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Last modified
1/26/2010 12:29:33 PM
Creation date
10/11/2006 10:13:12 PM
Metadata
Fields
Template:
Water Supply Protection
File Number
8062
Description
Federal Reserved Water Rights
State
CO
Basin
Statewide
Date
3/1/1995
Author
USDOC
Title
Instream Flow Incremental Methodology - A Primer for IFIM
Water Supply Pro - Doc Type
Report/Study
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<br />2 BIOLOGICAL REpORT 29 <br /> <br />'" <br /> <br />Chapter 1. The History of Instream <br />Flow Problems and IFIM <br /> <br />Instream flow methods have been developed pre. <br />dominantly by biologists and hydrologists working <br />for agencies having regulatory responsibility re. <br />lated to water development and management (Stal- <br />naker and Arnette 1976), Such efforts over the last <br />30 years have pro\ided the impetus for detailed <br />ecological studies leading to a significant growth in <br />the understanding of the relations between stream <br />flow and aquatic habitats. Most of the empirical <br />evidence gathered to date has focused on fish and <br />benthic macro-invertebrate habitat requirements, <br />with recent emphasis on the relation between <br />stream flow and woody riparian vegetation and <br />river.based recreation (Gore 1987; Orth 1987; <br />Brown 1992; Shelby et al, 1992; Scott et al. 1993), <br />Water management problem sohing has matured <br />from setting fixed minimum {lows with no specific <br />aquatic habitat benefit to incremental methods in <br />which aquatic habitats are quantified as a function <br />of stream discharge, Within this historical progres- <br />sion we also saw the application of a water budget <br />which set the stage for having the fisheries man- <br />ager be an integral part of an interdisciplinary <br />decision.making system, This chapter will review <br />the progression of circumstances and techniques <br />leading to the development of IFIM and point to- <br />ward what the future might hold, <br /> <br />Minimum Flow Standards <br />Provide Minimal Protection <br /> <br />Following the large reservoir and water devel- <br />opment era of the mid-twentieth century in North <br />America, resource agencies became concerned over <br />the loss of many miles of riverine fish and wildlife <br />resources in the arid western United States, Con. <br />sequently, several western states began issuing <br />rules for protecting existing stream resources from <br />future depletions caused by accelerated water de- <br />velopment, Many assessment methods appeared <br />during the 1960's and early 1970's, These tech, <br />niques were based on hydrologic analysis of <br />the water supply and hydraulic considerations of <br /> <br />critical stream channel segments, coupled with <br />empirical observations of habitat quality and an <br />understanding of riverine fish ecology, most nota. <br />bly the Pacific salmon and freshwater trouts. Col. <br />lectively, the e(forts led to a general class of in. <br />stream flow assessment techniques (models) <br />meant to heJp reserve a specific affioW1t of water <br />within the channel for the benefit offish and other <br />aquatic life (Wesche and Rechard 1980; Morhardt <br />1986; Stalnaker 1993), Application of these meth. <br />ods usually resulted in a single threshold or 'mini- <br />mum' flow value for a specified stream reach below <br />which water may not be withdrawn for consump. <br />tive water use. The minimum now is almost al- <br />ways less than the optimal or pristine habitat <br />condition, yet these 'reservations' of water form the <br />current basis for issuing water permits in many <br />states. See MacDonnell et aI. (1989) and Lamb and <br />Lord (1992) for recent discussions of the status of <br />stale recognition and protection of flowing water <br />for instream now. <br /> <br />Impact Analyses Lead to <br />Increased Resource Protection <br /> <br />Following enactment of the National Environ. <br />mental Policy Act (NEPAl of 1970, attention was <br />shifted from minimum flows to the evaluation of <br />alternative designs and operations of federally <br />funded water projects. Methods capable of quanti- <br />fYing the effect of incremental changes in stream. <br />flow to e\'aluate a series of possible alternative <br />development schemes were needed (Stalnaker <br />1993), This need led to the development of habitat <br />versus discharge functions developed from life- <br />stage-specific relations for selected species, that is, <br />fish passage, spawning, and rearing habitat versus <br />flow for trout or salmon Corroborating research <br />took the form of analyses correlating the general <br />well-being of fish populations (usually in tenus of <br />measured standing crop) with various physical and <br />chemical attributes of the stream flow regime and <br />its interaction with the stream channel structure <br />
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