for the foreseeable future, the 1995 NMFS/NOAA Proposed Recovery 

Plan for Snake River Salmon is the governing factor in implementation of measures for 

survival of migrating juvenile salmon in the Snake River and lower Columbia River. It 

was developed because certain Snake River stocks of salmon were listed as threatened or 

endangered under the Endangered Species Act (NMFS/NOAA, 1995). Implementation 

of the provisions of the plan is accomplished primarily through the Technical 

Management Team composed of federal managers from NMFS, the U.S. Fish and 

Wildlife Service, the Bureau of Reclamation, BPA, and the Corps. 6

The NMFS/NOAA Proposed Recovery Plan, “... is based on the premise that 

there is sufficient uncertainty about the benefits of transportation to warrant an evaluation 

of whether improved inriver migration might result in as many (or more) returning adults 

than does the transportation program.” (NMFS/NOAA, 1995, p. V-2-50.) Accordingly, 

specific standards are established for inriver passage and a study is recommended to 

compare adult return rates from transported fish with return rates from inriver migrants 

that have had the benefit of improved inriver conditions. 

NMFS/NOAA, in their draft recovery plan for endangered Snake River salmon 

has established goals for passage applying to the projects in the Snake River and lower 

Columbia River. Because the bypass facilities that are in place on the Snake River and 

lower Columbia River do not guide enough fish to meet the 80 percent fish passage goal, 

spill must be provided in sufficient amounts to make up the difference. Calculation of 

the spill amount required at each project to achieve the NMFS/NOAA goal of 80 percent 

fish passage is not a simple matter, as will be explained below.

The NMFS/NOAA goal provides a refinement over the NPPC goal in the manner 

in which it distinguishes between the spring and summer migrations. The salmonid 

components of the migrations differ in spring and summer and the fish guidance 

efficiency for the components differ. This makes it is necessary to define fish guidance 

efficiency levels separately for spring and summer for each project.7

 The NMFS/NOAA 

goal, in practice, is more stringent than the NPPC goal, because NMFS/NOAA is 

 

6

 NMFS/NOAA has made a commitment to the Council to coordinate planning and implementation efforts, 

(Stelle, 1994). [Statement on actions necessary for the recovery of Snake River salmon presented to the 

NPPC by William Stelle, Jr., Northwest Regional Director, NMFS/NOAA on November, 1994. - Cited in 

Recovery Plan p.I-12.]

7

 The spill levels specified in the Proposed Recovery Plan (p. V-2-31 and 32) are not the levels actually 

used, as we explain later in the text. 

64
concerned with threatened or endangered species, which include sockeye and fall 

chinook that universally have shown low fish guidance efficiency. Spring/summer 

chinook, also threatened, show a higher fish guidance efficiency. Because fish guidance 

efficiency varies among the projects, the relative spill amounts required to achieve the 

standard also vary. 

With respect to spill requirements, the NMFS/NOAA Proposed Recovery Plan set 

limits on gas saturation at 115 percent in the forebay, on a 12 hour average, or 120 

percent in the tailrace for 12 hours. The Proposed Recovery Plan recognizes there are 

differences among projects in levels of gas saturation produced by given spill volumes, as 

well as an interaction between gas saturation levels at successive projects, and 

recommends studies to optimize spill levels within the limits set by gas saturation 

criteria. 

Part 2. Evaluation of Fish Passage Achieved in 1995 

Background 

 

At Wells Dam the decision to operate the bypass is made by a committee of 

representatives of the parties to the long-term settlement agreement, based upon 

information from hydroacoustic monitoring at the dam. At the other mid-Columbia 

projects the mid-Columbia Coordinating Committee and the Rock Island Coordinating 

Committee are given the responsibility of implementing the requirements. In particular, 

because the timing of outmigration differs from year to year, the committees have the 

responsibility of determining when the first 10 percent of the outmigration has appeared 

in order to commence the spill programs, for interrupting it if the data suggest it, and for 

terminating bypass operation and spill when appropriate. 

