SACRAMENTO (AP) — A majority of farmers and others holding some of California’s strongest claims to water have missed a deadline to confirm they stopped pumping from rivers and streams, state officials said Monday.

Data show less than a third of the farmers, water districts and communities responded to the broadest conservation order for those with nearly ironclad water rights by the State Water Resources Control Board.

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The board’s order earlier this month affected 277 century-old rights to water from the Sacramento, San Joaquin and delta watersheds in the agriculture-rich Central Valley. State officials expect to demand even more of these senior water rights holders to stop diverting water as rivers and streams run too dry to meet demand in California’s fourth year of drought.

The dry spell has prompted deep cuts to deliveries from government reservoirs and to farmers with more recent, and less secure, claims to water. Cities and towns serving residents and businesses are also under order to cut water use as much as 36 percent compared to 2013 levels.

Senior water rights-holders are historically spared from cuts, and some are challenging state cuts in court to keep it that way so farmers they serve can keep watering crops and taking care of livestock.

Water rights-enforcement manager Kathy Mrowka said she is reviewing the response data and didn’t have an immediate explanation for why it lagged.

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The senior water rights-holders who didn’t respond to the water board within seven days were expected to take about 200,000 acre feet of water over the summer, a small sliver of the state’s total water use.

She previously said entities that ignore the water board would be the first to face inspections and enforcement. The punishment for taking water is $1,000 a day and $2,500 per acre foot, enough water to fill an acre of land 1 foot deep.

Some people who have not responded to the board may not be illegally taking water because the streams and creeks to which they hold rights have dried out. Others may not have missed the state’s curtailment notices or are waiting for a court decision in the coming days before responding.

Those ordered to stop diverting from waterways have other options, including tapping groundwater, buying water at rising costs, using previously stored water or leaving fields unplanted.

Regulators have ordered thousands of other entities with less secure claims known as junior water rights to stop pumping. Only about a third of them have confirmed they stopped diverting water, although the ones that did respond are among the biggest water users.

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