October 1st marks the beginning of the water year. What is the water year? Here’s an answer from the CoCoRaHS web site at https://www.cocorahs.org/Content.aspx?page=mod&mod=1:
“The water year is the best consecutive twelve months that span the “water storage/water usage” hydrologic cycle. The water year cycle is particularly obvious in the Rocky Mountains and western U.S. where snow begins to accumulate at high elevations in October and doesn’t melt and run off until next spring and summer. But this same important annual cycle takes different forms across the entire country.”
A number of online climate products use information accumulated from October 1 as a way of keeping track of accumulated precipitation for hydrologists. CoCoRaHS, the USGS and other groups use the water year as an alternate to the calendar year for watching for droughts and floods.
