Posted by Sandra Postel of National Geographic’s Freshwater Initiative in Water Currents on April 29, 2014
When the Las Conchas Fire scorched some 151,000 acres of northern New Mexico in 2011, it wasn’t just the direct fire damage that was cause for worry.
Striking as it did in the midst of a persistent drought, but just before summer “monsoon” rains, the Las Conchas – the largest blaze in New Mexico’s recorded history – set in motion the one-two-three punch of drought, fire and flood that much of the western United States has seen all-too frequently in recent years.
As the intense rains pounded burned-out watersheds, peak floods poured through the Jemez Mountain canyons pushing tree trunks, boulders and tons of blackened soil down to the valleys below. Soon after, to avoid the high costs of de-clogging equipment and treating sediment-laden river water, the Albuquerque drinking water utility cut its intake from the Rio Grande by half – and tapped more groundwater to make up the deficit.
With new research showing that fires in the western United States are getting larger and more frequent, water managers need to mitigate the impacts of fire in their source watersheds, as well as prepare for the consequences.
In a study published online in the journal Geophysical Research Letters, Philip E. Dennison of the University of Utah and colleagues analyzed a database of large wildfires (those greater than 1,000 acres, or 405 hectares) in the western United States over the period 1984-2011 and found a significant increase in the number of large fires and/or the area covered by such fires.
Specifically, in the region stretching from Nebraska to California, the number of large wildfires increased by a rate of seven per year over the 28 years of study, and the total area burned by these fires increased at a rate of nearly 90,000 acres a year – an area the size of Las Vegas.