Topsoil Decline In California, Extreme Drought Expands In Western U.S.

The U.S. Drought Monitor report released August 27 noted that topsoil moisture in California declined last week and extreme drought expanded in Oregon and Washington.

"No revisions were considered necessary this week in either the Southwest or California," according to the U.S. Drought Monitor.  

In California, 92 percent of the state is in severe drought, 71 percent is in extreme and 46 percent is in exceptional drought. The Drought Monitor drought intensity levels are Abnormally Dry, Moderate, Severe, Extreme and Exceptional Drought.

In Nevada, 76 percent is in severe drought, 38 percent is in extreme and 16 percent is in exceptional drought.

This week’s report referred to recent reports that land in central California’s agricultural region "is sinking quickly because of the state's historic drought."

"This is forcing farmers to spend millions of dollars upgrading irrigation canals, and putting roads, bridges, and other infrastructure at risk," says the Drought Monitor report. "The extent of Short to very Short topsoil moisture for the state of California as a whole, is generally around 80 percent, a decline of about 5 percent since last week."

While there were no changes in the percentage of drought in California or Nevada, "Extreme drought (D3) coverage was expanded across east-central Washington, and north-central and northeastern Oregon."

Oregon and Washington remain 100 percent in severe drought but the weekly changes in the percentage of extreme drought were dramatic.

In Oregon, extreme drought increased from about 50 percent to 67.29 percent week over week.

In Washington, where recent large wildfires have burned more than 800,000 acres, the percentage of extreme drought increased nearly 35 percent from the previous week, from 50.80 percent to 84.64 percent.

"Some considerations in the D3 expansion [extreme drought] across the Northwest include daily record low stream flows, short-term (2-month) Standardized Precipitation Index (SPI) values, and low precipitation amounts from June 1 – present time throughout the region. In some cases, record or near-record dryness was reported for the June 1 – present time," the report stated.

The long-term drought outook from the National Weather Service Climate Prediction Center shows the drought persisting and intensifying through November 2015  in most of California, Nevada and Idaho, and in all of Oregon and Washington.