Snow won't end California's Thirst: UC Water researchers in news
Sierra Nevada snow won't end California's Thrist
This article was originally published in The New York Times after Prof. Roger Bales and colleagues showed the reporter the state of the snow on 4/7/16. The article has been excerpted to feature UC Water researchers. Full article available online.
Many of those concerns [about snow] stem from the effects fo climate change and the structure of Sierra forests, which can influence how the snowpack accumulates and melts. Because the snow, in effect, serves as a reservoir that is released over time, any changes can affect how much water is available for people, industry and agriculture, and when.
"We'll be getting mroe rain and less snow here," said Roger Bales, a professor at the University of California, Merced, and a principal investigator with the Southern Sierra Critical Zone Observatory, which studies snowpack and other water-related issues. "That means less snowpack storage and faster runoff."
Dr. Bales was standing on a snow slope in Yosemite last Thursday, at about 7,000 feet elevation, just off a 19th-century wagon road that is used by hikers and snowshoers. Nearby, amid car-size granite boulders and close to a soaring Ponderosa pine, were instruments that he and his fellow researcher use to obtain detailed information about the snowpack in several spots throughout the southern Sierra.
The effects of warmer temperatures can already be seen here, Dr. Bales said.
"Historically, this has been the reliable snow zone, where it accumulates till late March or early April and then melts," he said. But now the snowpack here is more like that at lower elevations, "where it will accumulate, melt, accumulate, melt," he said.
Less snow, earlier melting and faster growth mean that more trees are running out of water in the summer. Mohammad Safeeq, a colleague of Dr. Bales at the university, said that, in general, water was flowing off the mountains two weeks earlier than in the past. "Two weeks in a three-month summer window is significant," he said.
Water-stressed trees are more susceptible to pests and disease, so one result of the changes is more tree deaths. This is readily apparent at Yosemite in the drive from the valley floor, where the green hillsides are dotted -- in some cases in large numbers -- with the brown of dead pines and firs.
Contributing to the problem is the fact that there are many more trees here than there used to be. A century ago, Dr. Safeeq said, Yosemite had perhaps 80 trees an acre; now the number is closer to 250.
But smaller, less instens fires are nature's way of thinning the forest, culling trees that are less fire-resistant, said Martha H. Conklin, a UC Merced professor and another principal investigator with the observatory. Paradoxically, because fire suppression leaves so much timber on the moutnains, it can lead to much bigger and hotter fires, like the Rim Fire that burned 250,000 acres in and around Yosemite and destroyed more than 100 structures.
If small fires were allowed to burn, Dr. Conklin said, "you'd have a forest of a very different structure." Even the types of trees would eventually change, she said, as species that are better able to resist fire replaced others. "I don't know if we can ever go back to a forest that has a natural fire regime," Dr. Conklin said. "It's very difficult to let a fire burn if you have houses dispersed in the forest."
But with climate change affecting how much water is available from the mountains, she added, "we have to think about how we're going to manage these forests."
A version of this article appears in print on April 12, 2016, on page D1 of the New York edition with the headline: Uncertainty in the Sierra. Read the full article online.