Blog: Two ways to measure annual rainfall
Over the years, many government agencies have transitioned from the “rainfall year” to a “water year” designation. Hydrologists define a water year as the 12-month period that starts Oct. 1 and continues through Sept. 30 the following year. The state’s water managers and hydrologists tend to like the water year designation because October usually has the least amount of stream and river flows, and it tends to center on the months in which California receives most of its rainfall.