John Austin of Three Rivers visited the Tulare County Water Commission last week to relay his new presentation about droughts and water availability in California.
The latest research shows less water in Sierra rivers than previous dry and wet years and higher average temperatures, he said.
The double whammy of higher temperatures and drought has helped cause massive tree mortality. At least 66 million conifers in California have died since 2010 because of water stress, he said.
For trees and plants, “it is probably the worst 16-year period in more than 850 years, since about the 1150s,” he said.
Since the mid-1980s, “droughts have become more severe” in California and the western U.S., he said. “How come this is? What’s going on?”
Austin is a retired National Park Service employee.
One of his jobs was to determine how high to build a bridge over the south fork of the Kings River so floods wouldn’t wipe it out. He studied the history of flooding on the south fork to get the answer and expanded his inquiry to all rivers of the South Valley.
Austin notes that he is not a researcher himself but compiles recent scientific discoveries by others. Lately, he’s been analyzing studies about droughts in California in the past three decades.
“We seem to have entered a new normal,” Austin said.
Since the mid-1980s, there has been a decrease in runoff from Sierra rivers compared to the previous nine decades, he said.
The decrease has been greatest in the Tule and Kern river basins, with up to 20 percent less runoff.
There has been a decrease of about 13 percent to 15 percent in Kaweah, Kings and upper San Joaquin river basins.
The four biggest river basins in the Sacramento Valley have experienced an average decrease of about 11 percent.
Why the decreased runoff? There are three plausible explanations, he said.
One theory is that there have been fewer storms, and studies show the number of storms hitting the state has been falling.
“There has been 7 percent per decade decrease in the number of storms for the last three decades,” Austin said, citing research by Andreas Prein of the National Center for Atmospheric Research.
The reason for the decrease in storms is the high pressure ridge often parked over the western United States. “It has become more persistent and pronounced,” Austin said, citing research led by Stanford University scientist Daniel Swain.
Another theory is that higher temperatures are causing plants to consume more water to stay alive, leaving less for rivers.
Since 1895, the average annual temperature in California has been increasing – and rising dramatically since the mid-1980s, according to research by climate professor Park Williams at Columbia University and others.
A third theory is that dry and wet years of the past 30 years are no more than a statistical anomaly.
“We had nine wet years from 1978 to 1986,” Austin said. “Maybe the wet years are about to return. Maybe we are not being patient.”
But with 30 years of data, “it looks like a trend,” he said.
Austin gives presentations to community groups about floods, drought and water availability. He can be reached at firstname.lastname@example.org.