Managing the Columbia River Instream Flows, Water Withdrawals, and Salmon Survival (2004) / Chapter Skim
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4 Environmental Influences on Salmon
4 Environmental Influences on Salmon
Pages 71-106
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From page 71... ...
In addition to the biological complexities of salmon species, within the impounded Columbia River they have been affected by an array of environmental conditions and changes, such as in creasing water temperatures and changes to other water quality parameters, changes to water velocity through reservoirs, habitat degradation, changing turbidity, shifting seasonal patterns and volumes of river flows, passage effects at dams, and changes in predators and predation rates. Scientists and water managers have considered these issues when formulating fish passage strategies such as flow augmentation, construction of smolt (young salmon, generally two to three years in age)
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From page 72... ...
COLUMBIA RIVER SALMON Three species of anadromous salmonids commonly migrate through the middle and upper reaches (above Bonneville Dam) of the Columbia and Snake rivers in the State of Washington: Chinook (Oncorhynchus tshawytscha)
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From page 73... ...
Summer Chinook salmon, which use the Columbia River upstream from the mouth of the Snake River, enter the river mostly in May and June and spawn in Sep tember and early October in natal streams such as the Wenatchee
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From page 74... ...
most important spawning area -- a long, damless stretch of river known as "The Hanford Reach" -- lies between Priest Rapids Dam and the head of McNary Dam pool. The shoreline-oriented behavior of subyearling fall Chinook salmon in flowing river segments, and their relatively slow rear ing migration in the Snake and Columbia rivers, which occurs in early and midsummer, makes them potentially vulnerable to high water temperatures.
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From page 75... ...
and virtually all suitable streams upstream from Bonneville, enter the Columbia River from May to early September. Adults spend the winter in the mainstem of the Co lumbia and Snake rivers and in large tributaries and spawn mostly in the period from March to May.
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From page 76... ...
; 6. Snake River fall Chinook (adults)
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From page 77... ...
900000 Bonneville Dam 800000 McNary Dam Priest Rapids Lower Granite Dam 700000 600000 lmonaS ko 500000 Chino Adult 400000 of er mbuN300000 200000 100000 0 1977 1982 1987 1992 1997 2002 Year FIGURE 4-1 Counts of adult Chinook salmon at Bonneville, McNary, Priest Rapids, and Lower Granite dams on the Columbia River (1977 to 2002)
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From page 78... ...
. It bears noting that the 2001 to 2003 returns of fall Chinook salmon, like in-river runs since the mid-1990s, also benefited from increased restrictions on ocean fishing.
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From page 79... ...
. Redd counts from Idaho's Salmon River basin provide addi tional information regarding temporal trends of spring/summer Chinook salmon listed by the Endangered Species Act.2 Redd counts in 1957, the first year of systematic surveys, were inflated by completion of The Dalles Dam in the lower Columbia River (Figure 4-4)
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From page 80... ...
. The harvest rate in the Columbia River between the river mouth and the upper limit of commercial fishing near the site of McNary Dam ranged from 40 to 85 percent before the 1960s, declined until 1974, and thereaf ter averaged less than 10 percent (Chapman et al., 1995)
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From page 81... ...
. FIGURE 4-6 Commercial landings of salmon and steelhead from the Columbia River in numbers of fish, 1938 to 2000.
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From page 82... ...
The majority of spring Chinook salmon, summer Chinook salmon, and steelhead counts in recent years showed that most of these fish originated from hatcheries. Only about one-fourth or less of spring/summer Chinook salmon and steel head that returned to the Snake and upper Columbia rivers in the past two decades have been of wild origin; thus, about 75 percent of the spring/summer adult Chinook salmon that return to the Snake River are produced in hatcheries.
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From page 83... ...
The Water Budget has subsequently evolved into a more exten sive and complex water management strategy intended to in crease instream water velocities, reduce travel times, and in crease survival rates of smolts as they migrate seaward through the impounded Columbia and Snake rivers (spring migrants smolt during the spring months, and summer-migrating ocean type Chinook migrate primarily in July and August)
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From page 84... ...
and a complex of storage reservoirs in Canada and Montana. In the Snake River basin, Dworshak reservoir, Brownlee reservoir, and the Hells Canyon complex -- all in Idaho -- augment flows (Figure 4-7)
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From page 85... ...
. The migration speed of salmon smolts dictates their expo sure time to hazards in reservoirs.
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From page 86... ...
and Bentley and Raymond (1976) estimated that after dam emplacement, travel times of yearling Chinook salmon and steelhead increased at least twofold over preimpoundment conditions.
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From page 87... ...
In the early 1990s, studies concluded that variability in smolt travel times was best explained as a function of a com bination of flows, water temperatures, and release dates (the lat ter of which is a surrogate for the level of smolt physiological development; Berggren and Filardo, 1993)
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From page 88... ...
