Sundance, WY – Firefighters and officials are paying close attention to fuel moistures that can affect and change fire behavior.
“Fuel moisture content is generally the most important factor in determining how much of the total fuel is available for burning, and ultimately, how that affects fire behavior” said Jeff Gies, North Zone Fuels Specialist, Black Hills National Forest.
The readings from the amount of moisture in live fuels, such as grass, forbs, shrubs, and pine needles, as well as, several size-classes of dead fuels are used for various management purposes including formulating fire danger levels, determining drought and drying trends, predicting fire behavior, and determining prescription parameters for prescribed burns.
“These readings are an invaluable tool for fire managers when preparing for wildfires and prescribed burns, as well as during fire suppression operations,” said Gies.
Weekly collections, tests and readings are performed by fuels technicians across the Forest.
On the Bearlodge Ranger District, in Sundance, WY, fuels technician, Angela Nordsven, manually measures the moisture contents at two main sites, the “Bearlodge” site located on the northern end and the “Adams” site located on the southern end of the district. To keep readings consistent, they are taken approximately the same time of day and from the same area.
The tests include gathering fuels samples from the various classes of fuels, weighing the samples, drying them in a specially made oven for this purpose, and then weighing the fuel samples again after they have dried. In the dead fuel category, diameter determines if a fuel is a 1-hour (up to ¼” diameter), 10-hour (¼” - 1” diameter), 100-hour, (1” – 3” diameter) or 1,000-hour (3”- 6” diameter) fuel. These time lag categories are loosely defined as the time it takes a diameter class of a dead fuel to reach equilibrium with its local environment. “So smaller fuels respond more quickly to taking moisture in, or drying out,” said Nordsven. “Larger fuels take longer to respond one way or the other.”
“The percent of moisture content held in the live and dead fuels is determined by the difference between the wet and dry sample weights,” said Nordsven. The readings are entered into the National Fuel Moisture Database at: http://www.wfas.net/index.php/national-fuel-moisture-database-moisture-drought-103 “The database keeps track of past year readings, so we can see how this year compares to other years.”
Both the Bearlodge and Adams sites and also a third site at Massengale Flats, part of the U.S. Climate Reference Network operated by NOAA, host remote automated weather stations (RAWS). The RAWS feed information to the Great Plains Dispatch Center, (GPC) located outside of Rapid City, SD. Fire managers are able to instantly access data from the RAWS to obtain information on temperature, fuel moistures, precipitation, relative humidity, burning index, wind speed and direction.
“There are several other RAWS sites across the Black Hills area that are maintained by the Forest Service as well as other agencies,” said Gies.
“The manual and RAWS station readings provide important information that is used for tracking trends, supporting other fire and weather management systems, and providing real-time data that can be crucial for predicting fire behavior during wildfires and prescribed fires,” Gies said.
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