United States Department of Agriculture Forest Service Intermountain Forest and Range rirnent Station m, UT 84401 General Technicai Report INT-138 May 1983 Platts, William S.; Megahan, Walter F.; Wshall, G. Wayne. Methods for evaluating stream, riparian, and biotic conditions. GeTL. Tech. Rep. INT-138. Ogden, UT: U.S. Department of Agriculture, Forest Semice, Intermountain Forest and Range Experiment Station; 1983. 70 p. ERRATA Page 16 Figure 11, first line A channel embeddedness of -.4 instead of 2. Page 23 Line 13, 1st column Elevation instead of evaluation Page 25 Figure 20 Photograph is upside down Page 30 Equation 7 Eliminate the last parenthesis Page 31 Equation 17 The first and i&t brackets in the denominator are backwards Page 32 Line 52, 1st Column -28.3 instead of 20.3 Page 33 Table 12, line 2 6-10 instead of <6-10 Page 57 First equation should be WILLIAM S. PLAITS is a Research Fishery Biologist for Most stream habitat evaluation techniques currently in the lntermountain Station at Boise, ldaho. He received a use today have not been tested to determine their validity in B.S. degree in conservation-education in 1955 from ldaho describing conditions and have been designed to optimize State University, a M.S. degree in fisheries in 1957 and a time rather than accuracy. The purpose of this report is to Ph.D. degree in fisheries in 1972 from Utah State University. further standardize the way physical and biological attributes From 1957 through 1966, he worked as a Regional Fishery are measured and quantified and to shed light on the Biologist and Supervisor in Enforcement with the ldaho Fish strengths and weaknesses of those attributes. This report and Game Department. From 1966 through 1976, he was discusses some of the environmental parameters that best the ldaho Zone Fishery Biologist for the USDA Forest Serv- measure and describe conditions existing in aquatic ice, intermountain Region and consultant to the Surface ecosystems. The precision and an estimation of the accu- Environment and Mining (SEAM) program. He has been in racy that can be expected when measuring many of these his present position since 1976. conditions are given. E MMEGAHAN is a Principal Research Hydrologist and Leader of the lntermountain Station's Nonpoint Source Pollution Research Work Unit in Boise, Idaho. He holds B.S. ar,d M.S. degrees in forestry from the State University of New York, College of Forestry at Syracuse University, and a We are grateful to the Library Executor of the late Sir Ph.D. degree in watershed resources from Coiorado State Ronald A. Fisher, to Dr. Frank Yates, and the Longman University. He served as Regional Hydrologist for !he inter- Group Ltd., London, for permission to reprint our table -19 mountain Region of the Forest Service in Ogden, Utah, from their book Statistical Tables for Biologicaf, from 1960 to 1966 and has been in his present position Agriculture, and Medical Research (6th ed., 1974) and to since 1962 the American Society of Civil Engineers for permission to reprint our table 4 from their publication Sedimentation G. WAYNE MlNSHALL is Professor of Zoology at ldaho Engineering edited by Vito A. Vanomi. State University, Pocatelio, Idaho. He received his 5.S. degree in fisheries management in 1961 from Montana State University and his Ph.D. degree in zoology in 1965 from the University of Louisviile. He was a North Atlantic Treaty Organization (NATO) postdoctoral fellow at Fresh- water Biological Association Windemere Laboratory from 1965 through 1966. He joined the staff at ldaho State Univer- sity in 1966 where he has pursued a teaching and research program in stream ecology. The use of trade, firm, or corp~rationnames in this publication is for the information and convenience of the reader. Such use does not constitute an official endorse- ment or approval by the U.S. Department of Agriculture sf any product or service to the exciusisn 0%others which may be suitable. CONTENTS Introduction ...................................Page Background ................................. Problem .................................... Purpose .................................... Solution .................................... Study Sites ................................... Aquatic Habitat .............................. Fisheries ................................... Sampling Design ............................... Bias. Accuracy. and Precision .................. Population Parameters ........................ Standard Error ............................... Confidence Limits ............................ Sample Size ................................ Transect System ............................... Transect Cluster ....................... .. ... Accuracy and Precision of Measurements ........... Stream Habitat Evaluation ....................... Water Column ............................... Channel Morphology .......................... Streambank ................................. Stream Bottom .............................. Riparian Zone ................................. Streamside Cover ............................ Vegetation Use by Animals ..................... Herbage Production and Utilization .............. Vegetation Overhang .......................... Habitat Type ................................ Fish Population Evaluation ....................... Electrofishing ................................ Toxicants ................................... Explosives .................................. Direct Undenrvater Observation .................. Macroinvertebrate Analysis ....................... Sampling Strategy ............................ Sampling Methods ............................ Sample Processing ........................... Data Treatment and Interpretation ............... Biological Indexes ................... ... ..... Conciusions ................................... Publications Cited .............................. Appendix 1 The t Distribution ................... Appendix 2 Transect Spacing ................... Appendix 3 Examples of Accuracy. Precision. and Confidence Intervals ................. Appendix 4 Mathematical Proof of Needed Stream Depth Measurements ................ Appendix 5 Stream Habitat and Fishery Rating Variables that Failed to Show Promise . Appendix 6 The POPEST Computer Program ...... Appendix 7 Tolerance Quotients of Aquatic Macroinvertebrates .................. Appendix 8 A Key to Community Tolerance Quotients .......................... Amendix 9 Biotic Index for Chandler's Score ...... Met hods For Evaluatina Stream, Riparian, and Biotic Conditions William S. Platts Walter F. Megahan G. Wayne Minshall INTRODUCTION Problem Background Difficulties arise in developing accurate, complete The past decade has seen an increase in the number of studies methodologies because of problems encountered in attempting to evaluating the status and potential of streams as habitats for quantitatively determine the true state of an aquatic system (Platts aquatic organisms. Stream inventories, monitoring, habitat 1976). In addition, aquatic specialitists commonly collect their data research studies, assessments, channel and flow condition evalua- during the warmer months of the year (from June through tions, and classification are used to evaluate this potential. The September), when access, streamflow, and water quality are opti- success or failure of these stream studies depends on the suitabili- mum for aquatic observation. Aquatic habitats and their biotic ty, comprehensiveness, precision, and accuracy of measurements communities are seldom evaluated during periods of floods, used to obtain the data upon which final interpretations are based. annual high flows, extreme low flows, anchor ice buildup, ice These interpretations have been used by planners and decision- flow scouring, debris jam breakup, or sudden toxic flushes. makers on the assumption that they were derived from Because some important limiting factors, inside or outside the measurements that truly described stream habitat conditions and system, usually exert their effects during periods of no data col- the resulting biotic community. lection, true existing states, or the changes of these states over Within the past decade measurements of stream habitat condi- time in the stream have rarely been determined. A valid tions, such as velocity, depth, and cover, have been incorporated understanding of the mix of environmental conditions that control into models designed to indicate fish standing crops and to assist the fishery, therefore, eludes us. in evaluating impacts from land management activities. Binns Platts (1974, 1976) demonstrated that while masses of (1979) developed a Habitat Quality Index to predict trout standing multivariable environmental data can be gathered during these crops in Wyoming streams. The USDI Fish and Wildlife Service warmer months, complete and reliable information still is lacking. (Cooperative In-stream Flow Group) uses a cluster of aquatic His study also demonstrated that additional descriptive variables, habitat descriptors in a predictive model to quantify the effects of not yet discovered, are needed if adequate quantification of stream change in streamflow on fish survival. Their Aquatic Habitat condition is to be gained. In today's methodologies (where the Evaluation Team also has developed an Aquatic Habitat Evaluation "state-of-the-art" lacks refinement and the form often is directed Procedures model (HEP) and Habitat Suitability Index model by expediency and low cost), the observed physical, biological, (HSI) for