Wyoming drought-free since late June
by Jim Fahey, Wyoming NOAA Hydrologist
November 4, 2009
Here is the latest information on drought conditions across Wyoming (as of October 30th), with a review of water year 2009.
- All of Wyoming continues to be hydrologic drought-free since late June.
- Normal to above normal precipitation totals for rangelands/basins across almost all of Wyoming for water year 2009 (October 2008 - September 2009.
- Near normal to above normal mountain snowpack averages across Wyoming for water year 2009.
- Above normal streamflows during the spring runoff--with higher than normal flows lasting well into summer 2009.
- Reservoirs across Wyoming continue to maintain and/or increase "carryover" storages during water year 2009.
Three key ingredients define the overall drought picture for Wyoming:
Precipitation across Wyoming’s pasturelands/rangelands during the water year 2009 (October 2008 - September 2009) was normal to above normal for almost all of Wyoming. Precipitation across the major river basins across Wyoming was also near normal to above normal. Specifically, precipitation averages across Wyoming’s major watersheds varied from 94 to 118 percent of average during water year 2009.
Reservoir storages at the end of water year 2009 at a majority of the major reservoirs continue to be above water year 2008 averages. Most importantly, storages at the big reservoirs along the North Platte River have continued to see sharp gains during water year 2009. Seminoe and Pathfinder reservoirs ended up at 60 to 70 percent of capacity by the end of the water year.
Streamflows across Wyoming during the runoff and even into the late summer months were above to well above normal. What is most impressive, was not just the amount of discharge in Wyoming’s streams and rivers, but how long the above-average streamflows lasted. For instance, the Wind River had above normal flows that began in late May--and lasted into late July! This trend was seen in many streams and rivers across Wyoming in 2009.
Snow water equivalents (SWEs) for water year 2009 were near normal to above normal across almost all major watersheds across the state.
Overall Drought Picture and What Does the Future Hold?
Wyoming is doing very well in keeping hydrologic drought conditions at bay. A cool and wet summer in 2009 at many rangeland locations across Wyoming enabled reservoirs to retain and/or to gain more "carryover" storage by the end of the water year--as there was less demand put upon surface water resources by irrigation and farming in 2009. A cool and wet summer also allowed further recharge in soil profiles and/or in ground water aquifers across Wyoming’s watersheds. This points to the reason why Wyoming’s streamflows were not only above average during the normal runoff period---but the higher than normal discharges continued well into the summer.
Wyoming’s mountain snowpack averages were near normal to above average for the second straight water year. However, late fall and early winter snowpack averages across Wyoming during the past two water years have continued to be below average. It hoped that with the soil moisture "recharge" that has continued into water year 2009 (and even into early water year 2010), any late fall/early winter snowpack will be retained and not lost to now "wet" antecedent soil conditions.
Bottom line is that current precipitation, water supply, and streamflow trends are definitely keeping the momentum going with keeping another long-term hydrologic drought away from Wyoming. Wyoming is the 5th driest state in the country--so drought is always ‘knocking-on’ on Wyoming’s back door.
For the complete drought report with graphics (in .PDF format) please go to:
For additional drought graphics and information, please refer to: