ARIZONA — A test project conducted in the Kaibab National Forest has found that thinning 3,400 acres of ponderosa forest saves about 260 acre-feet of water per year, or about 75 million gallons. One acre-foot of water provides enough to support one household for a year. Thinning 1 million acres could save 90,000 acre-feet of water. And that’s worth about $50 million, according to the U.S. Bureau of Reclamation. The test project researchers created a high-resolution map of the watershed using light detection and ranging imagery. This helped researchers at ASU’s Center for Hydrologic Innovations create a three-dimensional map of the watershed and estimate the extra water produced. The reduction in trees and brush allowed more water to flow into streams. …The Forest Service has been struggling for a decade to thin forests through the 4-Forests Restoration Initiative, but the need to get rid of low-value biomass has stalled large-scale thinning efforts.