Introduction
The Northwest Power Planning Council in its Fish and Wildlife Program (FWP) specifies a Council policy "The program preference is to support and rebuild native species in native habitats, where feasible." (NPPC, 1994, Section 2.2A). The Council, through its FWP, has expressed an interest in evaluation of the effects of improved flows on production of fall chinook in the Hanford Reach (NPPC, 1994, Section 6.1C.2).
The Independent Scientific Advisory Board (ISAB) initiated this report because of our special interest in the stock of fall chinook that spawns in the Hanford Reach. Our interest has its origins in the Independent Scientific Group of the Northwest Power Planning Council and Bonneville Power Administration (ISG) and is now shared by all members of the ISAB. That interest developed during preparation of Return to the River (ISG, 1996), in which we identified the Hanford Reach as the only remaining significant mainstem spawning area for fall chinook in the Columbia River (Geist, 1995; ISG, 1996; NRC, 1996; Huntington et al., 1996; Whidden, 1996). It contains the largest natural spawning population of chinook above Bonneville Dam (Dauble and Watson, 1997).
Over the last two decades, Hanford Reach fall chinook have continued to be productive, while other stocks have declined. Our continuing interest and concern for that particular stock of fish arises precisely because it is a relatively healthy stock. It deserves our attention as we attempt to identify and measure the factors that are responsible for its continuing productivity, so that these favorable elements might be extended to other stocks. Furthermore, we believe the productivity of the Hanford stock can be improved.
As our interest in this stock developed, we persuaded the Council, in the summer of 1995, and again in May, 1996, to visit the Hanford Reach. During their 1996 site visit, Council members observed numerous juvenile fall chinook that had become stranded on the bank as river flow had been suddenly reduced, exposing the near shore areas where these fish had concentrated. Following that visit, the ISG recommended that there be a study to identify the magnitude of the stranding and to suggest appropriate minimum flows or ramping rates that would provide protection for these fish.Such a study was funded by BPA in 1997. Further information from that study is provided below.
Fall Chinook in the Hanford Reach
There are several reasons for the continued productivity of fall chinook in the Hanford Reach: 1) suitable conditions for natural spawning are present in the form of required velocities of flow, and upwelling of water through gravel substrate[1]; 2) the hatchery at Priest Rapids contributes fish to the population[2]; 3) success of natural spawning is enhanced by regulation of river flows out of the upper and mid-Columbia River dams at the time of spawning and during incubation of the eggs; and 4) the Hanford Reach offers habitat for rearing of juvenile chinook once they have emerged from the spawning gravel and begun feeding.
Considering the ISG's conceptual foundation (ISG, 1996), a fifth factor is probably involved in the continuing productivity of these fish. That is the effect of ocean conditions on the survival of fall chinook from the Hanford Reach. Clearly, during the time that flow regulation has been undertaken, ocean conditions have not been unfavorable for the survival of this particular stock, although returns are somewhat variable. It must be recognized that at some time unfavorable conditions could temporarily act to obscure the benefits of flow regulation.
Fluctuations in flow affect the suitability and productivity of the freshwater habitat, as we explain below. Flow regulation for certain purposes is accomplished through procedures established in the Vernita Bar Agreement between the three mid-Columbia P.U.D.s (Grant, Chelan and Douglas County P.U.D.s), Bonneville Power Administration, the fishery agencies and three treaty Indian tribes. Regulation of river flows in the Hanford Reach maintains suitable habitat conditions for spawning during the fall, and for incubation of the eggs during winter and spring each year. Loss of suitable habitat has been a universal factor contributing to the decline of Columbia River salmon. Regional reviews of salmonid status strongly implicate habitat degradation as a major contributing cause of population decline (ISG, 1996; NRC, 1996; Huntington, et al., 1996; Mundy, 1996; Myers et al., 1998). Provision of suitable habitat is essential for long-term survival of chinook in the Hanford Reach as it is elsewhere.
Vernita Bar Agreement
Development of the hydropower system has made possible the storage of spring runoff for later power production. In addition, it has made possible daily and hourly fluctuations in flow to correspond with power demand (load following). Load following is most likely to occur during times of low runoff when the power operators are motivated to conserve water for use during periods of peak demand.
