Update from the Pacific Institute California Drought Response Group – May 9


For the latest updates about the California drought go to www.californiadrought.org

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This week in… Weather Forecasting

Federal weather forecasters at the National Oceanic and Atmospheric Administration have increased the probability that an El Niño weather system will develop this winter to 78%, up from 66% last month. According to the International Research Institute for Climate and Society at Columbia University, El Niño events tend to develop between April and June, and reach maximum strength between December and February.


This figure shows the probability of El Niño and La Niña events, as well as neutral conditions, for 3-month intervals between April 2014 and February 2015. The forecast is based on a consensus of CPC and IRI forecasters, in association with the official CPC/IRI ENSO Diagnostic Discussion.
Source: Columbia University

Although these events tend to produce more rainfall in California, development of an El Niño would not guarantee an end to drought conditions. While they tend to produce wetter conditions in southern California, precipitation in central and northern California is more unpredictable. “I don’t want to recommend that you invest any of your retirement in the umbrella market yet,” said Bill Patzert, a research scientist and oceanographer at NASA’s Jet Propulsion Laboratory in Pasadena.

In addition, El Niño events are characterized by sea surface temperatures that are warmer than average. Couple this with warming that is already occurring as a result of increased greenhouse gasses in the atmosphere, and an El Niño event could result in significantly higher global temperatures. The 1998 and 2005 El Niño years were the warmest on record. Higher temperatures would result in more precipitation in the form of rain rather than snow, increasing the risk of flooding, landslides, and coastal erosion, and reducing the amount of water storage in snowpack.

In Other News:

  • On May 5th, the California Water Foundation released a framework for sustainable groundwater management. The report was put together with input from water agencies and associations, natural resource conservation advocates, environmental justice advocates, county representatives, representatives from the agriculture industry, farm bureaus, water quality advocates, and legislative and administrative officials.
  • The U.S. National Climate Assessment Report was released on Tuesday and the report’s findings aren’t pretty (although the website certainly is).
  • The Kern County Water Agency is putting together a plan to reverse the flow of the California Aqueduct, bringing up to 8 million gallons per day from the Kern Water Bank to parched farmers along a 47 mile stretch of the Central Valley.

California Drought Status

US Drought Monitor

There has been effectively no change in statewide drought conditions from last week.


Except for a patch of rain in Fresno County and minimal precipitation in the north, most of central and southern California received little to no rain this past week.

This graph from the California Department of Water Resources shows the percent of average precipitation for the water year for cities throughout California. South Lake Tahoe has had the highest percent of normal precipitation at 68%, with average precipitation in Palm Springs a mere 19% of normal. The color indicates regional river conditions; visit DWR’s website for more detailed information on river levels and flows.




California snowpack is currently at about 9% of the April 1st average, down from 13% last week. The final snow survey of the year was released on May 1st, which found the snowpack water content at about 18% of the May 1st average.

Water Supply Conditions

This graph shows statewide percent of average conditions on April 1st for 2001 through 2014. The graph includes averages for snowpack, precipitation, runoff, and reservoir storage. May has yet to be updated, but we’ll post it when it is.

Reservoir Conditions

Reservoir conditions haven’t changed much at all since last week.