WSP03545

• File Number: 8240.200.40.J
• Description: Yampa
• State: CO
• Basin: Yampa/White
• Water Division: 6
• Date: 4/3/1995
• Title: A Method for Assessing Hydrologic Alteration within Ecosystems
• Water Supply Pro - Doc Type: Publication

these five fundamental regime characteristics for the specified time frame.

Here, we define 32 attributes divided into five major groups to statistically characterize

intra-annual hydrologic variation in a biologically relevant manner (Table 1). These attributes

provide an adequate representation of the hydrologic regime for the purpose of assessing' ,i'

hydrologic alteration. They are sensitive to common human influences such as reservoir' ;m

operations, ground water pumping, and agricultural diversions (see Table 2), and most

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Kozlowski 1984; Gustard 1984; Poff & Ward 1989;.and Hughes &James 1989 for e~

-- the IHA method incorporates hydrologic statistics that are meaningful in an ecologicai'f ~l..

context. Also, because certain streamflow levels shape physical habitat conditions withi~.. .
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channels, we.also identified hydrologic characteristics that might aid in detection of physi&l~.:r~i;;:;:
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habitat alteration in lotic systems. For example, changes in the central tendency of annuai$!"lJ:t" '
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maxima, which closely corresponds to "bankfull" streamflow conditions, might suggest' "1'~

changes in river morphology (Leopold 1994).

Sixteen of the.attributes,focuson.the.magnitude, duration, timing, and frequency ot1P~"';

extreme events,because of the pervasive influence of extreme forces in ecology (Gaines 8t. ,:.~

Denny 1994) ,and geomorphology (Leopold 1994); the other 16 attributes measure the'ce~::_ .
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tendency of either. the magnitude or rate of change of-water conditions. The rationale,'N ..;i',:
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underlying the. five major groupings- and the specific attributes included within each are, ";.~~-; '.
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described below,

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The basic,data.used in estimating all.attribntevalues aredaiiy meanwaterconditi0u5i;'.:b
(e.g., levels, heads, flow rates). The same computational strategies will work with any '~mi!(l(

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