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Dams and river regulation in the columbia basin-deadly to U.S. anadromous fish resource
News and Notices DAMS
AND
RIVER
R E G U L A T I O N IN THE COLUMBIA B A S I N - - D E A D L Y A N A D R O M O U S FISH R E S O U R C E
49 TO
U.S.
B~ogE the dams, juvenile chinook salmon and steelhead trout migrated down the Snake and Columbia Rivers to the ocean in spring and early summer under naturally ideal conditions. The water flow was high, water temperatures were favorable, turbidity was sufficient for protection from predators, and there were no large impoundments with slow-moving water to cause delay during the trip to the sea. This environment has been changed drastically in recent years. What once was a comparatively rapid flow of water is now a series of dams and reservoirs. Fingerlings on their journey to the ocean are subject to high mortality from passing through turbines at dams, predation in tailraces below the dams and in the reservoirs, and nitrogen supersaturation resulting from spilling at dams. In addition, delay in migration results from reduced water velocities caused by regulation of river runoff and impoundments. Young migrants from the Salmon River (a principal spawning tributary of the Snake River) must pass through eight large impoundments and over eight major dams to reach the sea. Even small losses or delays at each dam become serious because of the large number of dams. An examination of data on adult returns only would indicate no serious decline in the chinook salmon and steelhead trout runs of the Snake River before 1974. However, adult returns have been declining at increasing rates since new dams were constructed in the Snake River starting in 1969. Fingerlings of these species released from hatcheries in greatly increased numbers since 1970 have generally offset losses to downstream migrants in most years. However, significant mortalities of juveniles caused by adverse downstream passage conditions in 1972 and 1973 could not be offset by hatchery releases, and returns in 1974 and 1975 from these outmigrations were extremely low. The deteriorating conditions for fish passage downriver in recent years are reflected by the low percentage of adult fish returning to the Snake River from known populations of juvenile chinook salmon and steelhead trout starting their downstream migrations. Adult return percentages have decreased from a level of 4-6~o prior to new dams to about 0.3 ~ in 1973 when low runoff forced nearly the entire juvenile outmigration through the powerhouses of seven dams and significantly slowed water velocities through the reservoirs. During that year, 95 ~o of the juveniles were killed, and migrations of juveniles between Little Goose and The Dalles Dams were delayed 30 days. Howard L. Raymond and other scientists of the U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA) in cooperation with, and supported substantially by the U.S. Army Corps of Engineers, are concerned that turbine-predator related mortalities experienced in 1973 will occur with greater frequency after 1979 when 15 new turbines will have been installed in dams on the lower Snake River. Working in NOAA's National Marine Fisheries Service, Northwest Fisheries Center, in Seattle, Washington, they recently reported* that critical losses that in the past occurred only during low-flow years are also be expected during average-flow years after 1979. Therefore, only a few years are available to develop and refine solutions to fish passage problems. Fortunately their research has already pointed the way to several important steps to minimize losses of salmon and steelhead due to dams. If applied soon, these methods can probably save this valuable resource. Reduction of nitrogen supersaturation has been essentially achieved through installation of spillway flow deflectors at Bonneville, McNary, Lower Monumental, Little Goose, and Lower Granite Dams. Research has shown that the deflectors have substantially reduced the nitrogen supersaturation, and they have not injured or had any adverse effects on either adults or juveniles. One practical way to reduce losses of migrating juvenile salmon and steelhead trout is to collect them at upriver dams and transport them in tanker trucks around the intermediate dams to the estuary. Data from steelhead transported in 1973 show that they contributed substantially to the returns. A total of I 1,000 adults returned in the 1974--75 runs. The transport contribution was 4345, or about 40 ~o of the total returns even though only 3.5 ~o of the downstream migrants were transported. Collection and transportation is not only a practical solution in preventing turbine-predator related mortality and delay in passing through the reservoirs, but the cost-benefit ratio is acceptable. Another approach is to install screens in the turbine intakes of the dams and bypass the downstream migrants around the turbines. The process is costly; and migration delay, predation, and disease in reservoirs would still exist. Furthermore, many bypasses are inefficient, and some bypass exits are located where predators gather. Losses due to bypass inefficiency and predators may offset the advantages of screening and bypassing. Bypass systems need to be evaluated on a dam-by-dam basis before recommending their use. Flow control (use of upstream storage) is yet another method for reducing adverse conditions at dams and delays through reservoirs. By the manipulation of river flows during peak periods of juvenile out*Raymond, Howard L., "Effect of Dams and River Regulation on Runs of Anadromous Fish to the Mid-Columbia and Snake Rivers," in Proceedings of the Symposium and Speciality Conference on Instream Flow Needs, sponsored by the Western Division, American Fisheries Society and the American Society of Civil Engineers, Power Division, Boise, Idaho, May 3-6, 1976, Vol. 2, pp. 444-465.
