BENTHIC MACROINVERTEBRATE SURVEY 1999 First-Draft ROCKY REACH HYDROELECTRIC PROJECT FERC Project No. 2145 November 17, 2000 Prepared by: Duke Engineering & Services, Inc. Bellingham, Washington & RL&L Environmental Services Ltd. Edmonton, Alberta Prepared for: Public Utility District No. 1 of Chelan County Wenatchee, Washington Benthic Survey TABLE OF CONTENTS SECTION 1: INTRODUCTION................................................................................................... 1 1.1 Site Description ............................................................................................................................................. 1 1.2 Purpose of Study............................................................................................................................................ 1 1.3 Objectives...................................................................................................................................................... 2 SECTION 2: METHODS ............................................................................................................ 3 2.1 Benthic Macroinvertebrates........................................................................................................................... 3 2.2 Drift ............................................................................................................................................................... 7 2.3 Molluscs ........................................................................................................................................................ 7 SECTION 3: RESULTS AND DISCUSSION............................................................................ 11 3.1 Benthic Macroinvertebrates......................................................................................................................... 11 3.2 Drift ............................................................................................................................................................. 14 3.3 Molluscs ...................................................................................................................................................... 16 SECTION 4: SUMMARY AND CONCLUSIONS ...................................................................... 25 4.1 Benthic Macroinvertebrates......................................................................................................................... 25 4.2 Drift ............................................................................................................................................................. 25 4.3 Molluscs ...................................................................................................................................................... 25 SECTION 5: LITERATURE CITED .......................................................................................... 27 LIST OF TABLES Table 2-1: Biometrics used to construct the B-IBI score. ............................................................................................. 6 Table 3-1: Comparison of water quality parameters at selected locations. ................................................................. 11 Table 3-2: Habitat features of the Rocky Reach Project benthic sampling sites, 1999............................................... 12 Table 3-3: Mean (n=3) number of taxonomic groups, density, and the B-IBI biotic index among the Rocky Reach Project benthic sampling sites, 1999................................................................................................................... 14 Table 3-4: Dominant taxon, percent composition and drift density found in the Chelan and Entiat River during four sampling periods. ................................................................................................................................................ 15 Table 3-5: Chelan River zooplankton. ........................................................................................................................ 15 Draft Study Report Rocky Reach Project No. 2145 November 17, 2000 Page i SS/2539 Benthic Survey LIST OF FIGURES Figure 2-1: Benthic Macroinvertebrate and Mollusc Sampling Locations in the Rocky Reach Reservoir................... 9 Figure 3-1: Daily discharge of the Columbia River at the Rocky Reach Dam (U.S. Gelogogical Survey Station Code 12453700). .......................................................................................................................................................... 18 Figure 3-2: Percent total abundance attributable to different taxa of benthic macroinvertebrates collected from the Rocky Reach Project area, 1999. ........................................................................................................................ 21 APPENDICES APPENDIX A: BENTHIC MACROINVERTEBRATE DATA APPENDIX B: DRIFT DATA APPENDIX C: MOLLUSC DATA APPENDIX D: PHOTOGRAPHIC PLATES Rocky Reach Project No. 2145 Draft Study Report SS/2539 Page ii November 17, 2000 Benthic Survey SECTION 1: INTRODUCTION 1.1 Site Description Chelan County Public Utility District No. 1 (Chelan PUD) operates hydroelectric facilities at the Rocky Reach Dam upstream of the City of Wenatchee. Located at river mile 473.7 (distance upstream from the Pacific Ocean) on the Columbia River, the Rocky Reach hydroelectric project consists of 11 generating units that produce up to 1287 MW. The dam also has 12 gated spillway openings. The hydraulic capacity of the Rocky Reach powerhouse is 214,227 cfs (6067 m3/s). Operated as a run-of-river facility, Rocky Reach Dam has little pondage and no usable storage volume. A comprehensive description of the Rocky Reach hydroelectric project is provided in Chelan PUD (1991). The Rocky Reach hydroelectric project impounds 43 miles (69 km) of the Columbia River from Rocky Reach Dam to Douglas County PUD's Wells Dam [Federal Energy Regulatory Commission (FERC) No. 2149] at river mile 517. The reservoir created by the Rocky Reach Dam is known as Lake Entiat and has a surface area of 9108 acres (3686 hectares). The drainage area upstream of the Rocky Reach Dam is approximately 87,760 mi2 (227,300 km2). The annual median flow from Rocky Reach Dam between 1973 and 1998 was 105,790 cfs (3000 m3/s). Two large tributaries enter the Columbia River from the west: the Entiat River at river mile 483 and the Chelan River at river mile 503. The Lake Chelan Hydroelectric Project (FERC No. 673) is located on the Chelan River, and is owned and operated by Chelan PUD. The project consists of a diversion dam constructed at the natural outflow of Lake Chelan and a powerhouse near the river mouth downstream of the diversion dam. Chelan PUD (1999) provides a complete description and review of water resources in the vicinity of the Rocky Reach Reservoir. Chelan PUD is permitted to operate the Rocky Reach Hydroelectric Project according to terms and conditions contained in the FERC license (No. 2145) issued 12 July 1956. A license was amended 23 May 1968 for the addition of four generating units. The existing license expires 30 June 2006. Chelan PUD is seeking a new federal license to operate the Rocky Reach hydroelectric project. The FERC relicensing process includes extensive planning, environmental studies, agency consultations, and public involvement, requiring several years of preparation. The process requires FERC to give equal consideration to power generation, fish and wildlife enhancement, protection of recreational opportunities, and preservation of other aspects of environmental quality. 1.2 Purpose of Study Currently there is inadequate information regarding benthic macroinvertebrate species composition and abundance within the Rocky Reach Reservoir. In general, the benthic community of a reservoir is dominated by chironomids (midges) and oligochaetes (bristle worms) (Mullan 1986). However, clams and mussels, especially the introduced Asian species Corbicula fluminea are common in Rocky Reach Reservoir (Chelan PUD 1999). Macroinvertebrates will inhabit both lentic (standing water, e.g., lakes and ponds) and lotic (running water, e.g., rivers and springs) environments. The Project Area is composed of both these environments. Swift water velocities and larger substrates (gravels, cobbles, and boulders) Draft Study Report Rocky Reach Project No. 2145 November 17, 2000 Page 1 SS/2539 Benthic Survey dominate the upper reaches of the reservoir, while the lower reaches have minimal water velocities and substrates that consist of sand, silt, and aquatic macrophyte beds. Unique macroinvertebrate communities may occur in these distinct environments. Therefore, the main focus of this study is to describe the benthic fauna and the habitats in which they occur. Past research efforts have shown that benthic assemblages, quantified by “metrics” or “indices”, can provide an indicator of water quality within a stream or reservoir (e.g., EPA 1998, Plafkin et al. 1989). Lake benthic metrics are responsive to stresses, similar to stream invertebrate metrics, with some adjustments given the changes in environments. Evaluation of the changes in the metrics over time may help in the evaluation of human-induced changes. Game fish in the project area are generally visual feeders. As such, assessing benthic drift may assist in determining the types of food resources available to fish species. Therefore, drift sampling in tributaries to the Rocky Reach Reservoir would provide additional data on the benthic invertebrate species