8106

• UCREFRP Catalog Number: 8106
• Author: Anderson, R. M.
• Title: Riverine Fish-Flow Investigations.
• USFW Year: 1998.
• USFW - Doc Type: Fort Collins, Colorado.
• Copyright Material: NO

Table 3. Means of inflection points (cfs) for the seven variables (n in parenthesis), and
results oft-test for differences. P(T<=t) for two-tail is given if alpha is <=;;0.1 is 90%.
Higher significance is indicated when alpha <=0.05 (95%), alpha <=0.01 (99%), or alpha
<= 0.001 (99.9%).

WIDE DPTH VEL WETP STG WDR AREA
Strata Cfs efs Cfs efs efs Cfs Cfs
6(11) 80 123 109 80 97 93 105
8 (19) 93 83 82 93 87 66 111
6to 8 Ns 0.001 0.003 Ns Ns Ns Ns
WIDE DPTH VEL WETP STG WID AREA
Strata (ft) (ft) (fUsee) % (ft) Ratio (sq ft)
6(11) 154 0.54 1.7 47% 0.86 414 70
8 (19) 172 0.47 1.3 47% 0.82 488 83
6 to 8 Ns Ns Ns Ns Ns Ns Ns

Inflection Point Analysis

A single cross section was selected for those riffles with more than one cross

section so that an individual riffle would not be over represented. A total of 48 cross

sections were done on 30 different riffles. Appendix Tables 1 and 2 give the inflection

point data for all 48 riffles.

The riffle variable with the lowest mean inflection point was width/depth ratio (79

cfs) while the variable with the highest mean (Ill cfs) was wetted area (Table 4-A). The

mean of the inflection points for width, depth, velocity and stage were similar at 83, 101,

93 and 92 cfs, respectively. The grand mean for the inflection points for riffles was 93.1

cfs. It was felt that the grand mean was the most unbiased estimator of the minimum

flow required to maintain riffle habitats. This flow is used as a standard for comparisons

with other habitats.

The mean of the inflection points was greater than the median (50% percentile)

for width, stage, width/depth ratio and area, but less than the median for depth and

velocity. Flows of 125 cfs would equal or surpass the inflection points for all variables

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