Those conflicting factors came into play last week when the state Water Resources Control Board voted unanimously to curtail nearly all agricultural water diversions from the Sacramento-San Joaquin Delta watershed, which stretches about 500 miles from near the Oregon border to near the Tehachapi Mountains.

The decree will affect farmers, who use most of the water allocated for human use, but not immediately. The season for irrigating crops is nearly over and water managers delivered a fairly substantial share of agricultural water earlier in the year — too much in the eyes of environmental groups.

However, if drought and the board’s no-diversion policy continue into 2022, they will almost certainly ignite a high-stakes political and legal conflict over whether the state can essentially usurp historic water rights and dictate how local farm water systems are to be operated.

Valerie Kincaid, a water law attorney who represents the San Joaquin Tributaries Authority, bluntly told the board, “We now have a draft regulation that exceeds water board authority,” hinting that a legal battle over water rights is looming.

Status of Pre-1914 Water Rights Being Questioned

The state first began regulating water in 1914 and holders of pre-existing water rights, plus landowners adjacent to waterways, have long been presumed to have virtually unfettered rights to draw water without regulation.

However, in more recent years, the legal status of those pre-1914 rights has been questioned. As drought gripped the state during his first stint as governor 40-plus years ago, Jerry Brown appointed a commission to review water rights, saying, “the existing law included impediments to the fullest beneficial use of California’s water.”

Nothing came of that effort but when another drought hit during Brown’s second governorship, his water board appointees attempted to breach senior water rights by punishing a small water district near Tracy for ignoring a curtailment order.

“We are a test case,” the Byron-Bethany district’s manager, Rick Gilmore, said at the time. “I think this has become a larger issue. I think the water board wants to use this as a precedent so they can start to gain more control over senior water right users.”

Water Rights Battle

The conflict fizzled before it could morph into an all-out legal battle but other senior rights holders did win a legal ruling that the state was issuing its curtailment decrees without due process.

Environmental groups and some agricultural interests that lack water rights, such as the immense Westlands Water District, seem to be spoiling for a water rights battle.

Westlands endorsed last week’s board action, referring to deliveries to senior rights holders as “unlawful diversions” of water needed to maintain water quality. Westlands thus became a strange bedfellows ally of the Natural Resources Defense Council, which complains that the federal Central Valley Project gave farmers with senior rights too much Lake Shasta water in the spring, leaving too little to support salmon spawning runs.