Achievement of FERC Requirements for Fish Passage and Spill in 1995 

Wells Dam 

In 1995, the bypass system at Wells Dam was operated on the agreed upon 

schedule. It is therefore reasonable to conclude that 89 percent of the juvenile salmonids 

were passed during the spring and summer migrations. 

Rocky Reach Dam 

Spill was provided at Rocky Reach Dam in the amounts specified for the spring 

and summer periods. Using the spill effectiveness curve developed for Rocky Reach 

Dam, an estimate of 10 percent fish passage can be obtained with 15 percent spill in 

spring and 6.6 percent fish passage with 10 percent spill in summer. 

Rock Island Dam 

The spill amount required can vary from day to day, because the formula in the 

FERC order depends upon the distribution of the load between the first and second 

65
powerhouses. The order requires spill of 10 percent of the flow volume through the 

second powerhouse and spill of 50 percent of the flow through the first powerhouse. In 

1995, spill amounted to 17 percent of the daily average flow in spring and 3.3 percent in 

summer. According to the spill effectiveness curve, an estimated 27 percent of the 

migrants were passed in spill in the spring and a small percentage in summer. These 

estimates do not take into account an estimated additional 5 to 10 percent of the migrants 

at the second powerhouse that enter the gatewells and are passed to the tailrace through 

the gatewell conduit. 

Wanapum and Priest Rapids Dams 

 

In 1995, based on past experience at Wanapum and Priest Rapids dams, the midColumbia Coordinating Committee agreed upon a schedule for a fixed number of days 

(35) of spill. The schedule included an option to apply for additional days if it appeared 

that 80 percent of migrating juvenile salmon had not yet passed the projects, as required 

by FERC. 

In 1994 and 1995, the committee found itself in a conflict at Wanapum and Priest 

Rapids dams between the FERC order to spill for fish passage and limits on spill because 

of water quality standards set by the Washington State Department of Ecology. The 

FERC order called for sufficient spill to achieve 70 percent fish passage during 80 

percent of the spring outmigration and 50 percent for the summer at Wanapum and Priest 

Rapids dams. This could not be achieved because of limits on gas supersaturation set in 

the special permit issued by the Washington Department of Ecology. The permit allowed 

Grant County Public Utility District to exceed the normal limit of 110 percent gas 

saturation in the river below the projects, but maintain it below 120 percent. In 1994, 

some exploratory manipulations of spill levels were required to comply with the limit on 

gas saturation. Spill of 17 percent of the daily average river flow for 24 hours a day for 

47 days was provided at Wanapum Dam in the spring and spill of 14 percent for 14 hours 

a day for 63 days was provided in the summer in 1995. At Priest Rapids Dam spill of 17 

percent for 24 hours a day for 47 days was provided in spring and spill of 14 percent for 

14 hours a day for 63 days was provided in the summer in 1995. 

The FERC requirement for 50 percent fish passage in the summer at Priest Rapids 

was achieved by spill at that project in 1995, when 62 percent of the fish were passed.

Failure to Achieve FERC Goals for Fish Passage in 1995 

at Wanapum and Priest Rapids Dams 

 Wanapum Dam did not achieve the FERC requirements of 70 percent fish passage 

in the spring and 50 percent in the summer. Fish passage was 52 percent in the spring 

and 25 percent in the summer. At Priest Rapids Dam, fish passage in the spring was 54 

percent, which did not meet the FERC requirement of 70 percent. The fish passage 

requirements were not reached, except at Priest Rapids in the summer, because spill was 

limited to avoid gas supersaturation. 

66
Failure to Achieve NPPC Goals or NMFS/NOAA 

Goals for Fish Passage in 1995 

Background 

Our discussion focuses on the question whether the NMFS/NOAA goals were 

achieved in 1995, as an example, or whether they are likely to be achieved in the future. 

We focus on the NMFS/NOAA goals because those goals are more stringent in one way 

than the NPPC goals. The NMFS/NOAA goals take into account differences in fish 

guidance efficiency between spring and summer. 

