BOARD00598

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

UnCOffiDahl!re Plateau and Glade Park Annual HvdroQraoh Estimation

Although there is a substantial amount of streamflow gage data available for the Uncompahgre Plateau and
Glad~ 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 ev<\luate the next best approach is a regional equation that estimates alillual flow characteristics. The
USGS has developed regional equations (Estimation of Natural Streamflow Characteristics in Western
Coloi~do. Water Resources Investigations ReDort 85-4086. 1985) that apply to the Uncompahgre Plateau
and Glade Park The equation that applies is as follows:

Q"" "" 9.7xl O"(A O.888)(Eb 1.74)(1.98)(365)

QatUl = mean alillual volume in acre - feet
A= drainage area in square miles
Eb ~ (mean basin elevation -5000)/1000

In or~er to verify the validity of this equation, the results were checked against gages that provided
estim*tes of the natural annual discharge. Three gages were located that provide a diversion free estimate
of a nhtural hydrograph.

Sprin$ Creek near Beaver Hill: Period of record; 1978 -1980
Potter Creek near Olathe: Period of record; 1980
Hay ~ress Creek above Fruita Reservoir #3: Period of record; 1984 - 1987

Using;the period of record for each of the gages a mean annual volwne was calculated and compared to the
result~ obtained using the regional equation.

Sprinl1 Creek near Beaver Hill:
Mean annual gage volume: 11,100 ac-ft
Annual volume regional equation: 11,300 ac-ft
Potter' Creek near Olathe:
Mean annual gage volume: 5,000 ac-ft
Annual volume regional equation: 6,000 ac-ft
Hay Press Creek above Fruita Reservoir #3:
Mean annual gage volume: 575 ac-ft
Allllual volume regional equation: 625 ac-ft

1-'