EFFECTS OF POOL FLUCTUATIONS ON NATURAL RESOURCES IN THE ROCKY REACH PROJECT AREA

Prepared by:

A. E. Giorgi BioAnalysts, Inc. 7981 168th Avenue NE Redmond, WA 9805

and

M. D. Miller BioAnalysts, Inc. 3653Rickenbacker Ste 200 Boise, ID 83705

Prepared for:

Chelan County Public Utility District P.O. Box 1231 327 North Wenatchee Ave. Wenatchee, WA 98807

November 2000 2

TABLE OF CONTENTS

INTRODUCTION...... 3 FACTORS AFFECTING POOL ELEVATION...... 3 EFFECTS ON FISHERIES RESOURCES...... 4 Stranding ...... 4 Spawning...... 6 Wells Tailrace ...... 6 Chelan Falls...... 7 Fish Migration...... 7 RIPARIAN HABITAT ...... 9 REFERENCES...... 13

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INTRODUCTION

According to the directives provided in the Chelan PUD work statement, the purpose of this section is to investigate the potential effects of Rocky Reach Pool fluctuations on fisheries resources. The scope will include an assessment of effects on ESA-listed anadromous fish populations, as well as the riparian habitat bordering the pool.

The operation of Rocky Reach , and the Wells Project (Douglas County PUD), causes fluctuations in both surface water elevation and water velocity in Rock Reach Pool. Both of these responses may have an effect on salmonid stocks and their habitat. Potentially, reservoir dynamics can affect migration, spawning, rearing, and stranding of fish within the reservoir, as well as riparian zone structure and reservoir habitat. These issues are addressed herein.

FACTORS AFFECTING POOL ELEVATION

Changes in water level at the Rock Reach project can result from either drafting water at the dam or from fluctuating inflow to the reservoir, particularly as associated with Wells Project discharge. The forebay elevation is sensitive to drafting, but not Wells inflow. However, changes in discharge from does affect the water level in the upper reservoir. For example, between 25,000 cfs and 200,000 cfs a 25,000 cfs change in discharge can move the water elevation from 1.0 to 1.7 ft in the Wells tailrace (Chelan PUD 1991). As a consequence, discharge between 30,000-220,000 cfs can dramatically change pool elevation at Wells Dam tailrace (Figure 1).

Forebay operating levels at the Rocky Reach Project generally fluctuate over a narrow range of about two feet. In the 1991 Pool Raise Application, Chelan PUD noted that since 1972, the Rocky Reach forebay level was stable within the top two feet (elevation 705 - 707 feet) for 98% of the hours, and within the upper one foot 90% of the time

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(Chelan PUD 1991). Furthermore, forebay level changes slowly, because the surface area of the forebay is large in comparison to the hydraulic capacity of the powerhouse.

Changes in surface water elevation are more pronounced at the upstream portion of the reservoir (near Wells Dam tailrace) than near . The backwater profile developed by Stone and Webster Engineering can best depict this (Figure 1). With Rocky Reach forebay elevation 707’, as flow increases from 30,000 cfs to 220,000 cfs the surface water elevation at Azwell in the Wells tailrace increase from 707.5’ to 719’. At river mile 497, approximately half way down the reservoir the fluctuation is only 707’ to 708.5 over the same change in flow.

The frequency with which pool elevation changes are dictated by the frequency flow fluctuates. Daily load-following is the typical operating mode for the Wells and Rocky Reach projects. Changes in flow can be pronounced over a 24-h period. As an example we refer to Figure 2 (taken from Chapman et al. 1994). During the month of July over several years, daily fluctuations often exceeded 100,000 cfs. Lows typically were near 50,000 cfs at night and could exceed 150,000 cfs during the day.

Clearly, water velocity throughout the reservoir is sensitive to flow. Figure 3 illustrates this point. The index reach in this example includes the reach spanning Wells tailrace to . Chapman et al (1994) estimated water velocity through this reach over a range of flow, using the water volume displacement method. At 80,000-cfs water velocity through this index reach averages near 1 fps, whereas at 180,000 cfs velocity is estimated near 2.5 fps.