50
News and Notices F .......
~ .......................................................... Canada
[
Columbia Chief River
Wash Wells
Rock~ y Reach I ~
Rock Island ~ "
Wanapum -~-
'
Grand Coulee Little
G....
i
t[
Idaho
I
j
Priest Rap{ds~I~..~ / , ~ L . . . . G. . . . t. The onulnental Oolles ~ T C e L°r:eorrMc\ ,,.~Sa I m o n
~
Oregon
~
OXbo~ Brownlee
, river
.......C~f ~'--
[
Main stem dams in the
Nevada
columbia river basin
Fie. 1. The construction of many large dams on the Columbia and Snake Rivers system has impounded most of the free-flowing sections of these rivers and created water conditions that in both high- and low-flow years are deadly to migrating salmon. With high spills, water becomes supersaturated with nitrogen to levels that are lethal to fish. In low flows, with no spill, all downstream migrants must pass through turbines where many are killed outright and others are injured or stunned and left vulnerable to intensive predation. The size of the adult fish runs has already been drastically reduced. Continued development of the river could destroy these valuable runs of anadromous fish. Corrective action to reduce some of the major hazards, if taken promptly, may save this valuable resource. The illustration shows locations of major dams that contribute to the problems. migration, sufficient water could be provided to minimize delay and provide enough spill to reduce turbine mortality at dams. However, users of water for power and irrigation are competing for the same water and their demands are increasing each year. Priorities for use of this valuable water need to be established. Research is in progress to better define how much spill and river flow is needed to maximize survival of juveniles. Steelhead are used to illustrate the scale of the benefit anticpated as a result of installation of spillway deflectors and full-scale transportation of juveniles from collector dams on the Snake River. Adult returns are predicted to increase from the low of 11,000 fish returning from the extremely reduced 1973 outmigration to an average of 127,000 fish (assuming six turbine units are screened at Lower Granite and Little Goose Dams). It is estimated that an additional production of 2 million smelts in hatcheries coupled with these remedial actions would add 55,000 to the run for a total of 182,000 fish. Without the proposed measures, only 12,000 adults would be produced from the hatchery releases. Fisheries scientists believe that the spawning returns of chinook salmon and steelhead trout can be greatly increased if the already developed and proven techniques for ensuring the increased outmigration of juveniles are successfully applied to the dams in the Columbia-Snake Rivers system.
News and Notices Snake 1401
r~/ef
Adult
chinook
51
run
Snake
run
river Adult
120[-
steelheod
runs
run
80
60 =I
6O
40--esttrnafed c a t c h of 20 S n a k e r i v e r chtnook in ~: - - l o w e r river f i s h e r y #--
06
J 68
Estimated
70 ¢2 Y e a r of a d u l t
40 20
i 74 return
i 76
chinook smolt count a t upper d a m
0
....
66
Estimated
I
68
72 74 Year of a d u l t r e t u r n 70
I 76
steelheod smolt count at upper d a m
5-
Ist release pahslrneroi hatcher 3 -
4
2 -
Ist r e l e a s e
from
I 6'6 Year Adutt return
68 70 72 of o u t m i q r a t i o n
as p e r c e n t a g e
of s m o l t c o u n t
,! "
o I
74
64
Adult
;
I
66 68 70 ~'2 Year of o u t m i g r a t i o n return
as p e r c e n t a g e
L 74
of s m o l t count
g
i
0.8% 64
Year
of o u t m i g r a t i o n
66
68
70
72
74
Year of o u t m i g r a t i o n
Fie. 2. Largedams on the Columbia-Snake River system have drastically reduced the numbers of juvenile chinook and stcelhead trout surviving the migration from headwater streams to the sea. As a consequence, increasingly smaller numbers of adult fish return to the spawning streams some 2-3 years later. Delays in passage through reservoirs, and fish losses due to turbines, predation, and lethal levels of atmospheric gas saturation are factors in the destruction of a large percentage of the total outmigrants. The illustration shows that for the period 1964 to 1974-75, despite generally increasing numbers of juvenile chinook salmon and steelhead trout available for the downstream migration (middle charts), the number of returning adults has declined significantly in recent years (upper charts). The adult returns as a percentage of the smolt counts during the period (lower charts) has dropped from 4-6 % before new dams to 0.2-0.3 %--almost to the vanishing point--since three new dams were completed on the Snake River.