To attempt to achieve the NMFS goal of 80 percent fish passage, spill was 

required at the four lower Snake River dams from April 10 through June 20, and at the 

lower Columbia River dams from April 20 through June 30. The spill was to be in 

sufficient amounts to make up the difference between what could be accomplished with 

the fish guidance efficiency of the intake screens or sluiceways at the given project and 

the 80 percent goal, taking into account spill effectiveness at the project as well. 

(NMFS/NOAA, 1995 p. V-2-31.) The required spill amounts are larger than those in the 

10 year spill agreement that was reached according to NPPC requirements that were 

previously discussed and shown in Table B.1. The Proposed Recovery Plan set an upper 

limit on spill to be determined by dissolved gas concentrations. Spill was to be reduced 

at a project whenever a 12 hour average of total dissolved gas concentration exceeded 

115 percent in the forebay of any project or 120 percent at the tailrace. 

The Proposed Recovery Plan provided an exception during periods of low flow, 

during which there was to be no spill at certain projects in order to divert more fish into 

bypass systems where they could be transported by barge to below Bonneville Dam for 

release. The three lower Snake River projects, Lower Granite, Little Goose and Lower 

Monumental, were designated as “collector dams” where the focus was to be on 

transportation of smolts by barge as long as river flows remained below specified limits. 

Low flow was defined at Lower Granite Dam when the projected unregulated weekly 

average flow there is less than 100 kcfs or less than 85 kcfs. At flows from 85 kcfs to100 

kcfs no spill should occur at Lower Granite Dam. At flows less than 85 kcfs no spill 

should occur at Lower Granite, Little Goose or Lower Monumental dams. The Proposed 

Recovery Plan provides for exceptions if the Technical Management Team (TMT) so 

recommends. The team is made up of representatives of NMFS, Corps, BPA, Bureau of 

Reclamation, and the U.S. Fish and Wildlife Service. The plan also specifies that the 

team’s recommendations should consider the need for a credible evaluation. 

In 1995, flow at Lower Granite Dam was beneath the specified 85 kcfs in the 

period from April 10 to May 2 (FPC, 1995). Spill began at Lower Granite Dam on May 

3, 1995, when flow exceeded 100 kcfs, as provided for in the Proposed Recovery Plan. 

However, at Little Goose Dam spill began on April 14 and continued through May 2 at a 

level averaging 24.1 percent of the river flow during the period specified for no spill. At 

Lower Monumental Dam spill began on April 14 and continued through May 2, 

averaging 16 percent of the river flow during the time period specified for no spill (spill 

data courtesy of Fish Passage Center). Thus, in 1995, Little Goose and Lower 

Monumental dams were not operated as collector dams for transportation of juvenile 

salmonids, contrary to what is called for in the Proposed Recovery Plan. Probably, this 

67
was brought about by evaluations by the Technical Management Team of the flow 

forecast for Lower Granite Dam, rather than the actual flow. 

Specific Requirements for Spill 

Spill requirements, as applied by NMFS/NOAA, vary with the mix of yearling 

and subyearling chinook, steelhead, and sockeye, because the fish guidance efficiency 

varies among the species. Values for yearling chinook and steelhead are much higher 

than sockeye and subyearling chinook. A further complication is that yearling chinook 

and steelhead are early emigrants, with sockeye somewhat later, while subyearling 

chinook, though present through the season, predominate among the later emigrants (Fish 

Passage Center Annual Reports). For setting spill levels required to achieve the 80 

percent passage goal, the Proposed Recovery Plan uses two standard sets of fish guidance 

efficiency levels, one for spring and one for summer. These standards were adopted by 

NMFS/NOAA using what was judged to be the best available information (Detailed 

Fishery Operating Plan, 1993, according to FPAC, 1995), Table B.2. The fact that these 

"standard" values of fish guidance efficiency are higher in the spring period than in the 

summer might suggest that more spill would be required in the summer in order to 

achieve the 80 percent fish passage goal in summer. This refinement would lead to a 

situation that calls for more relative spill later in the season when water is in shortest 

supply. To circumvent this problem the Proposed Recovery Plan specifies that there 

should be no spill for summer migrants at Lower Granite, Little Goose, Lower 

Monumental, or McNary dams. The first three are named as the “collector dams”, as 

described above, where the emphasis is to be on collection of fish for transportation in 

the barges. The Proposed Recovery Plan also identifies a "spill cap" of 75 kcfs at 

Bonneville Dam to reduce adult fallback. 

