The calendar may not say it’s 2025 yet, but for “water wonks” (those folks who are really into hydrology), it is! The 2025 Colorado River Water Year runs October 1, 2024 to September 30, 2025!

Why does the Water Year work that way?

Hydrologists have chosen October as the start of the water year because as the leaves start to turn, snowfall may begin. Precipitation that begins in fall accumulates through winter, which spans one calendar year to the next. Winter snow accumulation is particularly important in the Colorado River Basin, where ~70% of Colorado River flow originates as snowmelt. As seasons continue to change, spring and summer rainfall add to the total precipitation. Precipitation that falls during a water year reflects how much water will contribute to actual stream flow and groundwater inputs for that year.

As we start the cycle for this new water year, we’re hopeful that Water Year 2025 brings us more snow than Water Year 2024, which was slightly above average in terms of snowpack, but unfortunately below average in terms of runoff. However projections indicate that El Nino may no longer prevail and that we may see a La Nina year, which typically means dry conditions for the Colorado River Basin.

Time will tell!