Method. Volumes are accumulated from October 1 of the current water year through the most recent complete day, and compared against the median accumulation over the same calendar window in prior water years — not against complete-year totals. This keeps the comparison like-for-like partway through a water year; a partial year measured against full years would understate flow at every station.

What is an acre-foot? One acre-foot (AF) is the amount of water it takes to cover one acre, about the size of a football field, one foot deep — roughly 326,000 gallons. In Colorado, one acre-foot typically supplies the annual water needs of about two to four households, so 1,000 acre-feet (1 KAF) is enough for roughly 2,000 to 4,000 households for a year. For comparison, alfalfa — one of the most water-intensive crops grown in this region — typically uses 2.5 to 3 acre-feet per acre per year in southwestern Colorado, so 1 KAF is also roughly enough to irrigate 300 to 400 acres of alfalfa for a full season.