________________________________________________________________________ 

Table B.2. Standard Fish Guidance Efficiency Used in 1995 by NMFS/NOAA to 

Calculate Spill Needed to Achieve 80 Percent Fish Passage. (Personal communication, 

Tom Berggren, Fish Passage Center). The values to be used for 1996 (shown in 

parentheses) will be somewhat higher in response to installation of extended screens at 

Lower Granite, Little Goose, Lower Monumental and McNary dams. (Source: Memo of 

Margaret Filardo, Fish Passage Center, to FPAC, January 18, 1996) 

Project: L. Granite L. Goose L. Monumental Ice Harbor 

4/10-6/20 .50 (.57) .56 (.63) .55 (.62) .73 

Summer .25 (..50) .25 (..50) .31(..54) .33 

 McNary J. Day The Dalles Bonn. (1 & 2) 

4/20-6/30 .70 .72 .43 .37 .44 

summer .47 (.58) .26 .43 .10 .40 

_____________________________________________________________________ 

As stated in the text, estimates of fish guidance efficiency have been found to differ from

project to project, and differ with other factors. These factors include the design and 

configuration of the apparatus, species, degree of smoltification, time of day (especially 

day vs. night), and the season. Therefore, we emphasize that the numbers for fish 

guidance efficiency shown in Table B.2. represent the judgment of those involved, and 

are not susceptible to duplication by purely technical analysis. 

68
Calculated Spill Amounts required in 1995 to Achieve 80 Percent Fish Passage 

 

As mentioned previously, the amount of spill required to bring fish passage 

efficiency up to the 80 percent level at individual projects depends upon several factors. 

These factors include whether or not the project is equipped with turbine intake screens, 

the fish guidance efficiency of the screens, the effectiveness of ice and trash sluiceways, 

and the effectiveness of spill in passing fish. In the absence of better information, 

calculation of the amount of spill required assumes a 1:1 relationship between the 

percentage of total river flow that is spilled and the percentage of fish that are passed in 

spill at each project. (See text for a critique of this assumption.) Spill levels calculated 

in this way, i.e. with the fish guidance efficiencies from Table B.2 judged to be the 

applicable ones, and with an assumption of a 1:1 spill effectiveness relationship, are 

those required to achieve the NMFS/NOAA bypass goals, Table B.3. 

The complexity of attempting to manage spill levels to attain a passage goal is 

illustrated in examples A and B in Table B.3. Method A is the simplest. It uses the fish 

guidance efficiency judged to be applicable over all species and conditions, as given in 

Table B.2. The estimation procedure is explained in the footnote in Table B.3. Method 

B depends upon the fish guidance efficiency judged to be applicable for each project and 

for each stock of chinook. Spill levels are determined for a 12 hour night period during 

which a higher percentage of fish are expected to pass and during which there is expected 

to be less demand for power. Method B then calculates what that total spill volume over 

12 hours would amount to relative to a 24 hour period of flow. Method B was used in 

The Detailed Fishery Operating Plan of the Agencies and Tribes (Detailed Operating 

Fishery Plan, 1993). 

To determine how much spill should be required to achieve the goals by Method 

A, we needed to assume a 1:1 relationship of percentage of river flow spilled to the 

percentage of fish passage, except at John Day and The Dalles, where specific 

information is available. (See text, and Magne, et al. 1987, and Willis, 1982.) Sluiceway 

passage, where present, is included within the 80 percent passage. Sluiceway passage at 

Bonneville Dam is not included. More information is needed there. Method B assumes a 

1:1 relationship at all projects. 