Even now, with widespread use of PIT tags, opportunities to provide robust smolt survival estimates through the middle reach of the Columbia River are limited because of the small number of PIT detection systems there. Contemporary Investigations Translating river flows, or smolt migration rates, into smolt survival rates is the critical issue underpinning the rationale for providing flow augmentation and quantifying any associated benefits.
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From page 89... ...
Using a mixture of PIT-tagged yearling Chinook salmon and steelhead smolts from the Snake Basin, they found that travel time from Lower Granite Dam to McNary Dam was strongly correlated with flow volume, with the physio logical development of the smolts a contributing factor, particu larly for Chinook salmon. However, they could not identify a substantive or consistent relationship between smolt travel time and smolt survival through that same river segment.
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From page 90... ...
Northwest Power Planning Council (FPC, 2002) , stating that for juvenile steelhead and Chinook salmon spring migrants · a water travel time and survival relationship exists for spring migrating Chinook salmon and steelhead of Snake River and mid-Columbia River origin;
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From page 91... ...
Thus, predictor variables were typically correlated among themselves. In the middle reach of the Co lumbia River, the size of subyearling Chinook salmon was found to be the best predictor of migration speed between Rock Island and McNary dams (Giorgi et al., 1997)
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From page 92... ...
. Support for this recent conclusion was based largely on datasets acquired in the lower Snake River from the Lower Granite Project to McNary Dam on the Columbia River.
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From page 93... ...
The emphasis in this model is also on the Snake River. In formulating the summer model, weekly survival estimates for ocean-type subyearling Chinook migrating from release sites upstream to the tailrace of Lower Granite Dam, as estimated by the Fish Passage Center for the years 1999 and 2000, were employed.
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From page 94... ...
Extended migration travel times may cause delayed effects that could impair survival of smolts in the Columbia River estuary and after seawater entry. This hypothesis asserts that preimpoundment timing of seawater entry was synchronized with a "biological window." Extended migration travel times as sociated with impoundments and reduced velocities have dis rupted the natural timing of ocean entry, potentially placing smolts at a disadvantage.
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From page 95... ...
(2002) , for example, studied changes in the condition of year ling Chinook salmon migrating from Lower Granite Dam to Bonneville Dam (1998 to 2002)
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From page 96... ...
Fall Chinook salmon, for example, re cently began spawning in a formerly unused site in a Snake River tributary, the Clearwater River, because water releases from Dworshak Dam3 warmed the Clearwater River during win ter, providing a suitable environment for spawning and incuba tion. Similarly, releases of relatively warm water from Colum bia River storage reservoirs (most importantly Grand Coulee and Chief Joseph)
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From page 97... ...
Within the Columbia and lower Snake rivers, summer water temperatures now reach levels that clearly impose risks to juve nile salmonids. During the summer, subyearling Chinook salmon rear and migrate downstream when river temperatures exceed 20°C (Giorgi and Schlecte, 1997)
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From page 98... ...
developed a model which suggests that a decrease in water temperature from 21.5°C to 17°C could reduce the number of prey consumed by a northern pikeminnow from seven to four per day. This suggests that water temperature regulation measures that reduced Snake River water tempera tures could indirectly and locally enhance survival prospects of juvenile fall Chinook.
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From page 99... ...
(1998) conducted a study that had implications for summer flow augmentation in the Snake River.
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From page 100... ...
Using several smolt passage mod els, the incremental change in smolt migration speed for yearling Chinook salmon, steelhead, and fall Chinook salmon that may have resulted from flow augmentation water was estimated. It was concluded that Snake River flow augmentation increased water velocity through Lower Granite Pool an average of 3 to 13 percent during the spring.
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From page 101... ...
The reduction in Snake River water temperature associated with cold water releases from Dworshak Reservoir was greatest at Lower Granite Dam and diminished as water moved downstream to Ice Harbor Dam. Depending on the year and base flow characteristics, the change in temperature at Lower Granite Dam typically ranged from 1° to 4°F.
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From page 102... ...
: Underscoring these substantial uncertainties in flow augmentation rationale is the fact that summer draw downs in upstream storage reservoirs, for example Hun gry Horse Reservoir in Montana, to accomplish summer smolt flushing in the lower Columbia River has direct and potentially negative implications for nutrient mass bal ance and food web productivity in Flathead Lake, lo cated downstream from Hungry Horse. The issue involves balancing expected benefits to anadro mous fish with ecosystem functions and potential risks to other species.
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From page 103... ...
1) shading the stream and maintaining low water temperatures, (2)
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From page 104... ...
Chinook salmon in 2002 and 2003. This increase has generally been attributed to favor able ocean conditions.
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From page 105... ...
Within the body of scientific literature reviewed as part of this study, the relative importance of various environmental variables on smolt sur vival is not clearly established. When river flows become critically low or water temperatures excessively high, how
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From page 106... ...
The following chapter reviews efforts at cooperation across the Columbia River basin and identifies some of the limits of and lessons from these efforts and what they bode for future cooperative regimes across the basin.
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