EFFECTS ON FISHERIES RESOURCES

Stranding

Changing water surface elevation can strand fish as water recedes. Smaller fish are particularly susceptible to this. Since smolt stages of ESA-listed salmonid stocks inhabit

Rocky Reach Project No. 2145 BioAnalysts, Inc. DRAFT REPORT 5 this reservoir, the potential for stranding is a concern. However the fish that are most susceptible to stranding are the summer/fall chinook salmon fry that are not listed under the ESA. They typically inhabit shallow-water, near-shore areas and embayments. Chinook fry move into shallows at night and have been observed to select depths less than 60 cm in areas with sand substrate (Hillman et al. 1988). As water levels recede, depressions form pools where oxygen can be depleted, or fish desiccate if water percolates through the substrate. However, the upper part of the reservoir where elevation fluctuations are most pronounced, has little shallow-water habitat where fry would be expected to congregate.

Large changes in inflow within short time periods result in water level fluctuations in the middle and upper reservoir that could strand fish. Changes in flow associated with load- following occur daily throughout the system (Figure 2). However, according to information compiled for the pool raise application in 1991, only one incident of fish stranding and mortality had been observed. That occurred in May 1988, as a result of an unusual combination of events an extreme reduction of flow in combination with near maximum drawdown of the Rocky Reach reservoir. These conditions were a consequence of flow reductions for bank stability tests at the , and drafting of the Rocky Reach forebay to maintain spill scheduled for bypassing downstream-migrant salmon and steelhead smolts. The fish kill was exacerbated because this event occurred in May, when recently emerged fall chinook fry were rearing throughout the shallow, low-velocity areas of the Rocky Reach Reservoir. No mortality estimates were reported in the report accounting of the incident.

To the best of our knowledge there have been no observed fish strandings in Rocky Reach pool since that date. We could not locate any reports describing stranding/mortality events. We also queried Chelan PUD biologists. They were not aware of any further incidents.

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Spawning

Changes in pool elevation can potentially affect spawning activity of salmonids in Rocky Reach Pool. Only summer/fall chinook have been documented as spawning in areas under the influence of Rocky Reach project operations. In 1990 and 1991, Giorgi (1992) investigated the effects of changes in Rocky Reach pool elevation on summer/fall chinook spawning in the reservoir and adjacent waters affected by pool operations. Spawning activity was observed in two areas. One site was downstream from the tailrace at Wells Dam, near river-miles 514-516. The second site was at the mouth of the near where it enters the Columbia River. The mouth of the Entiat River was included in those surveys in 1990 and 1991, but no redds we observed in the area influenced by the pool. However, four fall chinook redds were observed in the braided stream area well upstream from the boundary defining the pool (Giorgi 1992).

Wells Tailrace

Over the range of river discharge levels and associated surface water elevations that occurred in the fall of 1990 and 1991, water velocity across the spawning beds was swift. Velocity in the vicinity of redds typically exceeded 2-3 fps (Giorgi 1992). These velocities are well above the minimum (1.0 fps) observed at summer/fall chinook spawning areas in the Columbia River and some of its tributaries (Giorgi 1992). As synthesized by Giorgi (1992), the close proximity of the spawning areas to the Wells Dam ensures the maintenance of fast currents in this river-like segment of the reservoir. Normal operations of Rocky Reach Project maintain water velocities well above the minimum of 1.0 fps.

Potentially fluctuations in surface water elevation could affect redd distribution. If summer/fall chinook preferred shallow areas, there may be a risk of redd dewatering and desiccation or freezing, due to load-following. However, this does not appear to be an important concern at the Wells Dam spawning site, since redd deposition is deep, ranging from 5 to 32 feet deep, with the majority deposited at 18 to 24 feet deep (Giorgi 1992).

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Chelan Falls

Two factors affect water velocity and surface water elevation at Chelan Falls: (1) the discharge from the Chelan River and (2) the backwater effects from Rocky Reach Reservoir. During the fall when chinook salmon are spawning in this area, discharge from the Chelan River is usually relatively stable, near 2,000 cfs. Typically all the water passes through the powerhouse upstream from the spawning area, during the fall spawning period. Based on two years of observations, over the normal Rocky Reach forebay elevations, water velocity in the vicinity of the redds ranged from about 1.0 to 2.3 fps and typically exceeded 1.5 fps. The velocities equal or exceed the 1.0-fps minimum observed at other fall chinook spawning sites in the Columbia System (Giorgi 1992). We conclude that continued normal operations of the Chelan Falls powerhouse and Rocky Reach Project would maintain water velocities that are conducive to spawning in the Chelan River.