Rapid reductions in flow in the Hanford Reach in early spring in the 1970's were observed to lead to dewatering of chinook redds that had been deposited the previous fall (Bauersfield, 1978; Chapman et al., 1983). The Washington Department of Fisheries entered a petition with the Federal Energy Regulatory Commission in 1976 to establish minimum flows of 70 kcfs out of Priest Rapids Dam during spawning and incubation of fall chinook (Carlson and Dell, 1989). The State of Oregon, the National Marine Fisheries Service and later, certain treaty Indian Tribes joined in the petition. An agreement was reached to conduct studies over a four-year period (Chapman et al., 1983). The studies focused on chinook spawning at Vernita Bar located about 4 miles below Priest Rapids Dam. Vernita Bar is the first major spawning area below Priest Rapids Dam for the fall chinook associated with the Hanford Reach. About one-third of the redds observed in the Hanford Reach occur at Vernita Bar (Carlson and Dell, 1989). Another one-third occur at Locke Island (Dauble and Watson, 1997). Studies revealed that management of flows during the fall spawning period to maintain a maximum level of flow could limit the area within which spawning occurred at Vernita Bar. Once eggs were deposited in the redds, a minimum flow level was identified that was needed to maintain coverage of the redds until the fry emerge the following spring (Chapman et al., 1983).
In 1988 a Long Term Vernita Bar Settlement Agreement was reached. It extends over the period 1988 to 2005. The Agreement establishes procedures to be used in the determination of river flow out of Priest Rapids Dam that are associated with 1) the initiation of spawning, 2) a critical flow level which establishes a minimum flow needed for continued submergence of the redds, and 3) an emergence date which marks the end of the period identified for maintenance of coverage of the redds. The particular maximum flow level that occurs during spawning varies from year to year, depending upon the water supply in the basin. However, the Agreement calls for maintaining flows out of Priest Rapids Dam at or below 70 kcfs in the daytime (spawning time) to discourage spawning at higher elevations and for maintaining flows during incubation to minimize dewatering of redds (Carlson and Dell, 1989; 1991). During incubation, minimum flow is set at the highest flow that occurred during spawning. In 1998, that minimum flow was 65 kcfs.
In order to live up to the terms of the Agreement, Grant County P.U.D., which is operator of Priest Rapids Dam and Wanapum Dam, immediately upstream, requires the cooperation of Chelan County P.U.D., operator of Rock Island and Rocky Reach dams, Douglas County P.U.D., operator of Wells Dam, and the cooperation of Bonneville Power Administration (BPA), operator of dams further upstream. Cooperation of BPA is vital to the Agreement because the storage capacity of the P.U.D. dams is too small to provide the necessary water sources for the flows required under the Agreement. The basic water sources are Grand Coulee Dam and reservoirs further upstream. Consequently, all of the parties named are participants in the Vernita Bar Agreement.
There can be little doubt that the procedures included in the Agreement for maintaining flows designed to continue the functionality of the habitat have been a positive factor in the continued productivity of the Hanford Reach fall chinook.
THE PRESENT PROBLEM
Fluctuations in Flow after Emergence of Chinook Fry
Emergence of chinook fry from the gravels normally begins sometime in March and is completed in May each year (Carlson and Dell, 1989). While the Agreement provides for minimum flows that will avoid drying of the redds, it does not prevent raising flows above the level of the redds once spawning is completed, nor does it prevent sudden reductions in flow down to the level of the redds. As a consequence, fry that have emerged from the redds in March are subject to stranding as they move out into newly inundated areas created by high flows. Additionally, once emergence is completed, (normally after the middle of May) there is no longer a requirement to maintain flows at any level. In years with low runoff or low supply at that time of year, power operators attempt to conserve the supply by following the load, with consequent sharp reductions in flow at night and on weekends (Figures 1A and 1B). The figures illustrate hourly flow out of Priest Rapids Dam during the early portion of fry emergence, April 15 to May 5, 1998 and the late portion, May 15 to May 25. Although emergence normally will be completed during the late portion, fry will still be present for some time after emergence.
Figure 1A. Priest Rapids Dam Hourly Flow Fluctuations, April 25 to May 5 (click to enlarge)
Figure 1B. Priest Rapids Dam Hourly Flow Fluctuations, May 15-25 (click to enlarge)
Stranding of Juvenile Chinook
Parties to the Vernita Bar Agreement did not foresee the potential problem that would be created by rapid changes in flow once the fry emerged from the gravel. The reasoning no doubt was that the fish would have sufficient mobility to be able to move with the water. However, this has proved not to be the case.
In response to the ISG recommendation for a study of stranding of fall chinook in the Hanford Reach, a study was funded by BPA in 1997. Washington Department of Fish and Wildlife commenced the study in 1997, a year with high spring runoff, when the problem did not occur. At our June 16, 1998 meeting of the ISAB we received a report on the 1998 study findings from Paul Wagner of the Washington Department of Fish and Wildlife. In the spring of 1998, significant numbers of fall chinook juveniles were again found to be stranded above the riverbank at times when flows were suddenly reduced.
