Upper Missouri Basin
The high elevation snow pack in the Upper Missouri Basin as of
April 1 was near average. The snow pack above Toston, Montana
was 106 percent of average. The snow pack between Toston and
Fort Peck, Montana was 101 percent. The snow pack in the St Mary
and Milk river basins was 108 percent.
March precipitation was below average across the entire Upper Missouri
Basin. Basin precipitation summaries for the Missouri Basin include:
Milk St. Mary, 48 percent; Milk Canada, 44 percent; Lower Milk, 69
percent; Above Toston, 67 percent; Toston to Ft. Peck, 48 percent.
Stream flow in the Upper Missouri Basin is forecast to be near
average during the upcoming spring and summer. The St. Mary River
is forecast to have 99 percent of average April-September flows.
Runoff is expected to range around 100 percent of average for the
Missouri Basin above Fort Peck, Montana. Forecasts for the Milk
River Basin call for around 95 percent of average spring summer runoff.
Of the four major irrigation reservoirs in Montana: Lima Reservoir
had 56 percent average storage, Clark Canyon was holding 75 percent of
average water, Gibson Reservoir had 50 percent of average stored
water, and Fresno Reservoir had 41 percent of average stored water.
The major hydroelectric reservoirs in Montana (Canyon Ferry and
Fort Peck) had monthend storage in the average to below average
range; 96 and 59 percent of average water, respectively.
As indicated by the U.S. Geological long term gaging stations,
the Marias River near Shelby, Montana had an estimated 38 percent
of average runoff in March.
The high elevation snow pack in the Yellowstone Basin was mostly
average on April 1. The snow pack in the Upper Yellowstone Basin
was 108 percent of average. The snow packs in the Wind, Bighorn,
and Shoshone Basins were 99, 104, and 101 percent of average,
respectively. The snow packs in the Tongue and Powder basins were
97 and 110 percent of average, respectively.
Precipitation was average to below average in the Yellowstone Basin
during the month of March. Precipitation was about 61 percent
of average in the Wind River Basin above Boysen Reservoir, 81 percent
of average in the Bighorn Basin, and 81 percent of average in the
Little Bighorn Basin. The Powder River Basin received 69 percent
of average March precipitation. March precipitation was 91 percent
of average in the upper Yellowstone Basin (above Billings) and
only 38 percent of average in the Lower Yellowstone Basin.
Stream flow in the Yellowstone Basin is forecast to be mostly about
average during the upcoming spring and summer. Runoff at
Billings, Montana is expected to be 113 percent of average, with
a probable range between 87 and 139 percent of average. Stream
flow for the Wind-Bighorn Basin above St. Xavier, Montana is
forecast to be 106 percent of average with a probable range
of 49 to 148 percent of average flow in sub-basins. Flow in the
Tongue Basin is expected to be 104 percent of average with a
reasonably likely range of 68 to 148 percent of average flow. Flows
in the Powder River are expected to be about 115 percent of average
with a reasonably likely range of 60 to 171 percent.
End-of-March reservoir storage in Wyoming was 62 percent of
average in Boysen Reservoir and 96 percent of average in Buffalo
Bill Reservoir. Monthend storage was 100 percent of average in
Bighorn Reservoir on the Wyoming/Montana border.
Runoff during March in the Yellowstone River was estimated to be
68 percent of the 1971 to 2000 average at Corwin Springs and 70
percent of that period's average at Billings.
Platte BasinThe high elevation snow pack in the Upper North Platte basin was
103 percent of average on April 1. The snow pack in the North
Platte Basin below Seminoe Reservoir was 96 percent of average.
The snow pack in the South Platte Basin was 106 percent of average.
Precipitation during March in the Platte Basin ranged from below
average to average. March precipitation in the North
Platte Basin above Seminoe Reservoir was 108 percent of average.
In the North Platte Basin between Seminoe Reservoir and Guernsy
Reservoir precipitation was 91 percent of average. The North
Platte Basin below Guernsy Reservoir had 64 percent of average
precipitation. The high elevations of the South Platte Basin had
87 percent of average March precipitation whereas the plains
had 44 percent of average precipitation.
Stream flow in the Platte basin is forecast to range from below
average to above average during the upcoming spring and summer.
Runoff for streams above Seminoe Reservoir are expected to be about
95 to 110 percent of average. Stream flows for the North Platte
below Seminoe Reservoir are forecast to be 65 to 120 percent of
average. The South Platte Basin above South Platte, Colorado can
expect about 110 to 120 percent of average flow. For the remainder
of the South Platte Basin flows are expected to be about 55 to
North Platte Streamflow Fcst South Platte Streamflow Fcst
Stored water in the North Platte Basin as of April 1 was 47 percent
of average. In the South Platte basin stored water was 92 percent of
March 2008 Oct-Mar WY 2008