Adult salmon select the higher velocity areas for redd site construction in this area. As a consequence, redd deposition is pronounced in the deeper portions of the channel where flow is concentrated. These waters are deep and redds are distributed from 4-18 feet in these zones. Redds in these areas of dense deposition are not at risk of exposure to air across the current operating conditions associated with Chelan Falls powerhouse and Rocky Reach Project.

Fish Migration

Our review of the literature revealed no evidence to suggest that changes in surface elevation or water velocity associated with fluctuations in river discharge impair the migratory behavior of adult salmonids or lamprey passing through Rocky Reach Reservoir or other reservoirs in the mid-Columbia system.

The coordinated operation of the Columbia River hydroelectric system affects pool elevations in Rocky Reach Reservoir as well as current velocity through the reservoir. There is evidence for some populations of salmonids in the Columbia Basin that the

Rocky Reach Project No. 2145 BioAnalysts, Inc. DRAFT REPORT 8 migration rate of smolts is positively related to water velocity through impoundments (Berggren and Filardo 1993; Giorgi et al. 1997). Slower migration exposes smolts to predatory fish for longer periods, potentially increasing smolt mortality (Berggren and Filardo 1993). Additionally it has been hypothesized that slower migration may impair seawater adaptation if migration delay is too long.

Berggren and Filardo (1993) described a relationship between smolt migration rate and water velocity (as indexed by flow) for spring-migrating yearling chinook salmon and steelhead. They found that smolt travel time estimates for yearling chinook and steelhead in the Snake River and steelhead in the mid-Columbia River were inversely related to flow. That is, as flows increased smolt migration rate increased. However, in the case of the mid-Columbia steelhead, the predicted change in travel time per unit flow was small. Based on their bivariate model, as flows increased from 120 to 160 kcfs, travel time from the to McNary Dam decreased by only two days from 16.2 to 14.3 days, respectively.

Giorgi et al. (1997) investigated the relationship between smolt migration rate through the Mid-Columbia River and a suite of variables. Using PIT tag data for the years 1989- 1995, they found that the migration rate of yearling and subyearling chinook was not correlated with prevailing flow levels through the reservoirs. However, significant migration rate – flow relationships were evident for spring-migrating sockeye salmon and steelhead. Although the relationships were statistically significant, the values of the coefficients of determination were small, ranging from 0.31 to 0.46. This indicates a weak association between prevailing water velocity and smolt migration rate. According to Prairie (1996), when regression models yield coefficients of determination less than 0.65, they have poor predictive power or utility.

Water velocity through Rocky Reach Pool is not dictated by the operations of that single project. River discharge intensity and frequency are a result of the coordinated operation of the entire Columbia River hydroelectric system, from downstream. That system operates in response to power demand cycles, flood control, and flow

Rocky Reach Project No. 2145 BioAnalysts, Inc. DRAFT REPORT 9 management strategies directed at improving fish migration conditions. As such there is little flexibility on the part of the Rocky Reach Project to individually tailor operations with the specific intent of substantively altering velocity patterns in the reservoir.

Recently the National Marine Fisheries Service released the draft Biological Opinion for year 2000. That document prescribes flow targets that provide adequate migratory conditions suitable for salmonids migrating through the Columbia and Snake River systems. For the Mid-Columbia reach the target specified is 135 kcfs, as measured at from 10 April through 30 June. During the summer migratory period there is a target specified for the Columbia River at McNary Dam of 200 kcfs. No specific contribution from the Mid-Columbia system is specified for the summer period. Water management actions necessary to achieve the flow targets are implemented at the system level, by drafting storage reservoirs. The operation of individual run-of-river projects has negligible effects on flow targets. In fact, in the Biological Opinion, the NMFS does not specify any project specific operations directed at improving migration conditions through reservoirs. We think that position is sound and see no reason to be concerned that normal operations of the Rocky Reach Project will impair salmonids migration through the reservoir.

