SKAGIT RIVER. HYDROELECTRIC PROJECT FERC No. 553 ROSS lAKE LEVELS ANALYSIS VOLUME I Report SKX 1991 § #10 I City of Seattle City light Department JUNE 1991 SKAGIT RIVER HYDROELECTRIC PROJECT FERC No. 553 Ross Lake Levels Analysis Volume I Report • Prepared by Ebasco Environmental, with assistance from Synergic Resources Corporation Submitted to Seattle City Light June 1991 EXECUTIVE SUMMARY I. Introduction The City of Seattle, City Light Department (the City) is the owner and operator of the Skagit River Hydroelectric Project, Federal Energy Regulatory Commission (FERC) No. 553. The original license for the project, issued in 1927, expired in 1977. Since that time, the City has been conducting a number of studies, many of them related to downstream fisheries. More recently, and in response to inquiries by FERC and the intervenors (1 ). the City has hired consultants to evaluate project impacts in several areas. One area of intensive study has been an analysis of the impact of Ross Lake levels. Operation of Ross Lake has been characterized by annual drawdowns of about 100 feet. (2) The lake is generally at or near full pool during the mid to late summer months, and reaches its lowest level in early spring. The annual cycle of Ross Lake levels has impacts on, and is affected by, a number of other resources. These include: downstream anadromous fisheries electric power generation erosion (includes archaeological resources) flood protection recreation resident fisheries visual quality The relationships between Ross Lake levels and these resources are not only important, but most of them have not previously been quantified or otherwise studied in depth. The City has commissioned a series of studies to evaluate these relationships. These and other relevant studies are listed in the report bibliography, section 7.0. This report contains the resu Its of those studies. (1) U.S. Department of the Interior (National Park Service, Fish and Wildlife Service, Bureau of Indian Affairs), U.S. Department of Commerce (National Marine Fisheries Service), U.S. Department of Agriculture (Forest Service), Skagit System Cooperative Tribes (Upper Skagit, Sauk-Suiattle, Swinomish), Washington State Departments of Ecology, Fisheries, and Wildlife, and North Cascades Conservation Council. (2) Diablo and Gorge Lakes are operated as diurnal reservoirs for Ross Lake; although their levels go up and down, they do so on a much smaller scale than Ross Lake­ about five feet-and on a daily and not annual basis. 1 II. Current Impacts of Ross Lake Drawdowns on Visual Quality, Recreation, and Resident Fisheries The studies looked at the current impacts of the annual drawdown on visual quality. recreation, and resident fisheries. The major conclusions in these areas are as follows: A. Visual Quality The visual contrast (3) and single user impacts (3) of Ross Lake drawdowns vary from low to high and depend on the time of year and location of the view. The studies showed that viewers generally are not present during the maximum drawdown (February through April); the overall visual quality impact (3) of Ross Lake drawdowns is therefore low. The majority of viewers see Ross Lake when the lake level is at or near full pool-July through September-when the visual contrast and single user impacts are low. B. Recreation The primary non-aesthetic recreation impact of the annual Ross Lake drawdown is on boaters, due to diminished access to the lake via boat ramps and docks and to boat-in campground facilities. Boat ramp and campground access is most affected in May and June. However, the studies showed that the number of boaters in May and June is about one-fifth of the total number of annual users, so the impact is low. (Boaters are not generally presentwhen the lake is very low in April and alter October.) The annual drawdown has a beneficial impact on downstream recreation by modulating the natural short-term extremes of Skagit River flows. The operating regime of the Skagit Project allows for a longer whitewater boating season on the upper Skagit by providing sufficient late-summer flows. This results in peak use during August and September, which is not typical for whitewater opportunities, and probably leads to higher total use than would occur with unregulated flows. Scenic floating and boat fishing are made easier by maintaining relatively more stable flows that provide ample water for boating. While not specifically a product of the annual drawdown, the flood control provided by Ross dam helps to reduce Skagit River flood peaks, making river-oriented recreation activities easier and safer and reducing damage to shoreline recreation facilities. C. Resident Fisheries The annual Ross Lake drawdown has mixed effects on resident fisheries in the following ways: 1) the drawdown increases potentially available spawning habitat in tributary streams as the Jake recedes from approximately elevation 1595 feet, although the amount of habitat at these lower elevations is less than that available at full pool; 2) as the lake level rises in late spring, fish redds in tributary streams are inundated by rising lake levels, which in some cases kills the unhatched eggs; 3) the spawning habitat above full pool (3) These terms are defined and explained in detail in Ross Lake Early-Season Recreational Activity and Visual Quality Assessment (Parametrix, 1989). In that study the word index is often used in place of impact. 