1-02CW373 Supplemental Data

• Case Number: 02CW0373
• Stream Name: South Fork South Platte River
• Watershed: South Platte
• Water Division: 1
• Water District: 23
• County: Park
• Instream Flow App - Doc Type: Supplemental Data

Table 1: Data
Party
Date
Q
250 % -40%
Summer (3/3)
Winter (2/3)
TU
9/26/00
13.0
32.5 - 5.2
15.3
4.0(1)
CWCB
11/13/01
10.4
25.9 - 4.1
4.6
4.4
TU = Trout Unlimited DOW = Division of Wi dlife CWCB = Colorado Water Conservation Board
(1) Predicted flow outside of the accuracy range of Manning's Equation. ? = Criteria never met in R2CROSS Staging Table.
Biologic Flow Recommendations
TU recommended a 16 cfs summer flow and a 4.0 cfs winter flow based on their September 26th,
2000, data collection efforts.
Staff reviewed the data collected by TU and decided to collect additional data sets. The summer
flow recommendation, which meets 3 of 3 criteria and is within the accuracy range of the
R2CROSS model is between 15.3 and 4.6 cfs. Averaging the two summer flow
recommendations within range results in a 10.0 cfs recommendation. The winter flow
recommendation which meets 2 of 3 criteria and is within the accuracy range of the R2CROSS
model is 4.4 cfs (See Table 1).
Hydrologic Data
After receiving the cooperating agency's biologic recommendation, the CWCB staff conducted
an evaluation of the stream hydrology to determine if water was physically available for an
instream flow appropriation. There are no currently operated or historically operated streamflow
gages for this reach. The closest gage CWCB staff found was the gage located on the South
Fork of the South Platte River 4.2 miles upstream on the South Fork South Platte River. The
hydrograph was derived from data collected by the USGS stream gage for the South Fork South
Platte River near Fairplay, CO (ID #06694400), which has a drainage area of 50.3 square miles
(See Gage Summary in Appendix C). The period of record for this gage was 1978 to 1980, the
period of record used by staff in their analysis was 1978 - 1980, or two years of record. Table 2
below displays the estimated flow of South Fork South Platte River, in terms of a percentage of
exceedence based on the above gage.
Table 2:
South Fork South Platte
Exceedences Janua
1%
5%
10%
20%
50%
80%
90%
95%
99
Februa
March
Aoril
Ma
June
Jul
August September October November December
6.8
6.6 r'
6.5
- °.12
-' 127
251
140
44
25
15
- 11
- 9
6.8
6.6
6.5.
9.95 -
113.4
235.5
103.5
-' 39.35
21
15
11
9
6.8
6.6
6.51.
9
89.1
218
91.4
'' 36.7 -
19
15
11
9
6.8
6
6.5
7.2
43.4
190
-- -77.6
29.4
16
11
9.8
-
9
6
6
4.6:
6.5
14.5
115
'- 49.5 -
20.5
9.9
9.8
'9
6.8
6
5.5 .;
4.5
.4.6
' 10
-':76
`...31.6. -
12
8,5
6.9
7
6
6
5.5 `.•
4.49
4.4
7.2
- 69
'.. 25
'' 9.93
8
6.6
7
6
V
6
5.5
4.2
4.3
5
65.5
22
9.46
7.9 '-
6.6 -.
6.5
�.
6
5.5
5.5
4.08
4.1
5
62.7
17.93
'- 8.8
7.6
6.4
6.5
6
However, the proposed instream flow segment would also receive additional inflow from the
Twelvemile Drainage Basin which provides inflow below the gage. The Twelvemile Drainage
Basin is approximately 30 square miles. Table 3 below displays the estimated flow of South
Fork South Platte River, in terms of a percentage of exceedence based on the above gage, plus
the additional inflow from the Twelvemile Basin.
5