California's 19th-century water laws give nearly 4,000 companies, farms and others an unmonitored amount of free water, while the state is mired in a three-year drought that has forced water cutbacks to cities and agriculture.

An Associated Press review of state Water Resources Control Board records found:

— This group holds more than half of the claims on the state's waterways and uses trillions of gallons of water each year.

— The water rights system relies on self-reported water use records full of errors and years out of date, meaning officials do not know if rights holders are over-drawing or wasting water.

— More than half of the entities with pre-1914 water rights are corporations, and also among the biggest holders are the water departments of San Francisco and Los Angeles.

— Companies, farmers and cities with such water rights are exempt from drought-related cuts in water allotments this year, although they collectively are the biggest water consumers.

— This anachronistic system blunts California water managers' ability to move water where it's most needed.