How much does wildfire reduce forest water use and increase runoff?
Wildfire is reshaping the forests of California’s Sierra Nevada and affecting the water those forests supply to downstream users. A paper published in Hydrology and Earth System Science reports that the effect of wildfire on potential runoff from the state’s main water-supply watersheds has increased in the period 1985-2023, most markedly since 2019. To measure how much water forests use, researchers from UC Merced, UC Berkeley and UC Irvine used data on evapotranspiration, the measure of water evaporating from soil and released by plants. … The researchers found that by 2023, the cumulative burned area,about one-fifth of the total watershed, resulted in a potential runoff increase of about 740,000 acre-feet per year, or about 5.4 percent of the combined average full-natural flow from these basins.
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