AND
RIVER
R E G U L A T I O N IN THE COLUMBIA B A S I N - - D E A D L Y A N A D R O M O U S FISH R E S O U R C E
49 TO
U.S.
B~ogE the dams, juvenile chinook salmon and steelhead trout migrated down the Snake and Columbia Rivers to the ocean in spring and early summer under naturally ideal conditions. The water flow was high, water temperatures were favorable, turbidity was sufficient for protection from predators, and there were no large impoundments with slow-moving water to cause delay during the trip to the sea. This environment has been changed drastically in recent years. What once was a comparatively rapid flow of water is now a series of dams and reservoirs. Fingerlings on their journey to the ocean are subject to high mortality from passing through turbines at dams, predation in tailraces below the dams and in the reservoirs, and nitrogen supersaturation resulting from spilling at dams. In addition, delay in migration results from reduced water velocities caused by regulation of river runoff and impoundments. Young migrants from the Salmon River (a principal spawning tributary of the Snake River) must pass through eight large impoundments and over eight major dams to reach the sea. Even small losses or delays at each dam become serious because of the large number of dams. An examination of data on adult returns only would indicate no serious decline in the chinook salmon and steelhead trout runs of the Snake River before 1974. However, adult returns have been declining at increasing rates since new dams were constructed in the Snake River starting in 1969. Fingerlings of these species released from hatcheries in greatly increased numbers since 1970 have generally offset losses to downstream migrants in most years. However, significant mortalities of juveniles caused by adverse downstream passage conditions in 1972 and 1973 could not be offset by hatchery releases, and returns in 1974 and 1975 from these outmigrations were extremely low. The deteriorating conditions for fish passage downriver in recent years are reflected by the low percentage of adult fish returning to the Snake River from known populations of juvenile chinook salmon and steelhead trout starting their downstream migrations. Adult return percentages have decreased from a level of 4-6~o prior to new dams to about 0.3 ~ in 1973 when low runoff forced nearly the entire juvenile outmigration through the powerhouses of seven dams and significantly slowed water velocities through the reservoirs. During that year, 95 ~o of the juveniles were killed, and migrations of juveniles between Little Goose and The Dalles Dams were delayed 30 days. Howard L. Raymond and other scientists of the U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA) in cooperation with, and supported substantially by the U.S. Army Corps of Engineers, are concerned that turbine-predator related mortalities experienced in 1973 will occur with greater frequency after 1979 when 15 new turbines will have been installed in dams on the lower Snake River. Working in NOAA's National Marine Fisheries Service, Northwest Fisheries Center, in Seattle, Washington, they recently reported* that critical losses that in the past occurred only during low-flow years are also be expected during average-flow years after 1979. Therefore, only a few years are available to develop and refine solutions to fish passage problems. Fortunately their research has already pointed the way to several important steps to minimize losses of salmon and steelhead due to dams. If applied soon, these methods can probably save this valuable resource. Reduction of nitrogen supersaturation has been essentially achieved through installation of spillway flow deflectors at Bonneville, McNary, Lower Monumental, Little Goose, and Lower Granite Dams. Research has shown that the deflectors have substantially reduced the nitrogen supersaturation, and they have not injured or had any adverse effects on either adults or juveniles. One practical way to reduce losses of migrating juvenile salmon and steelhead trout is to collect them at upriver dams and transport them in tanker trucks around the intermediate dams to the estuary. Data from steelhead transported in 1973 show that they contributed substantially to the returns. A total of I 1,000 adults returned in the 1974--75 runs. The transport contribution was 4345, or about 40 ~o of the total returns even though only 3.5 ~o of the downstream migrants were transported. Collection and transportation is not only a practical solution in preventing turbine-predator related mortality and delay in passing through the reservoirs, but the cost-benefit ratio is acceptable. Another approach is to install screens in the turbine intakes of the dams and bypass the downstream migrants around the turbines. The process is costly; and migration delay, predation, and disease in reservoirs would still exist. Furthermore, many bypasses are inefficient, and some bypass exits are located where predators gather. Losses due to bypass inefficiency and predators may offset the advantages of screening and bypassing. Bypass systems need to be evaluated on a dam-by-dam basis before recommending their use. Flow control (use of upstream storage) is yet another method for reducing adverse conditions at dams and delays through reservoirs. By the manipulation of river flows during peak periods of juvenile out*Raymond, Howard L., "Effect of Dams and River Regulation on Runs of Anadromous Fish to the Mid-Columbia and Snake Rivers," in Proceedings of the Symposium and Speciality Conference on Instream Flow Needs, sponsored by the Western Division, American Fisheries Society and the American Society of Civil Engineers, Power Division, Boise, Idaho, May 3-6, 1976, Vol. 2, pp. 444-465.
