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California Water Science Center

California Drought

In 119 years of recorded history, 2013 was the driest calendar year for the state of California. On January 17, 2014 California State Governor, Jerry Brown, declared a drought state of emergency.

Snowpack, through runoff, provides about one-third of the water used by California's cities and farms. On May 1, 2014, the Department of Water Resources released their final Snow Survey of the year results stating that the statewide snowpack's water content is at 18% of average for the date. As of December 8, 2014, the California Department of Water Resources measured the statewide water content of snowpack at only 7% of the average historical April 1 snowpack measurement - crucial because this is when the snowpack is normally at its peak and begins to melt into streams and reservoirs.

Closely monitoring the effects of, and studying the current drought in the context of long-term hydrologic, climatic, and environmental changes, is essential for successful science-based planning and preparedness for future droughts.

Drought Defined

A drought is a period of drier-than-normal conditions that results in water-related problems. When rainfall is less than normal for several weeks, months, or years, the flow of streams and rivers declines, water levels in lakes and reservoirs fall, and the depth to water in wells increases. If dry weather persists and water-supply problems develop, the dry period can become a drought.

The term "drought" can have different meanings to different people, depending on how a water deficiency affects them. Droughts have been classified into different types such as:

  • meteorological drought - lack of precipitation
  • agricultural drought - lack of soil moisture, or
  • hydrologic drought -reduced streamflow or groundwater levels

It is not unusual for a given period of water deficiency to represent a more severe drought of one type than another type. For example, a prolonged dry period during the summer may substantially lower the yield of crops due to a shortage of soil moisture in the plant root zone but have little effect on groundwater storage replenished the previous spring.

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What are the effects of drought?

Water quality degradation, surface and groundwater level declines, land subsidence - all are impacts of drought. Understanding the impacts of drought can help mitigate drought-related issues and prepare for future dry periods.

small graphic of a streamflow datamap

How does drought affect groundwater?

Groundwater provides drinking water for a large portion of the nation's population, supplies business and industries, and is used extensively for irrigation. But what happens to this resource during drought?

small graphic of a streamflow datamap

How does drought affect surface water?

Careful observation and analysis of the movement and condition of surface water is essential for understanding this resource, especially during times of drought. The California Water Science Center uses a network of over 400 streamgages to collect real-time data on surface water at locations across the state.

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How is water managed during a drought?

Water shortages during drought are not only a concern for humans, but for ecosystems in the Bay Delta and Central Valley as well.