Dirt roads neatly bisect acres and acres of vibrant green plants here: short, dense alfalfa plants fed by the waters of the Colorado River, flowing by as a light brown stream through miles of narrow concrete ditches. But on a nearby field, farmer Ronnie Leimgruber is abandoning those ditches, part of a system that has served farmers well for decades. Instead, he’s overseeing the installation of new irrigation technology, at a cost of more than $400,000, and with no guarantee it will be as dependable as the open concrete channels and gravity-fed systems that have long watered these lands. … What Leimgruber is pursuing on his acreage is part business savvy and part guarding against a drier future. Like many farmers in this region, he’s figuring out how to keep growing his crops with less water. Two decades of drought have shrunk the Colorado River, which feeds farms in the Imperial Valley, an agricultural oasis fed solely by the 82-mile All-American Canal, which delivers river water to this arid Southern California region.