9708

• UCREFRP Catalog Number: 9708
• Author: Grand, T.C., S.F. Railsback, J.W. Hayse and K.E. LaGory.
• Title: A physical habitat model for predicting the effects of flow fluctuations in nursery habitats of the endangered Colorado pikeminnow ‎(Ptychocheilus lucius)‎.
• USFW Year: 2006.
• USFW - Doc Type: River Research and Applications
• Copyright Material: YES

FLUCTUATING FLOWS AND BACKWATER HABITATS

1133

Invertebrate model sensitivity anal.vsis

We conducted a sensitivity analysis on the food availability model, to (1) test whether the model resulted in
reasonable invertebrate densities under conditions representative of Green River backwaters and (2) examine the
sensitivity of the model to the flushing calibration parameter,L We conducted the analysis on both backwaters 5 and 6
to determine whether a single value of,fc could be reasonably applied to backwaters differing in size and topography.
We generated 100 predictions of the density of invertebrates available for consumption by fish, dj, from all
possible combinations of three parameters and variables:

1. The magnitude of within-day flow fluctuations (five levels of fluctuation, ranging from 0% to 40% variation
around the daily mean flow; see below);
2, Mean daily backwater temperature (four scenarios generated by varying the date on which the simulations were
run; see below); and
3. Ie (five values ranging from 0 to 1.0),

Using the main stem base flow data measured at the Jensen gauge in 1994 (Figure 4a), we crcated five flow
scenarios that had a single sinusoidal cycle of hourly flows each day (as Green River flows typically do), The
scenarios had daily minimum and maximum flows that were 0, 10, 20, 30 and 40% less than and greatcr than
the daily mean (Figure 4b), Observed flow variation during this time period ranged from 0.4% to 13.4% around the

(a) 400 June 1 to January 1
I

-
rn
;;-- 300
E
-
~
.2 200
LL
~

~1oo
c:
as
CD
:a: 0
1-Jun 1-Jul

Base Flow period

1-Aug 1-Sep 1-0ct 1-Nov 1-Dec 1-Jan
Date

(b)

-0%
--10%
--20%
-30%
~ -40%

40~ ~

60

80

July 5

-
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E
-
==
.2
LL

20

o

o 2 4 6 8 10 12 14 16 18 20 22
Hour

Figure 4, (a) Mean daily flow (m3, S-I) as measured al the Jensen gauge from] June ]994 to ] January 1995, (b) Sample flow fluctuation
scenarios for 5 July ] 994, corresponding to 0, 10, 20, 30 and 40% variation around the observed mean daily flow

Copylight (e 2006 John Wiley & Sons, Ltd,

River Res, Applic, 22: ]] 25-1142 (2006)
DOl: IO,1002lrra