RIPARIAN HABITAT

Riparian zones play an important role in terrestrial and aquatic environments. They are found adjacent to streams, rivers, springs, ponds, lakes and reservoirs. Riparian areas provide many benefits, including stream bank stability, resistance to flow, bar sedimentation, large woody debris, and flood plain deposition (Hickin 1984, In: Malanson 1993). Wildlife benefit from riparian areas because they supply food, cover, and water. They also serve as migration routes and forest connections among habitats. Riparian areas also provide important nest and perch sites for waterfowl and raptors. Riparian areas support disproportionately more wildlife than most other North American habitats (Thomas et al. 1979; Stocek 1994, In: Morgan and Lashmar 1993). In arid and

Rocky Reach Project No. 2145 BioAnalysts, Inc. DRAFT REPORT 10 semi-arid regions, like Eastern , riparian habitats provide a unique reservoir of plant and animal diversity.

The construction and operation of in the mid-Columbia have altered riparian habitats. Construction of Rocky Reach Reservoir inundated riparian habitats in the natural floodplains of the mainstem Columbia River and tributaries such as the Entiat River. However, before hydroelectric development, large periodic floods that scoured stream banks and steep topography limited riparian habitat. Creation of Rocky Reach Reservoir reestablished the riparian zone on lands surrounding the present reservoir pool elevation. We expect that the ratio of floodplain to river channel area has decreased since creation of the reservoir. That decrease in flood plain area combined with topographically controlled flows limit riparian zone development and lateral flows necessary for seed dispersal, seed bed formation, and soil moisture. For much of Rocky Reach Reservoir the establishment and growth of riparian zones is probably a function of time, shoreline substrate, water level fluctuation and land development, particularly the uncultivated margins of irrigated orchards.

Shoreline habitat in the Rocky Reach Reservoir study area was inventoried in the mid- 1970’s and again in the early 1990’s (Payne et al. 1976; Ebasco 1991). In 1975, only 25 percent of the shoreline was riparian habitat, compared to 40 percent estimated in 1991. Riparian classification and inclusion of islands might account for minor differences in estimates of riparian shoreline. However, riparian habitat establishment and growth in the interim years would account for the increase in percent riparian shoreline. We expect that riparian areas have grown and become more established in the last ten years since the surveys conducted in 1991. Payne et al. (1976) noted that the oldest impoundment, Rock Island Reservoir, had the best-developed riparian shoreline. There, they estimated that 60% of the shoreline was occupied by riparian habitat. The establishment of riparian habitat may be related to the age of the reservoir. Rocky Reach Dam was built in 1961 (39 years ago) and Rock Island Dam was constructed in 1933 (67 years ago). More time may be required to establish and grow riparian habitat such as large mature cottonwoods.

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Riparian habitat along Rock Reach Reservoir is limited to about 100 ft from the shoreline (Chelan PUD 1991). Shoreline habitat along Rocky Reach Reservoir includes 341 acres of riparian habitat. That habitat was classified as deciduous trees/forested wetlands, riparian mixed, shrub/shrub wetlands, and grassland. Riparian habitats are primarily vegetated with black cottonwood, water birch, willow, red-osier dogwood, and cattails (Chelan PUD 1991). Other plant species observed in Rock Reach Reservoir study area are listed in Table 2. Deciduous riparian areas exhibit a diverse, well-developed multi- level overstory. The average tree cover was 68% but ranged from 15 to 100 percent. Average canopy height was relatively low at 36 ft. Ebasco (1991) estimated that riparian habitat was only 9 percent of the total terrestrial habitat acreage, which makes it the least abundant community type in Rocky Reach Reservoir (Table 1).

Seasonal as well as daily pool fluctuations determine the establishment of riparian plants. Several researchers (reported in Malanson 1993) discussed the importance of lateral flow to increase soil moisture, seedbed formation, and seed dispersal. The duration and frequency of flooding was also a primary factor influencing the internal structure of riparian forests (Malanson 1993). In Rocky Reach Reservoir, shoreline conditions downstream of Wells Dam are the result of water level fluctuation, erosion, and stream bank stabilization. The shoreline immediately downstream of Wells Dam is exposed rock, gravel shore, rip-rap, and bare ground (Ebasco 1991). With the exception of rip- rap, these conditions resemble historic photos taken before hydroelectric development. At the other extreme, near constant pool elevation at Rocky Reach forebay reduce lateral flows that provide moisture, sediments, and dispersal of seeds to shoreline habitats. However, these stable conditions reduce erosion from flooding and maintain water table levels that benefit riparian habitat.