_______________________________________________________________________

Table B.3. Spill Amounts (As a Percentage of Total River Flow) Calculated to be 

Required for 80% Fish Passage 

 Method A. Method B. Numbers from DFOP (1993) 

69
 Spring Summer Spring Chinook Fall Chinook 

 (Summer Migrants)

 Project Spill (%) Spill (%) Spill (%) Spill (%) 

Lower Granite 60 73 39 49.5 

Little Goose 54 73 24 49.5 

Lower Monumental 56 71 27 50 

Ice Harbor 26 70 47 47 

McNary 33 62 24 45 

John Day 36* 73* 17.5 42 

The Dalles 31* 31* 40 40 

Bonneville I 68 77 68 77 

Bonneville II 64 67 (powerhouse should not 

 operate)

* For John Day and The Dalles dams, spill effectiveness curves were used in method A. 

They differ from the 1:1 relationship assumed for the other projects and for method B. 

**Spill percentages required for Method A were calculated from the equation 

0.8N = NX + (FGE)(N-NX), where N is the number of downstream migrants, and X is 

the spill percentage required to provide 80 percent fish passage. Percentages for John 

Day and The Dalles were adjusted according to their spill effectiveness curves. 

 ***If mortality rates of 2 percent in spill and 2 percent in bypass systems are assumed, 

along with an assumed 11 percent mortality in turbines, the total survival at each project, 

with 80 percent fish passage would be a little over 95 percent. 

****The spill amounts that will be required in 1996 to achieve the 80 percent passage 

goal, with new extended screens in place, have been calculated by Margaret Filardo, Fish 

Passage Center. Generally, they are less than in 1995 by about 10 percent. (Memo of 

January 18, 1996 to FPAC). 

________________________________________________________________________ 

Discussion 

The primary point that emerges from Table B.2 is that there can be considerable 

difference in the calculations of the amount of spill required to supplement the bypass 

system to achieve 80 percent fish passage at particular projects. Method A estimated 

spill amounts required to achieve the 80 percent fish passage that were higher than 

method B at most of the projects, but lower at Ice Harbor and The Dalles dams. The 

lower estimate of spill amount required at Ice Harbor Dam in the spring using method A 

results from the high fish guidance efficiency value in the table. The lower estimate for 

spill with method A at The Dalles is due to use of the spill effectiveness curve, rather 

than the 1:1 assumption. Spill required at John Day is higher in method A because spill 

effectiveness there is less than 1:1. The spill estimates for Bonneville Dam are the same

by both methods. Whether or not they would fall within the 75 kcfs cap on spill set at 

Bonneville by NMFS/NOAA would depend upon river flow. 

The differences between methods A and B arise because of 1) differences in the 

assumption regarding spill effectiveness and effectiveness of the ice and trash 

sluiceways, 2) differences in adjustments of fish guidance efficiency made on the basis of 

a judgment as to the mix of stocks expected at each project, and 3) differences brought 

about by adjusting 12 hour night-time spill over a 24 hour period. Calculation of spill 

70
amounts is sensitive to information on spill effectiveness, and this information is not 

sufficient at most of the Corps projects to warrant the assumption of a 1:1 relationship. 

The judgment as to an appropriate adjustment of fish guidance efficiency requires 

predictions of all of those factors we pointed out in the text that can affect measurement 

of fish guidance efficiency. These factors include the performance of the bypass at the 

particular project, stock of fish, size of fish, degree of smoltification, time of day, and 

progress of the season. While it appears to be unlikely that estimates independently 

arrived at would coincide, the process used is a group analysis where collective judgment 

enters in and appears to be satisfactory to the participants. 

Our analysis of diel passage in the text suggests both methods probably 

overestimate the amount of spill required as a percentage of river flow, for two reasons. 

