Climate intelligence for the great outdoors.

## National Hydrology and Climate Brief: May 19, 2026

California's reservoir crisis has reached a critical juncture, with multiple storage facilities showing dramatic swings that underscore the state's volatile water situation. While several reservoirs are experiencing exceptional abundance—Prado Dam at 417% of normal, Thomas A Edison at 226%, Florence Lake at 233%, and Lake San Antonio at 204%—two major water sources present alarming deficits. Hetch Hetchy Reservoir, a cornerstone of San Francisco's water supply, sits virtually empty alongside Donnells Reservoir, both showing catastrophic storage losses. This stark disparity reflects California's ongoing struggle with extreme precipitation variability, compounded by wildfire threats now forcing evacuations near Los Angeles as the Sandy Fire and a second blaze challenge containment efforts, triggering smoke advisories across multiple Southern California communities.

The nation's major river systems are running at remarkable volumes, with the Ohio River at Old Shawneetown cresting at 259,000 cubic feet per second—among the highest flows recorded this spring. The Mississippi River system shows sustained elevated flows from Minnesota through the Lower Mississippi Valley, while the Sacramento River maintains robust discharge at 15,900 cfs. These conditions create favorable circumstances for commercial navigation but pose ongoing flood risks in low-lying areas. Meanwhile, **critical infrastructure failures are evident across multiple states**: monitoring stations in North Dakota, Texas, Maryland, and Washington have gone offline, with New Mexico's Jemez Canyon Reservoir showing zero storage against a 15,913 acre-foot average. Houston faces another round of heavy rainfall Wednesday with flood advisories in effect, while minimal snowfall (2 inches maximum) in Washington and Colorado signals the final gasps of the 2025-26 snow season, with Alaska's North Slope expecting the only significant accumulation in coming days.