Developed or disturbed areas occupied nearly 40 percent of the total area surveyed in 1991 (Ebasco 1991) (Table 1). These areas limit riparian development particularly when the areas are rip-rap, roads, and railroads. There, shoreline substrate would have limited soils for plants to become established. Other areas along the reservoir such as orchards, residential, industrial, and pasture offer little potential for development of riparian areas

Rocky Reach Project No. 2145 BioAnalysts, Inc. DRAFT REPORT 12 because of land management. Parks offer the best opportunity to increase riparian habitat and still provide recreational values.

Ebasco (1991) reported that development of riparian vegetation is limited by arid conditions, steep banks that are often stabilized by rip-rap, and residential and agricultural development along the shoreline. The riparian habitat along Rocky Reach Reservoir is also affected by hydroelectric operations. As mentioned earlier, pool elevation changes and subsequent velocity are more pronounced at Wells Dam tailrace than at the forebay of Rocky Reach Dam. Frequent and sometimes large changes in pool elevation combined with increased water velocity erode streambanks and prevent riparian establishment. Fluctuating flows from power peaking at Wells Dam affect shoreline conditions just downstream of the dam but do not appear to change pool elevation in the forebay of Rocky Reach Dam (Figure 1). The former, not the latter, limits establishment of a riparian zone in those areas. Shorelines with high gradients (steep banks) will have narrow floodplains. This is particularly true in areas if pool elevation is constant.

Flood control regulates pool elevation in Rocky Reach Reservoir to protect valuable shoreline areas. Increasing pool elevation to encourage lateral flow would be impractical and achieve limited benefit for increasing floodplain deposition and seed dispersal. The majority of riparian habitat along Rocky Reach Reservoir does not appear to be affected by hydroelectric operations. The lack of riparian habitat just downstream from Wells Dam is limited to the upper reservoir. We expect that since the surveys conducted in 1991 riparian areas have continued to grow and become established.

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REFERENCES

Berggren, T., and M. Filardo. 1993. An analysis of variables influencing the migration of juvenile salmonids in the Columbia River Basin. North American Journal of Fisheries Management 13:48-63.

Chelan County PUD No. 1. 1991. Rocky Reach Hydroelectric Project No. 2145 – application for raising the pool elevation from 707’ to 710’.

Chapman, D., A. Giorgi, T. Hillman, D. Deppert, M. Erho, S. Hays, C. Peven, B. Suzumoto, and R. Klinge. 1994. Status of summer/fall chinook salmon in the mid- Columbia Region. 411 pages, plus appendices.

Ebasco Environmental. 1991. Wildlife Habitat Evaluation for Rocky Reach Pool Raise Study-Final Report

Giorgi, A. 1992. Fall chinook salmon spawning in Rocky Reach Pool: effects of a three foot increase in pool elevation. Research report submitted to Chelan County PUD, 35 pages, plus appendices.

Giorgi, A., T. Hillman, J. Stevenson, S. Hays, and C. Peven. 1997. Factors that influence the downstream migration rates of juvenile salmon and steelhead through the hydroelectric system in the Mid-Columbia River system. North American Journal of Fisheries Management 17:268-282.

Hillman, T., D. Chapman, J. Griffith. 1988. Seasonal habitat utilization and behavioral interaction of juvenile chinook salmon and steelhead trout in the Wenatchee River, Washington. II. Nighttime habitat selection. Final report to Chelan County PUD, Wenatchee Washington.

Malanson, G. P. 1993. Riparian Landscapes. Cambridge University Press.

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Morgan, K. H., and M. A. Lashmar, Editors. 1993. Riparian habitat management and research, Proceedings of a workshop sponsored by Environment Canada and the British Columbia Forestry Continuing Studies Network, held in Kamloops, B.C., 4-5 May, 1993. Canadian Wildlife Service, Environment Canada, and Fraser River Action Plan.

Payne, N. F., G. P. Munger, J. W. Mattews, and R. D. Taber. 1976. Inventory of riparian habitats and associated wildlife along the Columbia and Snake Rivers, Vol. 4A: mid- Columbia River. U. S. Army Corps of Engineers, North Pacific Division.

