Canadian Forest Service Publications

Theoretical Amounts of Water to Put Out Forest Fires

Year: 2022

Issued by: Pacific Forestry Centre

Catalog ID: 40806

Language: English

Series: Information Report (PFC - Victoria)

Availability: PDF (request by e-mail)

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A system of equations is presented to estimate the mass and depth of water required to extinguish forest fires for three different mechanisms: quenching the flame, cooling the hot fuel in the flaming zone, and wetting the fuel ahead of the flaming zone. A heat balance approach is used to equate the heat required for each mechanism with the amount and heat capacity of water (most of the ‘cooling power’ of water comes from conversion of water to steam). The equations provide a theoretical underpinning for understanding which fire characteristics influence the amounts of water needed, and the relative amounts needed for different fire extinguishing mechanisms. Examples are given for a range of fire intensities which illustrate that water requirements increase at a rate much less than the full power of line fire intensity. Comparing the amount of water applied with the theoretical requirements for a series of low intensity test fires in red pine needles and in slash fuel beds that were extinguished or not extinguished following the application of water confirmed that the theoretical estimates are plausible.