9433

• UCREFRP Catalog Number: 9433
• Author: Anderson, R.
• Title: Riverine Fish Flow Investigations.
• USFW Year: 2002.
• USFW - Doc Type: Federal Aid Project F-288-R5,
• Copyright Material: NO

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

25000

20000

1997 -
16,400 cfs

-
CI)
't 15000
-
~
o
Ii:
~
m 10000
0..

1998 -
10,400 cfs

2000 -
9,830cfs

~

5000

1999 -
9,980 cfs
& Median

o
o

0.1

0.2

0.3

0.4

0.9

0.5

0.6

0.7

0.8

1

Exceedence Frequency

Figure 2. Peak flow during the study period at the Maybell gage with exceedence frequency- for
the period of record.

Minimum flows recorded at the Maybell gage for 1997, 1998, 1999,2000 and 2001 were
320 cfs, 115 cfs, 166 cfs, 30 cfs and 50 cfs, respectively. The 86 year median (50% exceedence
flow) minimum flow is 126 cfs (Figure 3). The 2000 minimum flow of30 cfs was exceeded in
93% of the years, and the 2001 minimum flow of 50 cfs was exceeded in 83% of the years for
the period of record (Figure 3). Flow did not drop below 93 cfs in 1998 and 1999, but flow was
less than 93 cfs in 34 days in 2000 and 17 days in 2001.

Two consecutive years of low flow may have more significant and lasting impacts on the
aquatic community (carrying capacity) than a single low flow year. Again, using the 93-cfs
reference flow (Modde et alI998), flow was less than 93 cfs for 0 days in 1997, 2 days in 1996,
o days in 1995. In 1994, the minimum flow was 8 cfs and flow was less than 93 cfs for 73 days
that year. Presumably habitat was severely restricted in 1994 and there were impacts to the fish
community. The four-year interval between 1994 and the start of sampling in 1998 may have
been enough time to allow the fish community to adjust back to a carrying capacity based on
physical habitat availability provided by normal base flows. There were two days of flow below
93 cfs in 1996 and these were 79 and 88 cfs. In 2000 flow had not been below 93 cfs for the
previous three years. However, 2001 was a low flow year that immediately followed a low flow
year (Figure 3).

5