A sharp, sudden and unexpected drop in rivers and tributaries will cause unprecedented state-ordered shutoffs in June and July to hundreds of irrigators in Western and Eastern Washington.

The Washington Department of Ecology says it has a legal obligation to cut off farmers with junior water rights to preserve minimum flows for fish and irrigators with senior rights.

Some of the irrigators have lost their water before, but not until late in the growing season. Rivers have fallen to levels typical of August or September, ecology officials say.

“It’s just been a real dramatic drop in the last week,” DOE spokeswoman Joye Redfield-Wilder said. “It’s just so widespread and indicative of a new day out there.”

Beginning Monday, about 260 irrigators on the Methow, Colville and Little Spokane rivers will have their water shut off. They can call a DOE phone number daily to check whether the restriction has been lifted, but the answer will be no for the rest of the summer unless there’s enough rain to cause rivers to spike, Redfield-Wilder said.

Another 80 irrigators in the Okanogan and Similkameen watersheds in north-central Washington were cut off June 23, while more than 40 irrigators on the Wenatchee River lost water June 15.

In Western Washington, DOE plans to deliver shutoff notices by mid-July to about 70 irrigators in the Chehalis River Basin, an agricultural area in Southwest Washington. Those irrigators were last shut off in 2006, but not until September.

Officials in the spring said Washington was experiencing a “snowpack drought.” Record-breaking heat and an almost complete absence of rain this month have made that description incomplete.

South-central Washington farmer Neal Brown said Friday that a week ago he still hoped his spring wheat would yield an averaged-sized crop. Amid a triple-digit wave and month-long dry spell in Klickitat County, he’s slashed his expectations in half.

“It’s really quite remarkable,” he said “It’s degrading rapidly.”

The Chehalis River relies on rain, not snow. DOE’s water resource manager for Southwest Washington, Mike Gallagher, said that two weeks ago he wouldn’t have predicted the basin’s irrigators would be shut off.

“There’s been a remarkable drop in the last two or three weeks,” he said. “This is unchartered territory for all of us.”

Gallagher said water could be restored if there’s enough rain. But he said the chances aren’t good for relief this summer. “We need a wet and snowy winter,” he said.

So far, only the Chehalis Basin has been targeted for shut off notices on the westside. But other Western Washington rivers are being monitored. “All across Western Washington, we’re seeing flows typical of August and September, not June,” DOE spokesman Chase Gallagher said.

For much of the spring, about one-fifth of the state’s rivers and streams were recording record low flows, according to the U.S. Geological Survey. The percentage topped 30 percent June 11 and has stayed there since.

Some 39 percent were at record low flows June 26. On the same date in 2005, the last statewide drought, 10 percent were at record lows.