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News Release

Snowpack, Runoff Require Watchful Eye This Spring

Brian Domonkos

April 8, 2014

Across Montana, March snowpack accumulation increased by an average of 13 percent, according to data from the USDA Natural Resources Conservation Service (NRCS). Current statewide snowpack is 143 percent of the median—raising concerns about runoff.

“Increments this month were not as drastic as last month, but snowpack is now requiring more vigilance than usual,” said Brian Domonkos, NRCS water supply specialist for Montana. “Snowpack and streamflow runoff needs to be closely monitored for the remainder of this spring until the majority of mountain snow has run into the rivers of Montana.”

In March, the Wind River basin of Wyoming and the West Fork Bitterroot River were the only two sub-basins that showed declines.The Wind River basin of Wyoming, leading into the Big Horn River, had a two percent decrease and the West Fork Bitterroot River, one percent. All other basins saw improvements, most notably west of the divide, in the Kootenai and the Flathead. 

March precipitation ended the month at 180 percent of average, bringing the year-to-date precipitation to 121 percent of average. “In anticipation of above average spring runoff , many mountain reservoirs are beginning to draw down storage,” Domonkos said. Currently, in most mountain locations, snowpack is slightly above 2011 levels, drawing similarities between April 1, 2011 and 2014 snowpack levels. However, to draw the same similarities between 2011and 2014 runoff would require assumptions of weather conditions.. 

“The 2011 flooding was different from current conditions in a few ways,” Domonkos said. “Besides snowpack accumulating at above normal rates, several significant rain events in 2011 fell on valley snow and caused significant runoff in May. In addition, mountain snowpack in 2011 saw temperatures high enough to melt snow starting in late May and peeking in June, which is later than usual. Right now there are no weather indications that this year will be repeat of the 2011.”  

Snow Water Content
River Basin Percent of Median Last Year Percent of Median
Columbia 141 150
Kootenai, Montana 122 120
Flathead, Montana 138 140
Upper Clark Fork 152 178
Bitterroot 155 184
Lower Clark Fork 136 137
Missouri 145 158
Missouri Headwaters 138 154
- Jefferson 143 163
- Madison 128 146
- Gallatin 137 147
Missouri Mainstem 160 168
- Headwaters Mainstem 171 180
- Smith-Judith-Musselshell 160 167
- Sun-Teton-Marias 149 167
- Milk (Bearpaw Mountains) 161 109
St. Mary 127 128
St. Mary and Milk 131 124
Yellowstone 150 171
Upper Yellowstone 157 174
Lower Yellowstone 143 168
Statewide 143 156

An analysis of 118 SNOTEL sites in Montana watersheds on April 3 showed 30 locations were experiencing the highest snowpack levels of all historical snowpacks, averaging 27 years in the period of record. On April 1, SNOTEL data indicated that statewide snowpack is ranked second of 34 years with 22.2 inches of snow water equivalent (SWE). the only year to exceed this SWE was in 1997 with 26.1 inches. During this time in 2011, snowpack levels were 20.9 inches. Snowpack currently compares most closely to 1982 at 21.7 inches of SWE.

Watersheds at record high (dating back to 1981) snowpacks include: Tongue, Powder, Missouri Mainstem, Upper Yellowstone and the combine Smith-Judith-Musselshell. Five basins that currently maintain snowpacks between the upper 70 and 90 percentiles are: Kootenai, Lower Clark Fork, Madison, Wind and combined St. Mary and Milk River basins.

Streamflow Forecasts

Below are the averaged River Basin streamflow forecasts for the period April 1 through July 31. THESE FORECASTS ASSUME NEAR NORMAL MOISTURE AND RUNOFF CONDITIONS JANUARY THROUGH JULY.

April-July Streamflow Forecast Period
River Basin Forecast as Percent of Normal This Year Forecast as Percent of Last Year Streamflow
Columbia 129 131
Kootenai 107 89
Flathead 123 112
Upper Clark Fork 164 204
Bitterroot 151 198
Lower Clark Fork 139 150
Missouri 146 203
Missouri Headwaters 134 239
- Jefferson 146 327
- Madison 108 149
- Gallatin 129 180
Missouri Mainstem 148 196
Headwaters Mainstem 148 199
Smith-Judith-Musselshell 215 420
Sun-Teton-Marias 136 147
Milk (Bearpaw Mountains) 112 95
St. Mary 112 103
St. Mary and Milk 112 102
Yellowstone 150 199
Upper Yellowstone 139 176
Lower Yellowstone 159 218
Statewide 137 155


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