First, spill over a 24 hour period may be nearly twice as effective as spill of the same

water volume for 12 hours (based on data at Wanapum and Priest Rapids dams). Second, 

if surface spill is provided, it is likely that fish passage efficiency can be further 

increased. Further studies are needed. 

Failure to Achieve Goals in the NMFS/NOAA Proposed Recovery Plan 

Background 

Achievement of fish passage goals can now be evaluated by comparing the spill 

levels actually provided with the spill levels specified in Table B.3. Method B is used 

here so as to be able to use the estimates of fish passage calculated by the Fish Passage 

Center (1995). At most of the projects in 1995, spill levels could not be increased 

enough to meet the 80 percent passage goal, in spite of the provision allowing gas 

saturation levels to 120 percent. This was true even though by 1995, five of the eight 

federal mainstem and Snake River projects were at least partially equipped with flip-lip 

spillway deflectors. See Appendix A, Table A.1. 

Ice Harbor Dam was the one Corps’ project where the 80 percent fish passage 

goal was achieved in 1995, when outages of units led to forced spill and gas saturation 

that exceeded the permitted limits. Fish passage goals were not attained elsewhere in the 

Snake River or lower Columbia River (Fish Passage Center, 1995). 

Evaluation of Fish Passage Goals at Each Project 

Introduction 

From late May into June 1995 Snake River runoff could not be regulated within 

lower levels. Flows at Lower Granite, Little Goose and Lower Monumental dams

exceeded powerhouse capacities. Consequently, there was “inadvertent spill” that 

contributed toward the goal of attaining 80 percent passage efficiency but led to 

exceeding the gas saturation limits (Fish Passage Center, 1995). The 115 percent 

criterion in the Proposed Recovery Plan was exceeded during half or more of the spill 

period specified in the plan. From April 10 to June 20, the criterion was exceeded at 

three of the four Snake River projects, Little Goose, Lower Monumental and Ice Harbor 

dams. For most of the April 20 to June 30 spill period, the criterion was exceeded at 

three of the four lower river projects, McNary, John Day, and Bonneville dams. The 120 

percent criterion was also exceeded for several days at Little Goose Dam, about 10 days 

71
at Lower Monumental, about 3 weeks at Ice Harbor Dam, for several days at McNary 

Dam, and intermittently over the spill period at John Day Dam. 

The Fish Passage Center provided spill data for the following description of

operations at each project. Estimates of fish passage appear in Fish Passage Center 

(1995). 

Snake River Projects 

Lower Granite Dam 

Spill at Lower Granite Dam began on May 3, when flow exceeded 100 kcfs as provided 

in the Plan, and extended through June 20, 1995. Spill amounted to 14.6 percent of the 

daily average flow. An estimated 50 to 56 percent of the fish were successfully passed 

through a combination of bypass facilities and spill. 

Little Goose Dam 

Spill began at Little Goose Dam on April 14 and extended to June 30, 1995 at 21.7 

percent of the daily average flow. An estimated 60 percent of the fish were passed in the 

combination of bypass facilities and spill. 

Lower Monumental Dam 

Spill began at Lower Monumental Dam on April 14 and continued through June 28. 

Spill amounted to 16.6 percent of the daily average flow. The combination of bypass 

operation and spill passed an estimated 58 to 60 percent of the fish. 

Ice Harbor Dam. 

At Ice Harbor Dam, the volume of spill observed during the interval specified in the 

NMFS Proposed Recovery Plan amounted to 35.9 percent of the daily average flow, 

which exceeded the 26 percent calculated to meet the 80 percent passage goal. (Data 

from Fish Passage Center, 1995.) Gas saturation levels of 130 to 138 percent were 

recorded from May 25 to June 8 in the tailrace. The 115 percent criterion was exceeded 

during most of the days between April 20 and June 30. An estimated 79 to 84 percent of 

the fish were passed in the combination of turbine intake bypass and spill. 

Lower Columbia River Projects 

McNary Dam 

Spill intended for fish passage began at McNary Dam on April 20 and extended through 

June 30, 1995. There was inadvertent spill prior to April 20, 1995 when river flows 

exceeded plant capacity. Spill amounted to 39.8 percent of the daily average flow in the 

interval from April 20 to June 30, 1995. Through a combination of bypass operation and 

spill an estimated 73 to 77 percent of the fish were successfully passed. 

John Day Dam 

Spill began on April 25 and extended through June 30, 1995 at a level of 3.8 percent of 

the daily average flow. Through combinations of the intake bypass system and spill an 

estimated 72 to 72 percent of the fish were passed. 

The Dalles Dam

Spill for fish began on April 20 and extended through June 30, 1995. Spill averaged 57.2 

percent of the daily average flow in that interval. An estimated 78 percent of the fish 

were successfully pass through combinations of the ice and trash sluiceway and spill. 

Bonneville Dam

72
Inadvertent spill occurred from April 14 to 19, 1995. Spill for fish began on April 20 and 

continued through June 30, 1995. Spill amounted to 34.5 percent of the daily average 

flow during that period. Through combinations of bypass and spill an estimated 55 to 62 

percent of the fish were passed. 

SUMMARY 

1. With respect to the NMFS/NOAA requirements, that apply in the Snake River 

and lower Columbia River, fish passage efficiencies achieved at projects other than Ice 

Harbor Dam were below the 80 percent called for in the Proposed Recovery Plan (Fish 

Passage Center, 1995). 

2. Under the NMFS/NOAA requirements, highest fish passage, 78 percent, was 

achieved at The Dalles Dam. All of the lower river projects achieved fish passages in the 

70 percent range, with the exception of Bonneville Dam at 55 to 62 percent. Snake River 

projects achieved fish passages in the 50 to 60 percent range, with the exception of Ice 

Harbor Dam, where there was excessive spill due to outages of turbines. 

3. As long as limits on gas saturation restrict the volume of spill permitted at 

Snake River or Columbia River projects, spill cannot be used either alone or as a 

supplement to intake screens at levels required to achieve fish passage goals established 

either by FERC, the NPPC, or NMFS/NOAA at any of the 13 projects on the Snake 

River or Columbia River Mainstem. Exceptions include Wells Dam (no spill required) 

in both spring and summer, Priest Rapids Dam (spill alone) in the summer, and perhaps 

The Dalles (ice and trash sluiceway and spill) in spring. The flip-lip spillways that are in 

place at some of the Corps projects are not effective enough to circumvent the problem of 

gas supersaturation 

4. The upper limit of 115 percent gas saturation, specified in the NMFS/NOAA 

Proposed Recovery Plan, can not be adhered to during normal spring runoff. 

5. The calculated spill amounts in the Detailed Fishery Operating Plan depend 

upon an assumption (or conclusion) that there is an advantage to spilling 12 hours at 

night versus 24 hours a day as a benefit to power production. Our review suggests that it 

would be worthwhile to conduct a more detailed examination of fish passage data related 

to duration of spill and of surface spill versus standard spill. This examination would 

include analysis of costs and benefits to the power system in various scenarios of spill 

duration. The goal of the examination would be to find an optimum strategy for fish and 

power. Spill of a given volume of water (in acre feet) at Grant County Public Utility 

District projects was found to be twice as effective in providing fish passage when spread 

over a 24 hour period as when the same number of acre feet was used over a 12 hour 

period. 

6. Spill effectiveness curves are needed for the Corps’ projects, in order to 

calculate the spill amounts needed to achieve the 80 percent fish passage goal. Current 

practice of assuming a 1:1 relationship between percentage of the river spilled and 

percentage of fish passed could lead to significant error. At John Day Dam, the effect 

would amount to a difference in fish passage of about 10 percent less fish passage at spill 

levels around 50 percent of river flow. At The Dalles Dam, where spill is more effective, 

20 percent spill gives about 50 percent fish passage (Willis, 1982). 

