EF Dry Creek Appendices

• Case Number: 05CW0151
• Stream Name: East Fork Dry Creek
• Watershed: Uncompahgre
• Water Division: 4
• Water District: 41
• County: Montrose
• Instream Flow App - Doc Type: Supplemental Data

Table I' Data

PartY Date Q 250%-40% Summer (3/3) Winter (2/3)
BLM 06/03/2003 1.57 0.6 - 3.9 3.64 1.58
BLM 10/14/2003 0.30 0.1-0.7 8.76(1) 0.82(1)
BLM 11103/2004 1.39 0.6 - 3.5 ? 0.50(1)

BLM "" Bureau of Land Management DOW = DIVISion ofWildhfe
(1) Predicted flow outside of the accuracy range of Manning's Equation. ? = Criteria never met in R2CROSS Staging Table.

Biologic Flow Recommendation
The summer flow recommendation, which meets 3 of 3 criteria and is within the accuracy range
of the R2CROSS model is 3.6 cfs (See Table I). The winter flow recommendation, which meets
2 of 3 criteria and is within the accuracy range of the R2CROSS model is 1.6 cfs (See Table I).
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 Western
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 East Fork Dry Creek.

For this reach, the synthetic hydrograph shows that the summer flow recommendation of 3.4 cfs
is available only from April I to June 30. The summer flow recommendation was reduced to
1.60 cfs for the time period of July I through July 31 based on limited water availability. The
winter flow recommendation of 1.6 cfs is only available March I through March 3 I. The winter
flow recommendation was reduced to 0.6 efs for the period of August I to February 28 based on
limited water availability.

Table 2: Estimated Stream Flow on West Fork Dry Creek:
Jan Feb Mar Apr May Jun
(cts) 0.7 1.4 2.0 31.0 113.0 51.9

Jul
2.7

Aug Sep
1.0 0.8

Oct
0.8

Nov Dee
0.8 0.7

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