Through the marshlands along the Oregon-California border, the federal government a century ago carved a whole new landscape, draining lakes and channeling rivers to build a farming economy that now supplies alfalfa for dairy cows and potatoes for Frito-Lay chips.

The drawdowns needed to cover the croplands and the impacts on local fish nearing extinction have long been a point of conflict at the Klamath Project, but this year’s historic drought has heightened the stakes, with salmon dying en masse and Oregon’s largest lake draining below critical thresholds for managing fish survival. Hoping to limit the carnage, federal officials have shut the gates that feed the project’s sprawling irrigation system, telling farmers the water that has flowed every year since 1907 will not be available.

Some farmers, furious about water rights and fearing financial ruin, are already organizing a resistance. “Tell Pharaoh let our water feed the Earth,” said a sign erected near the nearly dry irrigation canal that would usually be flowing with water from Upper Klamath Lake in southern Oregon.

The brewing battle over the century-old Klamath Project is an early window into the water shortfalls that are likely to spread across the West as a widespread drought, associated with a warming climate, parches watersheds throughout the region.

In Nevada, water levels have dropped so drastically in Lake Mead that officials are preparing for a serious shortage that could prompt major reductions in Colorado River water deliveries next year. In California, Gov. Gavin Newsom has placed 41 counties under a state of emergency.

While drought consumed much of the West last year, setting the stage for an extensive wildfire season, the conditions this spring are far worse than a year ago. More than half of the West faces “extreme” drought conditions, according to the U.S. Drought Monitor, including wide areas of California and Oregon. Scientists have said the region may be going through the worst drought period in centuries.

Here in Oregon, conservationists, Native American tribes, government agencies and irrigators are squaring off, and local leaders fear that generations of tensions could escalate in volatile new ways.

“There are folks on both sides that would really like to throw down and take things in an ugly direction,” said Clayton Dumont, a member of the Klamath Tribal Council. “I hope it doesn’t happen, but it’s a possibility.”

“Who cares if there is violence? At least something will be worked out,” Mr. Bundy said in an interview, ridiculing those not prepared to fight for the nation’s food supply. “‘Oh, we don’t want violence, we’ll just starve to death.’ Heaven forbid we talk about violence.”

The region has a deep history rooted in violence and racial division. In 1846, U.S. War Department surveyors, led by John C. Frémont and Kit Carson, slaughtered more than a dozen Native Americans on the shores of Klamath Lake. The Klamath Tribes eventually signed a treaty surrendering some 20 million acres of their historic lands in exchange for a reservation along Upper Klamath Lake and the perpetual right to hunt and fish.