Other Adverse Effects of Load Following
Adverse effects of sudden changes in volume of river flow are well documented in the scientific literature. (See reviews in ISG, 1996 and ISAB, 1997.) Short-term fluctuations associated with power peaking operations produce a large zone along each side of the river where aquatic plants and animals can not live. Thus, the food source for juvenile salmon is reduced or eliminated. Subsiding flows, in effect, lead to abandonment of the most productive zone in the river, the shallow water zone (Stanford and Hauer, 1992). We previously called attention to this problem in our report ISAB 97-3, (titled "Ecological impacts of the flow provisions of the Biological Opinion for endangered Snake River salmon on resident fishes in the Hungry Horse and Libby systems in Montana, Idaho, and British Columbia") wherein we noted that the effects of river regulation on the ecosystem in the Kootenai River have been studied extensively. These studies revealed a reduction in diversity and productivity of the food web resulting from rapid, daily fluctuations in flow.
THE NORMATIVE RIVER
The concept of the normative river, described in Return to the River (ISG, 1996) suggests moving toward restoration of natural river features as a means of rebuilding salmon and steelhead populations. Certainly, the sharp fluctuations in flow that result from load following, at times on an hourly basis, must be viewed as one of the more unnatural features of the hydroelectric system in the Columbia Basin.
We note a number of examples where load following has been abandoned as a mode of operation for hydroelectric power plants. Without attempting to conduct a thorough search, we are aware of several examples. There is a FERC requirement for stable flows out of Kerr Dam at Flathead Lake, Montana. A Settlement Agreement between Washington Water Power Co. and the Spokane Tribe calls for maintenance of constant minimum stream flows below Little Falls Dam on the Spokane River. On the Nisqually River, the cities of Chehalis and Tacoma reached a Settlement Agreement with the Nisqually Tribe, in which they agreed to eliminate power peaking at their dams.
CONCLUSIONS
The productivity of fall chinook in the Hanford Reach can be increased by extending the time period during which fluctuations in flow out of Priest Rapids Dam are avoided. The duration of stable flows should be extended to include the time in the spring when the juvenile salmon are associated with near-shore areas prior to their movement downstream (typically from mid-March to late May). Steady increases in flow do not create a problem as long as they are not followed by decreases that can lead to stranding.
Stable flows can be expected to have benefits for other fishes in upstream areas of the mainstem that will be affected, as well as those spawning in the Hanford Reach. For example, smaller populations of chinook have been observed spawning in tailrace areas below each of the six mid-Columbia dams from Chief Joseph to Priest Rapids dams (Horner and Bjornn, 1979; Giorgi, 1992). Protection and enhancement of this most productive zone in the river, the shallow water zone, will likely have benefits to the juveniles of these and other salmon stocks upstream, providing improved resting and feeding habitat for them during their migration to the ocean. (See ISG, 1996 for a description of downstream migration, also Dauble et al., 1989, and Key et al., 1994; 1995).
We note that similar spawning of chinook has been observed in the tailraces of three Snake River dams, Lower Granite, Little Goose and Lower Monumental dams (Garcia et al., 1997; Dauble et al., 1995), and below Bonneville Dam (Hymer, 1997).
RECOMMENDATION
We strongly recommend that the Council and NMFS call for BPA and the mid-Columbia P.U.D.s to annually, beginning in 1999, augment the protection of spawning of fall chinook in the Hanford Reach by maintaining stable flows out of Priest Rapids Dam during the period of emergence of fry from the redds, and by continuing stable flows until the fry have moved downstream. There should be no load following or other sharp fluctuations in flow in that period until such time in the spring each year when it is determined by field observations that the danger of stranding of juvenile salmon has passed.
REFERENCES CITED
Bauersfield, K. 1978. The effect of daily flow fluctuations on spawning fall chinook in the Columbia River. Washington Department of Fisheries. Technical Report No. 38. 32pp
Carlson, C. and M. Dell 1989. Vernita Bar monitoring for 1988-1989. Annual Report. Grant County P.U.D. No.2, Ephrata, WA. 47 pp
Carlson, C. and M. Dell 1991. Vernita Bar monitoring for 1990-1991. Annual Report. Grant County P.U.D. No. 2, Ephrata, WA. 33 pp
Chapman, D.W., D.E. Weitkamp, T.L. Welsh, and T.H. Schadt 1983. Effects of minimum flow regimes on fall chinook spawning at Vernita Bar 1978-1982. Don Chapman Consultants, Inc. Report to Grant County P.U.D. No. 2, Ephrata, WA. 132 pp, plus appendices
Dauble, D.D., T.L. Page and J.R.W. Hanf 1989. Spatial distribution of juvenile salmonids in the Hanford Reach, Columbia River. Fishery Bulletin 87:775-790
Dauble, D.D., R.L. Johnson, R.P. Mueller, C.S. Abernathy, B.J. Evans, and D.R. Geist. 1994. Identification of fall chinook salmon spawning sites near Lower Snake River hydroelectric projects. Annual Report, 1993. Pacific Northwest Laboratory. Report to U.S. Army Corps of Engineers, Walla Walla, WA.
