INSTREAM FLOW ASSESSMENTS 

 COME OF AGE IN THE DECADE OF THE 1970s 



Clair B. Stalnaker 



INTRODUCTION 



Historically, water rights could be obtained in the western United States only 

 through a state appropriation for applying the water out of the stream to some 

 "beneficial" use. Beneficial use has been defined by state law and normally has 

 included municipal, industrial, stock watering, agricultural, and mining. Stream and 

 associated riparian ecosystems, recreation, and aesthetics have only recently been 

 recognized as beneficial uses of water in some states. These water uses and several 

 others which depend on in-channel flow are often referred to as "instream uses, "and 

 their flow requirements as "instream flow needs." 



In the face of increasing water demands for energy and expanded agricultural 

 production, there has been a widespread recognition of the necessity for maintaining 

 water in the stream for such uses as fish and wildlife production, recreation and 

 aesthetic enjoyment, estuarine inflows, hydropower, and navigation. Recent 

 legislation and court decisions have pointed out the need for identifying instream 

 flow requirements and quantifying their magnitude. With legal recognition that 

 instream uses should be considered on a par with offstream uses came increased 

 demand for methodologies to supply water resource agencies and planners with 

 information to: (1) determine relationships between benefits derived from instream 

 uses and streamflow quantity; and (2) determine the optimum allocation of limited 

 fresh water resources among various instream and offstream uses. 



During the past three decades, federal and state agencies involved with water 

 resource use and management have independently been devising methodologies in an 

 attempt to address these problems. This resulted in much duplication of effort, 

 fragmented approaches, and considerable lag in acceptance of credible methods. 

 However, substantial progress for protecting instream habitat for fish and wildlife 

 was achieved during the decade of the 1970s due to two primary reasons: 



1. New environmental legislation emerged as a result of a heightened awareness 

 by the public of the growing reduction of our stream ecosystems and the 

 realization that only through legal protection would future generations be able 

 to enjoy these instream values. 



2. Stimulated by demands from the water planning community for quantitative 

 documentation of instream flow requirements, new techniques were devised 

 that produced persuasive support for the aquatic biologist's recommendations. 



This paper traces the evolution of instream flow assessment methodologies and 

 highlights the legal and institutional events which contributed to the increased interest 



The Author; Dr. Stalnaker currently serves as Leader, Instream Flow and Aquatic Systems Group, Western 

 Energy and Land Use Team, Fish and Wildlife Service, U.S. Department of the Interior, Fort Collins, 

 Colorado. His professional background also includes applied research in the state of West Virginia natural 

 resources, the FWS Cooperative Fisheries Research Unit, Utah State University, Logan, and Fishery 

 Research Specialist, Federal Aid Program, Denver, Colorado. 



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