Prairie, Y.T. 1996. Evaluating the predictive power of regression models. Canadian Journal of Fisheries and Aquatic Sciences 53:490-492.

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Table 1. Acreage of cover types in the Rocky Reach study area. Open water habitats not included (From Ebasco 1991).

Cummunitty Type Frequency Acreage Percent of Total Upland Conifer/Shrub 16 49.42 1.06 Upland Deciduous 3 2.72 0.06 Shrub Steppe 157 1024.46 21.89 Exposed Rock/Shrub Steppe 4 104.21 2.23 Grassland 42 139.95 2.99 Equisetum/Grassland 1 4.99 0.11 Forbland 16 69.6 1.49 Exposed Rock 109 34.12 0.73 Rock/Talus 6 0.85 0.02 Sand Bank 6 0.89 0.02 Sand Dune 17 11.33 0.24 Gravel Shore 55 57.3 1.22 Bare Ground 5 11.07 0.24 Subtotal 1510.91 32.29 Riparian Riparian Deciduous Trees/Forested Wetland 319 136.33 2.91 Riparian Mixed 4 0.88 0.02 Riparian Shrub/Shrub Wetland 363 114.76 2.45 Riparian Grassland 233 89.67 1.92 Subtotal 341.64 7.301 Wetland Aquatic Bed 979 20.92 Emergent Wetland 90 13.12 0.28 Subtotal 992.12 21.20 Disturbed/Developed/Modified Disturbed 17 80.99 1.73 Orchard 103 951.38 20.33 Pasture 12 90.59 1.94 Recreational 5 153.28 3.28 Residential/Industrial 105 350.24 7.48 Rip-Rap 160 137.58 2.94 Future Park 4 2 46.29 0.99 Railroad 5 2.31 0.05 Road 9 21.9 0.47 Subtotal 1834.56 39.21 All Community Types Total 4679.23 100.00

1 Percent riparian habitat increases to 9.27 percent if you remove wetland acreage from the total.

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Table 2. List of plants in the study area (from Ebasco 1991).

Common Name Scientific Name

Big sagebrush Artemesia tridentata Bitterbrush Purshia tridentata Rabbitbrush Chrysothamus spp. Ponderosa pine Pinus ponderosa Rocky Mountain juniper Juniperus scopulorum Black cottonwood Populus trichocarpa Willow Salix spp. White alder Alnus rhombifiola Black Hawthorne Crategus douglasii Himalayan blackberry Rubus discolor Red-osier Dogwood Cornus stolonifera Poison Ivy Rhus radicans Reed Canary-grass Phalaris arundinacea Tumble knapweed Centaurea diffusa Eurasion Milfoil Myriophyllum spicatum Orchard Grass Dactylis glomerata Clover Trifolium spp. Douglas Fir Pseudosuga menziesii Snowberry Symphoricarpus spp. Serviceberry Amelanchier alnifolia Cheatgrass Bromus tectorum Bluebunch Wheatgrass Agropyron spicatum Siberian Elm Ulmus pumila Snow Buckwheat Eriogonum niveum Sand-dropseed Sporobolus cryptandrus Needle-and-thread grass Stipa comata Indian ricegrass Oryzopus hymenoides Wild Rye Elymus cinerus Russian Thistle Salsola kali Thistle Cirsium spp. Vetch Vicea spp. Aspargus Asparagus officinalis Horsetail Equisetum spp. Water Birch Betula occidentalis Black Locust Robinia pseudo-acacia Russian Olive Elaeagnus angustifolia Quaking Aspen Populus tremuloides Pearhip Rose Rosa woodsii Shiny-leaf Spirea Spirea betulifolia Chokecherry Prunus virginia Golden Rod Solidago canadensis Sedges Carex spp. Lombardy Poplar Populus nigra Waterweed Elodea sp. Pondweed Potamogeton spp.

Rocky Reach Project No. 2145 BioAnalysts, Inc. DRAFT REPORT Figure 1. Backwater profile for Rocky Reach Reservoir (from CPUD 1991). Figure 2. Hourly flows at Wells Dam for the first three weeks of July, 1986-1992. Data from Douglas County PUD. Figure 3. Mean water velocity, estimated with volume replacement method, in three mid- Columbia reaches and in the Snake River between Lower Granite and Ice Harbor dams.