Dauble, D.D. and D.G. Watson 1997. Status of fall chinook salmon populations in the mid-Columbia River 1948-1992. North American Journal of Fisheries Management 17:283-300
Garcia, A.P., W.P. Conner, R.D. Nelle, R.D. Waitt, E.A. Rockhold, and R.S. Bowen. 1997. Fall chinook salmon spawning ground surveys in the Snake River, 1995. pp. 1-17 In D.W. Rondorf and K.T. Tiffan. Identification of the spawning,, rearing and migratory requirements of fall chinook salmon in the Columbia River Basin. U.S. Geological Survey, Columbia River Research Laboratory, Cook, WA. Annual Report to BPA. Project No. 91-029. Contract No. DE-A179-91BP21708
Geist, D.R. 1995. The Hanford Reach: What do we stand to lose? Illahee:11:130-141
Giorgi, A.E. 1992. Fall chinook spawning in the Rocky Reach pool. Effects of a three foot increase in pool elevation. Research report to Chelan County P.U. D. No. 1, Wenatchee, WA
Horner, N. and T.C. Bjornn. 1979. Status of upper Columbia River fall chinook salmon (excluding Snake River populations). U.S. Fish and Wildlife Service. Cooperative Fishery Research Unit. University of Idaho, Moscow, ID
Huntington, C., W. Nehlsen, and J. Bowers. A survey of healthy native stocks of anadromous salmonids in the Pacific Northwest and California. Fisheries:21(3):6-14
Hymer, J. 1997. Results of studies on chinook spawning in the mainstem Columbia River below Bonneville Dam. Washington Department of Fish and Wildlife. Columbia River Progress Report 97-9. Battleground, WA
ISAB (Independent Scientific Advisory Board) 1997. Ecological Impacts of the flow provisions of the Biological Opinion for endangered Snake River salmon on resident fishes in the Hungry Horse and Libby system in Montana, Idaho and British Columbia. Report to the Northwest Power Planning Council and National Marine Fisheries Service. Portland,. OR. ISAB 97-3. 31 pp
ISG (Independent Scientific Group of Northwest Power Planning Council) 1996. Return to the River. Report to the Northwest Power Planning Council ISG 96-6. 584 pp
Key, L.O., R. Garland and E.E. Kerfoot 1995. Nearshore habitat use by subyearling chinook salmon in the Columbia and Snake rivers. pp. 74-107 in D.W. Rondorf and K.F. Tiffan (eds.). Identification of the spawning, rearing and migratory requirements of fall chinook salmon in the Columbia River Basin. Annual Report, 1993. U.S. Geological Survey, Columbia River Research Laboratory, Cook, WA. Report to Bonneville Power Administration. Report No. DOE/BP-21708-3
Key, L.O., J.A. Jackson, C.R. Sprague and E.E. Kerfoot 1994. Nearshore habitat use by subyearling chinook salmon in the Columbia and Snake rivers. pp 120-150 in D.W. Rondorf and W.H. Miller. Identification of the spawning, rearing and migratory requirements of fall chinook salmon in the Columbia River Basin. Annual Report, 1992. U.S. Geological Survey, Columbia River Research Laboratory, Cook WA. Report to Bonneville Power Administration. Report No. DOE/BP-21708-3
NRC (National Research Council). 1996. Upstream: Salmon and Society in the Pacific Northwest. Report of the Committee on Protection and Management of Pacific Northwest Anadromous Salmonids for the National Research Council of the National Academy of Sciences. Washington D.C. National Academy Press. 389 pp.
Stanford, J.A. and F.R. Hauer. 1992. Mitigating the impacts of stream and lake regulation in the Flathead River catchment, Montana, U.S.A.: an ecosystem perspective. Aquatic Conservation: Marine and Freshwater Ecosystems 2:35-63. Wiley and Sons
Whidden, S.M. 1996. The Hanford Reach: Protecting the Columbia's last safe haven for salmon. J. Env. Law 26:265-297
[1] Specific requirements of flow and upwelling of water for successful natural spawning of chinook are described in ISG 96-6 (1996).
[2] Grant County Public Utility District Number 2, Ephrata, Washington, annually provides a report to the Federal Energy Regulatory Commission on the activities at Priest Rapids Hatchery.
