BOARD00088 ‎(2)‎

• Board Meeting Date: 11/14/2006
• Description: WSP Section and ISF Section - Arkansas River ISF Appropriation
• Board Meetings - Doc Type: Hearings

suckermouth minnow (Phenacobius mirabilis) historically inhabited this reach of the Arkansas River but
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have been absent from recent fishery surveys. Flathead chub (Platygobio graci/us) and suckermouth
minnow (Phenacobius mirabi/is) have been id~ntified by the DOW and several other state and federal
agencies as "species of greatest conservation need". As directed by Colorado's 2005 Comprehensive
Wildlife Conservation Strategy (CWCS), now is involved in developing conservation and management
plans for these species. The intention ofthese plans is to increase populations and distributions ofidentified
species, thereby assisting in the long-term persistence of each species. The success of such plans could
potentially curtail the need for federal listing of these species under the Endangered Species Act (ESA).
These species are not currently federally listed.

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Instream Flow Sune\' Data
The DOW, in September of 2005 and March of 2006, collected stream cross section information, natural
environment data, and other data needed to evaluate the proposed 100 cfs instream flow recommendation.
The stream cross section data was analyzed using the R2CROSS program. The R2CROSS output was
evaluated using the methods described in Nehring (1979) and. Espegren (1996). DOW collected physical
data at four different cross-section locations at three different discharges (see attached map). The observed
flows ranged from a high of 260 cfs to a low of 58 cfs. The width of the Arkansas River at the four study.
sites ranged from 160 feet to 132 feet.

X-Section Locations
Data relating to the individual x-sections are discussed below:

. Site #1 is located approximately Yo. mile downstream of Pueblo Dam. The bank full width ofthis x-
section was 151 ft and had a hydraulic slope of less than 1 %. Data collection flows at this site
included flows of 58, 89, 155 and 260 cfs.
. Site #2 is located near the eastern end of Lake Pueblo State Park, approximately 2 miles downstream .
of Pueblo Dam. The bank full width of this x-section was 132 ft and had a hydraulic slope ofless
than I %. Data collection flows at this site included flows of 92, 155, 178 and 264 cfs.
. Site #3 is located approximately 100 yards down-stream of the railroad bridge crossing the Arkansas
River near Reservoir Road. The bank, full width of this x-section was 160 ft and had a hydraulic
slope ofless than I %. Data collection flows at this site included flows of 85, 155, 174 and 252 cfs.
. Site #4 is located approximately ~ mile upstream of the confluence with Fountain Creek. The bank
full width of this x-section was 141 ft ~d had a hydraulic slope of less than 1 %. Data collection
flows at this site included flows of 82, 136 and 223 cfs.

DOW evaluated the stream flow hydraulics and channel characteristics which occur at the proposed 100 cfs
flow recommendation, see Table 1 below.

Table 1: Stream Flow HydrauHes and Channel Characterlstles at 100 efs
X-section % Wetted Perimeter Avera~e Depth
#1 - Below Reservoir 69.8% 0.89 feet
#2 - Lower State Park 72.0% 0.76 feet
#3 - Below RR-Xing 75.9% 0.53 feet
#4 - Above Fountain Ck 61.3% 0.53 feet

Average Velocity
1.06 ftls
1.33 ftls
1.54 ftls
2.19 ft/s

A 100 cfs instream flow would provide:

. Enough water to wet approximately 70% ofthe stream channel at 3 of the four x-section locations I..
and 61 % of the stream channel at X-section #4;
. An average depth of close to 0.5 feet at all four x-sections and nearly 0.9 feet at X-Section #1; and
. An average velocity of over 1.0 feet per second at all x-sections.