A handful of landowners—about 500 farms in all—control the rights to 3.1 million acre-feet a year from the Colorado River. That’s equal to about a third of the water used by California’s cities, with 37 million people, where a four-year drought means neighbors report you if your lawn is green. Or, to measure another way, it’s half again as much water as Governor Jerry Brown aims to save under his April executive order, which set a February 2016 deadline for a 25 percent reduction in urban use. An acre-foot is about 326,000 gallons (1.2 million liters) and can supply the household needs of about 10 people for a year, though actual water use rates vary widely. ... Imperial Valley farmers know their water is precious and understand that to preserve a way of life that runs back a century they have to grapple with the needs of a drought-stricken state. Politicians, regulators, and lawyers have squeezed the valley before to get at its water. In 2003, the Imperial Irrigation District, under pressure from Senator Dianne Feinstein and other federal and state officials, controversially agreed to sell as much as 280,000 acre-feet a year to San Diego. Farmers here still discuss that episode at length, and emotions are still raw, because they believe similar water transfers are likely in the valley’s future. ... “People think transferring water out of the valley is a great sin,” he says. “Wasting water can be an even greater sin.” The neatly prepared field he’s inspecting is perfectly level—he uses lasers to make sure—and slightly lower than adjacent sections so water moves by gravity at an optimal speed. ... The most basic principle governing water use in the western U.S. is this: first in time, first in right. That’s why Imperial Valley farmers have so much water. They arrived early, building the first canal to withdraw Colorado River water and ship it to the valley in 1901. ... More than half the people who own land in the valley today live elsewhere.