4-80CW092 Supplemental Data

• Case Number: 80CW0092
• Stream Name: Slate River
• Watershed: Gunnison
• Water Division: 4
• Water District: 59
• County: Gunnison
• Instream Flow App - Doc Type: Supplemental Data

mean flow in 1971-80 to the rnean �low in 1941-50 was determined.
Z'hese ratios �ere then applied to the Slate River data to estimate
the 1971-80 flows (Table 2). The CWCB filings exceed the mea�
flows in November, January, and F'ebruary. If the additional
irnpact of 42.55 cfs condi�tional rights (excluding those on
Washington Gulch) is considered, with perhaps 15o consumptive use,
the whole period from September to March could be below t7ie
instream flow.
[�iON �!'H
O
N
D
J
F
M
A
M
J
J
A
S
SL1�7'E RIVER
1941-50 (CFS)
26.9
21.0
14.3
10.6
9.5
12.7
122
536
621
204
47.2
22.3
TABLE 2
RATIO
1971�-80 TO 1941-50
.940
.915
.953
.957
.944
1.115
.789
.817
1.027
1.18U
1.009
1.039
ESTII�IATED FLOWS MEAN AMOUNT
1971-80 ABOVE CWCl3 FILIN�
25.3
19.2
13.6
10.1
9.0
14.2
96.3
438
638
241
55.7
23.2
2.3
-3.8
1.6
-1.9
-2.0
2.2
73.3
415
615
217
32.7
0.2
Alternativ�ly, consider the effects on the Slate River flows
if all irrigation rights since 1942 were developed fully and if
all non-irrigation rights (conditional and absolute since 1942)
are developed at different levels of consumptive use. Rights on
Washington Gulch are excluded since the gage was located upstream
of VJashington Gulch, but Slate river rights downstream frotn the
gage are izicluded. The resulting figures show the maximum effect
at the mouth of the Slate, assuming no tributary inflow below Coal
Cr�ek.
The irrigation rights since 1942 total 73.70 cfs. If return
flow is estimated at 35°s, then the maximum depletion would be 47.9
cfs. Assume that depletions are proportional to consumptive use
for pasture grass in Gunnison, and that there is sufficient water
to cover the znaximum de�letion (Table 3).
MON`I'H
A
N1
M�t�lORANDUNi
CONS. USE
IN INCHES
.29
1.74
TABLE 3
$ OF
MAX
.09
.52
-2-
DEPLETION (CFS)
4.3
24.9
April 22, 1985