BOARD02590

• Board Meeting Date: 1/27/2004
• Description: ISF Section - Instream Flow Appropriations - Spring Creek
• Board Meetings - Doc Type: Memo

recommendation of 5.3 cfs. The winter flow recommendations, which meet 2 of 3 criteria and
are within the accuracy range of the R2CROSS model range from 3.0 cfs to 2.1 cfs (See Table
1 ). Averaging the winter flow recommendations within the accuracy range of the model results
in a winter recommendation of 2.6 cfs. It is our belief that recommendations that fall outside of
the accuracy range of the model, over 250% of the measured discharge or under 40% of the
measured discharge may not give an accurate estimate of the necessary instream flow required.

Hydrologic Data

After receiving the cooperating agency's biologic recommendation, the CWCB and BLM staff,
conducted an evaluation of the stream hydrology to determine if water was physically available
for an instream flow appropriation. Although there is a substantial amount of streamflow gage
data available for the Uncompahgre Plateau and Glade Park, most of this data is severely
impacted by diversions and irrigation use. This situation makes it difficult to estimate the natural
flow regime for the watersheds on the Plateau. Without specific gage data to evaluate, the next
best approach is a regional equation that estimates annual flow characteristics. The USGS has
developed regional equations (Estimation of Natural Streamflow Characteristics in Westem
Colorado, Water Resources Investigations Report 85-4086, 1985) that apply to the Uncompahgre
Plateau and Glade Park based on basin drainage area, mean annual precipitation, mean basin
elevation and mean basin slope. The report "Uncompahgre Plateau and Glade Park Annual
Hydrograph Estimation" in Appendix C, explains staff's water availability analysis in more
detail. Table 2 below displays the estimated stream flow of Spring Creek.

Table 2: Spring Creek estimated streamflow.

Janua
0.87

Februa
1.9

March
2.7

riI
41

M,
150

June
69

J"'
3.5

Au ust
1.3

Se tember October November December
1.1 1.1 1 0.96

Spring Creek Estimated Stream Flow

6
5
4
tl 3
2
1
o

c^,

eo5

MAR

Am

MA'

cC'

u

ACG

see

OCT

,ov

D5C

Month

Table 2 shows that the summer flow recommendation of 5.3 cfs is available from April 15'
through June 30th. Table 2 also shows that the winter flow recommendation of 2.6 cfs is only
available from July 15' through July 315'. The winter flow recommendation was further reduced
to 0.9 cfs for the time period of August 15' through March 315' based on limited water
availability.

-4-