California water regulators accepted an offer from some growers in the Sacramento-San Joaquin River Delta to cut water use by 25% or fallow equivalent acreage. But the deal has limited relevance to regions operating with little or no state water during the drought.

The concessions by senior water rights holders come as the state is warning such rights — more than a century old — may be curtailed, and soon after Gov. Jerry Brown moved to cut urban water use by 25%.

The pact with the State Water Resources Control Board in the Delta, which represents less than 10% of California’s farmland, applies to participating landowners with direct access to a river or stream. They must apply online by June 1 and observe the restrictions through September.

Brown’s drought emergency measure prompted some urban calls for more conservation or cuts in agriculture. But for growers outside the Delta, or those who lack senior rights, it’s not always clear what more can be done.

“It’s interesting that a region has taken a voluntary measure to cut their use by 25%, but much of the industry has already faced mandatory cuts that far exceed that,” said Mike Wade, executive director at the California Farm Water Coalition. “About 60% of the state’s irrigated farmland has already faced a mandatory cut on average of 70%. And 44% of the state’s irrigated crop is getting a zero allocation. You can’t cut any more than that.”

The coalition surveyed 5.8 million acres and their expected surface water allocation for the year. Growers in the San Joaquin Valley and elsewhere already rely heavily on groundwater.

“California has a really diverse water system,” said Dave Kranz, communications manager for the California Farm Bureau Federation. “So solutions that work in one region or watershed may not work elsewhere. The Delta watershed is a very specific geographic and hydrological situation.”

“Farmers in many parts of California have participated in a variety of cooperative efforts,” Kranz said. “People will remain cooperative in the short term but stay focused on long-term efforts to improve overall supplies. The real answer is to have a more flexible water system through improved storage and other efforts to try to avoid being in this situation in future drought years.”