NASA images released this week show the severity of drought-stricken California's declining water storage over the past decade.
The images from the space agency's Gravity Recovery and Climate Experiment satellites (GRACE) show the state's accumulated water loss from June 2002 to June 2008 and June 2014. The progression of colors from green to red indicate declining water storage in a state that faces a fourth-consecutive dry year.
The GRACE satellite images depict changes in mass related to changes in water amount on or below the Earth's surface. Those changes are represented by different colors in satellite imagery.
The most severe storage losses -- depicted by the most severe color changes in the images -- between 2002 and 2014 occurred in the Sacramento and San Joaquin River basins, including the Central Valley, because of increased groundwater pumping to support agricultural production, according to NASA. The images show a large swath of the central part of the state changing from green to orange to a blistering red, representing a severe reduction in mass due to declining water storage.
The river basins lost a combined 4 trillion gallons of water annually between 2011 and 2014, according to NASA. Californians draw about 38 billion gallons per day from ground and surface-water sources, according to a USGS survey.
Earlier this year, Gov. Jerry Brown declared a drought emergency in California, where state and local water agencies are urging resident to conserve and even considering plans to budget water use by creating a daily water allocation for each household.
More than 58 percent of the state is under "exceptional" drought conditions, according to the U.S. Drought Monitor. Three months ago, about 36 percent of the state was in the "exceptional" category, the most severe of the agency's drought levels.
More than 95 percent of California is under severe to exceptional drought.