BOARD02056

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

UncoIDnahu:re Plateau and Glade Park Annual Hvdro!!ranh Estimation

Altho gh 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
diftic It to estimate the natural flow regime for the watersheds on the Plateau. Without specific gage data
to eva uate the next best approach is a regional equation that estimates aIlllUal flow characteristics. The
USGS has developed regional equations (Estimation of Natural Streamflow Characteristics in Western
Color do Water Resolli'ces Investi.ations Reoort85-4086. 1985) that apply to the Uncompahgre Plateau
and G ade Park. The equation that applies is as follows:

Q'M ~ 9,7xI0.2(Ao888)(Ebl.74)(1.98)(365)
Qanll = mean annual volwne in acre - feet
A= drainage area in square miles
Eb ~ (mean basin elevation - 5000)/J 000

In order to verify the validity of this equation, the results were checked against gages that provided
estimates of the natural annual discharge. Three gages were located that provide a diversion free estimate
of a natural hydrograph.

Spring Creek near BeaveT Hill: Period of record; 1978 -1980
Potter Creek neaT Olathe: Period ofrecord; 1980
HayP ess Creek above Fruita Reservoir #3: Period of record; 1984 - 1987

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

Sprin 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 P ess Creek above Fruita Reservoir #3:
Mean annual gage volume: 575 ac-ft
Annual volume regional equation: 625 ac-ft