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<br />would have been prescribed for the aquatic system alone. <br /> <br />Failure to consider the full range of temporal variability in hydrologic regimes stems <br /> <br />from a lack of appreciation for the multi,faceted nature and inherent complexity of hydrologic <br /> <br />regimes, and from the inability of commonly-used statistical tools for to characterize <br /> <br />hydrologic data into biologically relevant attributes. Fortunately, the role of temporal <br /> <br />,',. <br /> <br />hydrologic variation in ecosystem structure and function is becoming better understood, <br /> <br />through efforts such as Poff and Warde (1989)which'highlighted the significance of streariih~ '. <br /> <br />fif,.::;!i'ft <br /> <br /> <br />variability and predictability in the structuring of lotic communities. The ecological <br /> <br />{~"::~.-:>.- <br /> <br />significance of the rate at which water conditions change has been illustrated by many authors: <br />"':. <br />';m~;" <br />such as Rood and Mahoney (1990) and Bain etal. (1988), and the roieof seasonal flood pulSes ,,' <br /> <br /> <br />has been articulated by Junk et aI. (1989), among others. The rates of Water flow and' ."..J'j;JfiJJ;ir~\ <br /> <br />:,,,~,., . <br />fluctuation are important influences on habitat conditions because they influence water <br /> <br />chemistry and temperature, and the morphology of river channels as well. <br /> <br /> <br />Collectively, the biohydrologic research conducted to date suggests that the full rang::;"! <br /> <br />'f .~ <br /> <br /> <br />',--.>, <br /> <br />of natural intra- anddnter-annuaLvariatioIYof'hydrologic regimes is necessary to sustain th~?m <br /> <br /> <br />native biodiversity and evolutionary potential of aqUatic, riparian, and wetland ecosysteriIs:'d~ , . <br /> <br /> <br />This emerging paradigm is supported by numerous statements in the recent ecoIOgicalli~;"f'u ,\ <br />",'_'- '~~~:,z;jS):,,:~ <br />about the necessity of protecting or restoring " ilatural " hydrologic regimes (see for e~pig1~:.;,;~~"'0 <br /> <br />Sparks 1992; National Research Council 1992; Doppelt et al. 1993; Noss & Cooperridei=~i~~i:f <br /> <br />",.-"f <br /> <br />and Dynesius & Nilsson 1994). For instance, Sparks (1992) stated that rather than optiihiiffi:. <br /> <br />-,;.,~ <br />water regimes for one or a few species, "a better approach is to approximate the natural fRlw-' <br />. .,,~t lo-' <br /> <br /> <br />regime that maintained... the entire panoply of species. . <br /> <br />4 <br /> <br />-;~;~::.'-' <br />