If California farmers continue to overdraft the state's groundwater, the nation's produce basket could dry up in the future.

In a study released July 15, the University of California, Davis, Center for Watershed Sciences presented new data on the state's coastal and southern farm areas. The study also made forecasts of the drought's economic fallout through 2016, according to a news release.

The drought, the third most severe on record, is responsible for the state's greatest water loss ever. In fact, Central Valley river flows have been reduced about one-third.

UC study pegs California ag drought costs at $2.2 billionGroundwater pumping is expected to replace most of the river water. In some areas, pumping is double compared with previous years.

More than 80 percent of this replacement pumping is occurring in the San Joaquin Valley and Tulare Basin.

The results highlight state agriculture's economic resilience as well as its vulnerabilities to a drought. The report underscores the state's reliance on groundwater in times of drought.

If the drought continues for two more years, the reports' authors say groundwater reserves will continue to be used to replace surface water losses. Pumping ability will slowly decrease, while costs and losses will slowly increase due to groundwater depletion.

Failure to replenish groundwater in wet years continues to reduce groundwater availability to sustain agriculture during droughts—a situation lead author Richard Howitt of UC Davis called a "slow-moving train wreck."

California is the only state without statewide groundwater management regulations.

Among the study's findings are:

• Agriculture has incurred $1.5 billion in direct costs—$1 billion in revenue losses and $500 million in additional pumping costs. This is a loss of about 3 percent of the state's total agricultural value.

• The total statewide economic cost of the 2014 drought is $2.2 billion.

• About 5 percent, of 428,000, acres of irrigated cropland have been idled in the Central Valley, Central Coast and Southern California.

• The Central Valley, and particularly the Tulare Basin, is the hardest hit, with projected losses of $810 million.

• Agriculture on the Central Coast and in Southern California will be less affected with about 19,150 acres being idled, $10 million in lost crop revenue and $6.3 million in additional pumping costs.

• Consumer food prices will be largely unaffected. Higher retail prices of high-value California crops, such as nuts, winegrapes and dairy, are driven more by market demand than by the drought.