2 elevation in some tributaries is not accessible until the lake is almost at full pool, and this generally occurs too late in the spring for the fish to use the habitat for reproduction; and 4) the drawdown permits the avoidance of spill over Ross dam which is harmful to the fishery. The studies conclude that current Ross Lake drawdowns probably do not have significant overall impacts on the already enhanced resident fishery. Ill. Potential Impacts of Early Refill Alternatives on Recreation, Downstream Anadromous Fisheries, Resident Fisheries, Power Production, Flood Protection, and Shoreline Erosion As part of the lake level studies, the consultants investigated the potential impacts of a series of early refill alternatives on other resources. The identified impacts would be on reservoir and downstream recreation, downstream anadromous fisheries, power production, and flood protection. A. Recreation The studied early refill alternatives would improve the recreation experience on Ross Lake in two ways: 1) the aesthetic experience would improve; and 2) access to the lake and to boat-in campgrounds would be less affected by reservoir drawdown. Both of these benefits would occur primarily in May and June. The improved recreation opportunities might result in an increase in early season use of Ross Lake; the studies calculate that a realistic projection of increased on-lake use would be less than 3 percent over current levels, or about 1000 user days (4). This projection is based on an aggressive refill target of full pool on May 31; other alternatives would have a correspondingly lower increase. The study estimated the dollar value of the realistic increase in recreational use due to May 31 refill as less than $20,000 per year; the maximum conceivable benefit would be $243,500 per year with this alternative. Early refill would affect downstream recreation activities by reducing Skagit River flows from January through March or April, and increasing flows from May through July. The primary effect of this change would be on upper Skagit whitewater boating, where current May and June use might be displaced or reduced because flows would be too high at this time of year. Winter flows would still be sufficient for scenic floating and boat fishing, while opportunities for these activities would also probably not be diminished by the higher May­ July flows. B. Anadromous Fisheries In the time since the original Skagit project license expired in 1977, the City in cooperation with appropriate intervenors, and based on numerous, detailed studies, has implemented changes in the operation of the project to further project downstream anadromous fisheries. The City and the intervenors have continued to work toward an overall agreement for an operating regime for that license. (4). A user day, or activity day, is one visitor present for any part of one day. 3 The present studies were designed to indicate the impacts of various Ross Lake early season refill alternatives on the downstream anadromous fisheries due to changes in flows. The studies included sensitivity analyses to compare the impacts of a range of flows on protection levels of the anadromous fisheries. Early season refill ha the potential to affect downstream anadromous fisheries by 1) changing the timing of flow releases from the reservoirs, 2) affecting the project's abilities to meet minimum flow requirements at different times of the year, and 3) increasing spill. The impacts are summarized as follows: Early season refill causes definite, negative impacts on pink and chum salmon. Early season refill does not significantly impact chinook salmon. Early season refill causes modest increases in protection in certain months of the steelhead run, and little or no impact in other months. The overall impact on numbers of fish is negative because the steelhead runs which are benefitted are very small in comparison with the salmon runs which are harmed. The magnitude of the adverse impact increases substantially with earlier refill. • Increased minimum flows are a key element in protecting downstream anadromous fisheries. Early season refill impairs the project's ability to meet increased minimum flows. C. Resident Fisheries Early season refill could open up some currently unavailable spawning habitat to fisheries resident in Ross Lake. The positive effect of increased availability of spawning habitat is offset by a reduction of habitat due to flooding of other tributary streams which currently provide spawning below the full pool elevation. Providing new access to the spawning habitat in the tributary streams might also displace utilization by resident fisheries currently present in those streams.