Los Altos Weather – A September Storm, California’s Drought to Continue

This post continues a monthly series of posts about California’s drought, with weather data from my hometown of Los Altos, south of San Francisco.

We had a September rainstorm of .41 inches, more than the total rainfall (.25 inch) we normally get for the four months of June to September. Our dry season is almost over, but California’s drought is now forecast to continue through the end of 2014. Local groundwater levels fell significantly during the past year, so we’re pumping more groundwater than is being replenished. California passed a historic law saying that we’ll manage groundwater by 2040. Almost all the oil wells fracked in California draw their water from the California aqueduct, based on early reports.

Here’s the Los Altos rainfall for 2013 and 2014. Since May our monthly rainfall has been less than half an inch.

September Storm, but Little Rain
September Storm, but Little Rain

The lack of rain the past few months is dwarfed by the low rainfall for three years. The chart below shows our accumulated low rainfall for 2013 and 2014.

Low rainfall for 2013 and 2014
Low rainfall for 2013 and 2014

The trend of above-normal monthly low temperatures continues.

Monthly low temperatures above normal
Monthly low temperatures above normal

This spring and summer, the US Weather Service predicted an El Niño event, which indicates above-normal rainfall. However, as shown in the above featured image, they now predict below-normal rain for most of California through the end of the year, so our drought is expected to continue. OND is the Weather Service’s abbreviation for October-November-December, and CPC is the Climate Prediction Center. From their September drought update,

For the OND season, CPC’s precipitation outlook favors below-median precipitation over northern California and northwestern Nevada, above-median precipitation over far southern California, and EC anticipated elsewhere. The U.S. Seasonal Drought Outlook favors drought persistence/intensification across all but far southern sections of both California and Nevada, and much of western Utah.

With less rainfall, California has reduced deliveries of water to farmers and cities. To compensate for reduced deliveries from the State, our local water companies might be pumping more groundwater.

The California Department of Water Resources shows that groundwater levels in the south San Francisco Bay Area have fallen during the past year. All wells show decreased groundwater level, as shown by the yellow, orange, and red dots. As shown by the red dots, the groundwater level at about half the wells has fallen by more than ten feet. The falling groundwater level indicates that we’re pumping groundwater faster than it’s being replenished. This data is from Spring 2014. With reduced water deliveries this summer, overdrafts of groundwater will probably continue.

Bay Area groundwater levels falling
Bay Area groundwater levels falling

As the groundwater level drops, the risk of subsidence, our ground sinking, increases. The town of Alviso dropped thirteen feet due to subsidence in the early 1900s. Many communities ring the south bay and are therefore vulnerable to increased flooding if our ground sinks due to groundwater pumping. The thirteen feet of subsidence last century is several times more than any EPA estimate of sea level rise during this century.

“California will no longer be the only western state with a pump-as-you-please approach to groundwater” is the lead paragraph for this Wall Street Journal article. From National Geographic, in September “California Governor Jerry Brown signed a package of three bills designed to regulate the pumping of water from underground aquifers.” This is important for California because “aquifers provide 30 to 40 percent of the state’s water supply in normal years but close to 60 percent in drought years.” “The new laws give local agencies five to seven years to develop those groundwater plans, and until 2040 to implement them.” The new laws are a step in the right direction, but the new laws allow 25 years for plans to be drafted and implemented.

Water is sometimes used to extract oil — fracking uses high-pressure blend of water, sand and chemicals to crack rocks containing oil or natural gas. A federal study found that “fracking for oil in California happens at shallower depths than previously realized and could pose a risk to precious groundwater supplies”, especially in Kern County. Per well reports to date, 93% of fracked California wells used water from the California aqueduct; 6% used groundwater.


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I enjoy travel, art, food, photography, nature, California native plants, history, and yoga. I am a retired software engineer. The gravatar is a Nuttall's woodpecker that visited our backyard.

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