Note: This publication is currently undergoing major revisions. The current publication will be replaced with a new publication based on stakeholder requirements and scientific advances. We expect to begin sharing details on this soon. If you have input on content, format, or publication frequency at any time, please contact us at firstname.lastname@example.org.Great Basin Water Supply Outlook, January 1, 2009
After a warm and dry start to Water Year 2009, December precipitation in the Great Basin
totaled 131% of average. These much above average totals greatly improved snow conditions throughout
all the northern basin with indexed snow totals of 90% in the Weber and Ogden basins, 87% in the Provo
basin, 87% in the Bear River basin and 95% in the Six Creeks basin. Antecedent soil moisture
grids from our ESP
model however indicate below to much below average soil moisture conditions which tend to lower
the April through July volume forecasts. Water year precipitation in the overall Great Basin
was 99% of average. However in the headwater regions where most volume is produced during the runoff season,
values are below average.
Weather guidance from National Weather Service models are predicting generally dry conditions through mid month.
Longer range predictions from NOAA's Climate Prediction Center indicate equal chances of wet or dry conditions
through the spring of 2009. A forecast La Nina, released from CPC January 8th, based on current observations,
recent trends and model forecast, La Nina conditions are likely to develop and continue into the
Northern Hemishphere Spring of 2009.
Volumetric forecasts were weighted slightly lower due to dry soil condition, ranging from 78% of average
on the Weber River at Echo to 95% at both Big and Little Cottonwood Canyons near Salt lake City.
*Median of forecasts within each basin.
Bear Basin Conditions
As of January 1st, conditions across the Bear River basin are slightly below normal. Snowpack
conditions are currently 87% of average. Monthly precipitation was 122% of average while seasonal numbers
were 96% of average. Stream flow estimates for the Bear at the Utah/Wyoming border were 66% of average for
December showing much below average baseflows, a good indication of low soil moisture conditions. Forecasts
in the Bear River Basin ranged from 83% at Blacksmith Fork near Hyrum to 90% of average at Bear near
Montpelier below Stewart Dam.
As of January 1st, conditions across the Weber and Ogden basins are slightly below normal. Monthly
precipitation was at 120% of average and seasonal precipitation summed to 90% of average. Snow water
equivalency is 90% of average. Estimated stream flow for the Weber at Oakley during December were 89% of
average. The April through July volume forecasts range from 82% of average at Weber River at Gateway
to 90% of average at East Canyon Creek Reservoir near Morgan.
As of January 1st, conditions across the Six Creeks basin near Salt Lake City are slightly below normal.
Monthly precipitation for December was 139% of average and seasonal precipitation summed to 105% of average.
Current snowpack conditions are 95% of average. Observed stream flow for Mill Creek near Salt lake City were
below average for December at 82% of average. April through July volume forecasts range from 82% percent of average
at Emigration Creek near Salt Lake City to 95% percent of average for Big and Little Cottonwood Canyon Creeks near
Salt Lake City.
As of January 1st, conditions across the Utah Lake basin are slightly below normal. Monthly precipitation
for Utah Lake Basin was 135% of average and seasonal precipitation totalled at 96% of average. Observed stream
flows for Spanish Fork during December was 125% of average due to heavy rainfall. Currently the indexed snow
for the Utah Lake Basin is 90% of average. December stream flow for the Provo at Woodland was 90% of average.
Forecasts for Utah Lake ranged from 81% at Spanish Fork near Castilla to 90% of average for Provo at Hailstone.