California water regulators took unprecedented action this week, passing an emergency regulation that will bar thousands of Californians from diverting stream and river water as the drought worsens.

The State Water Resources Control Board voted unanimously Tuesday to pass the “emergency curtailment” order for the Sacramento-San Joaquin Delta watershed. The watershed encompasses a wide swath of the state, from the Oregon border in northeastern California down into the Central Valley.

The regulation — which gives the state water board the authority to issue emergency curtailments and require reporting on water use — will go into effect about two weeks from now, subject to approval by state Office of Administrative Law, with the issuing of formal curtailment orders to follow.

California’s complex water rights system is designed to allocate water use during times of shortage and such curtailments, while rare, are not unheard of. But the scope of Tuesday’s order — which will apply to thousands of senior water rights across a wide swath of the state — goes beyond anything seen in prior droughts.

Read the full story on LATimes.com.