50
News and Notices F .......
~ .......................................................... Canada
[
Columbia Chief River
Wash Wells
Rock~ y Reach I ~
Rock Island ~ "
Wanapum -~-
'
Grand Coulee Little
G....
i
t[
Idaho
I
j
Priest Rap{ds~I~..~ / , ~ L . . . . G. . . . t. The onulnental Oolles ~ T C e L°r:eorrMc\ ,,.~Sa I m o n
~
Oregon
~
OXbo~ Brownlee
, river
.......C~f ~'--
[
Main stem dams in the
Nevada
columbia river basin
Fie. 1. The construction of many large dams on the Columbia and Snake Rivers system has impounded most of the free-flowing sections of these rivers and created water conditions that in both high- and low-flow years are deadly to migrating salmon. With high spills, water becomes supersaturated with nitrogen to levels that are lethal to fish. In low flows, with no spill, all downstream migrants must pass through turbines where many are killed outright and others are injured or stunned and left vulnerable to intensive predation. The size of the adult fish runs has already been drastically reduced. Continued development of the river could destroy these valuable runs of anadromous fish. Corrective action to reduce some of the major hazards, if taken promptly, may save this valuable resource. The illustration shows locations of major dams that contribute to the problems. migration, sufficient water could be provided to minimize delay and provide enough spill to reduce turbine mortality at dams. However, users of water for power and irrigation are competing for the same water and their demands are increasing each year. Priorities for use of this valuable water need to be established. Research is in progress to better define how much spill and river flow is needed to maximize survival of juveniles. Steelhead are used to illustrate the scale of the benefit anticpated as a result of installation of spillway deflectors and full-scale transportation of juveniles from collector dams on the Snake River. Adult returns are predicted to increase from the low of 11,000 fish returning from the extremely reduced 1973 outmigration to an average of 127,000 fish (assuming six turbine units are screened at Lower Granite and Little Goose Dams). It is estimated that an additional production of 2 million smelts in hatcheries coupled with these remedial actions would add 55,000 to the run for a total of 182,000 fish. Without the proposed measures, only 12,000 adults would be produced from the hatchery releases. Fisheries scientists believe that the spawning returns of chinook salmon and steelhead trout can be greatly increased if the already developed and proven techniques for ensuring the increased outmigration of juveniles are successfully applied to the dams in the Columbia-Snake Rivers system.
News and Notices Snake 1401
r~/ef
Adult
chinook
51
run
Snake
run
river Adult
120[-
steelheod
runs
run
80
60 =I
6O
40--esttrnafed c a t c h of 20 S n a k e r i v e r chtnook in ~: - - l o w e r river f i s h e r y #--
06
J 68
Estimated
70 ¢2 Y e a r of a d u l t
40 20
i 74 return
i 76
chinook smolt count a t upper d a m
0
....
66
Estimated
I
68
72 74 Year of a d u l t r e t u r n 70
I 76
steelheod smolt count at upper d a m
5-
Ist release pahslrneroi hatcher 3 -
4
2 -
Ist r e l e a s e
from
I 6'6 Year Adutt return
68 70 72 of o u t m i q r a t i o n
as p e r c e n t a g e
of s m o l t c o u n t
,! "
o I
74
64
Adult
;
I
66 68 70 ~'2 Year of o u t m i g r a t i o n return
as p e r c e n t a g e
L 74
of s m o l t count
g
i
0.8% 64
Year
of o u t m i g r a t i o n
66
68
70
72
74
Year of o u t m i g r a t i o n
Fie. 2. Largedams on the Columbia-Snake River system have drastically reduced the numbers of juvenile chinook and stcelhead trout surviving the migration from headwater streams to the sea. As a consequence, increasingly smaller numbers of adult fish return to the spawning streams some 2-3 years later. Delays in passage through reservoirs, and fish losses due to turbines, predation, and lethal levels of atmospheric gas saturation are factors in the destruction of a large percentage of the total outmigrants. The illustration shows that for the period 1964 to 1974-75, despite generally increasing numbers of juvenile chinook salmon and steelhead trout available for the downstream migration (middle charts), the number of returning adults has declined significantly in recent years (upper charts). The adult returns as a percentage of the smolt counts during the period (lower charts) has dropped from 4-6 % before new dams to 0.2-0.3 %--almost to the vanishing point--since three new dams were completed on the Snake River.