Portions of northern New Mexico which have been flooding in recent weeks, are listed as “extreme drought” by NOAA.
Flash floods following mountain fires pose increasing threats to drinking water supplies – and add impetus for forest thinning and watershed rehabilitation in the western United States.
The great balls of fire that leapt from treetop to treetop in the Jemez Mountains of northern New Mexico earlier this summer, threatening the town of Los Alamos and a federal nuclear research laboratory, were apocalyptic enough. They left behind a scorched landscape of dead trees, charred woods and blackened earth. From June 26 until early August the Las Conchas burned some 156,000 acres, more than any other single blaze in New Mexico’s history.
Now, however, the threat has turned from fire to floods as the summer “monsoons” deliver high-intensity rains to these burned-out watersheds. Soils laid bare cannot absorb the rainfall and are prone to massive erosion. Recent downpours have produced peak floods through mountain canyons of 20,000 cubic feet per second– thirteen times the average discharge of the Rio Grande – and have carried tree trunks, boulders and tons of blackened soil down to the valley and villages below.
This past week, the utility that provides drinking water to Albuquerque cut its intake from the Rio Grande by half to avoid problems of clogged equipment and the extra cost of treating the sediment-laden river water. To make up for the loss, it pumped more groundwater from shrinking underground reserves.