73
DISCUSSION 

At the so-called collector dams, Lower Granite, Little Goose and Lower 

Monumental dams, the 80 percent fish passage goal in 1995 presumably applied after 

May 3 when flows exceeded 100 kcfs. At Lower Granite Dam, if we consider that 49 

days remained out of the total 68 day period, then the estimated 50 to 60 percent fish 

passage over the season might be considered to represent perhaps 76 percent fish passage 

during the time when flows exceeded 100 kcfs and the dam was operated for in-river 

passage. On the other hand, the early starts of spill at Little Goose and Lower 

Monumental Dams, where only four days were without spill, would lead to negligible 

adjustments in the estimates of fish passage (58 to 60 percent) at those projects. 

In years when river flow exceeds generating capacities at the Snake River projects 

(780,000 kilowatts at Ice Harbor and 930,000 kilowatts at the others), or plant capacity is 

reduced due to outages of turbines, there will be inadvertent spill which at some point 

will reach levels sufficient to achieve the fish passage goals. However, this will be at the 

expense of juvenile salmonid mortality caused by gas supersaturation. There is a need 

for more information on this subject. 

Although laboratory studies and studies of captive fish held in the river would 

have predicted juvenile salmon loss caused by high gas saturation levels measured in the 

Snake River, recoveries of PIT-tagged smolts led to estimates of survival from the 

tailrace at Lower Monumental Dam to the McNary Dam tailrace. These survival 

estimates were 84 percent from April 27 to May 10, 98 percent in the interval from May 

11 to May 24, and 100 percent in the interval from May 25 to June 11 (Fish Passage 

Center, 1995). At Ice Harbor Dam, during those three periods, average daily spill was 

35.1, 38.2 and 43.5 percent of the flow. At McNary Dam spill was 39.6, 44.3 and 43.0 

percent of river flow. Gas saturation levels were above 120 percent for three of those 

weeks at Ice Harbor Dam, for several days at Little Goose Dam, 10 days at Lower 

Monumental Dam, and for several days at McNary Dam, as described above. (Fish 

Passage Center, 1995). Contrary to expectations the survival of smolts in this river reach 

was high and did not decrease as the percentage of spill increased. 

The NMFS/NOAA Proposed Recovery Plan states that the spill program it 

specifies is experimental. The Proposed Recovery Plan also calls for study of gas saturation. In view of the Fish Passage Center analysis showing high survival of smolts from

Lower Granite to McNary Dam during high spill episodes in the Snake River in 1995, we 

believe further consideration of the limits are in order. Specifically, a study should be 

designed that measures survival of smolts from upper river to lower river projects under 

varying volumes of spill relative to river flow. The study could be like the Fish Passage 

Center study that used data available from the NMFS Snake River survival study. 

NMFS/NOAA requirements for spill are founded upon a conclusion that the rate 

of survival of juvenile salmonids in spill is 98 percent. (Personal communication, Tom

Berggren, FPC.) If the 80 percent fish passage goal is achieved, survival at each of the 

projects would probably be about 95 percent. If 90 percent survival were taken as the 

primary criterion, rather than 80 percent fish passage efficiency, then less spill would be 

required. As an example, we can calculate the mortality at McNary Dam for an 80 

percent fish passage goal using 33 percent spill as was previously used. Additional 

assumptions include 11 percent mortality of smolts in turbines, 2 percent mortality in the 

bypass, 2 percent mortality in spill and 70 percent fish guidance efficiency for the spring. 

74
Then mortality at the project would be estimated as 2.2 percent in the turbines, (0.70 X 

0.67 = 0.469; 0.67 - 0.469 = 0.201; 0.201 X 0.11 = 0.022): perhaps 0.6 percent in spill, 

(0.33 X 0.02 = 0.006), and 0.9 percent in the bypass (0.469 X 0.02 = 0.009), for a total of 

3.7 percent mortality at the project. The 90 percent survival criterion of NMFS/NOAA 

would thus be exceeded by means of the 80 percent fish passage criterion. However, this 

estimate does not include mortality in the reservoir. 

75
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