Definition of ‘water year’ is fluid

By Doyle Hirsch
For the Daily Tidings
Posted Sep. 8, 2014 @ 6:16 pm

So it’s the first week in September and the beginning of what local meteorologists call a new water year. What are they talking about?
If you live in the U.S., say, east of central Kansas, where rain is generally abundant (40-plus inches) and falls throughout the 12 months, you never heard of the term. If you live west of the Rockies, where rainfall is generally 20 inces or less and most precipitation falls in the late fall and winter and early spring, often as snow at the higher elevations, you may be familiar with it.
It’s generally defined as the precipitation that falls from the beginning of the wet season in one year to the beginning of the wet season the next year in locations where municipalities and agriculture are dependent on snow melt for the water. The USGS determines this to be Oct. 1 of one year to Sept. 30 the next. It has nothing to do with the calendar year.
Seems simple, but in practice its implementation is erratic at best. The cities at the front range of the Rockies in Colorado and Uinta Mountains in Utah, which would seem totally dependent on snow fall for their water supply, use the calendar year, as do Phoenix and Tucson.
West Coast states — California, Oregon and Washington, plus Idaho — generally implement some sort of water year. But there’s no consistency.
Much of California starts its water year on July 1! That would appear to be in the middle of the dry season (though you could argue that every season is dry in California these days). But Redding uses the calendar year for some reason.
The coast, from Northern California through Oregon, uses the calendar year. The inland northwest consistently uses the water year and for places like Eugene, Portland, Seattle and Boise, that’s Oct. 1. But in Southern Oregon with significantly lower rainfall (except for the Ilannoy Valley), we inexplicably start on Sept. 1. September ain’t the start of the rainy season, Dick. Except for last September’s anomaly, the wettest September I’ve recorded and incidentally the wettest month of the 2013 calendar year, that month has consistently been the second driest after July. At this location my records go back to 1985.
So what does all this have to do with our drought? For the so-called water year I’ve got 84 percent of normal — not great, but it’s been a lot worse. For the calendar year, I’ve got 98 percent of normal. What’s happening here?
What’s happening is calendar year 2013. It was the second driest 12 months I’ve recorded — 15.32 inches, or 61 percent of normal. Only 1987 was drier and many of you will remember that smoke-filled late summer. Incidentally, the so-called water year for 2012-2013 was 94 percent of normal. We had a wet spring but there was very little snow in the mountains.
Essentially, the water year was pretty irrelevant. What I’m leading up to is that we need to have the local newspapers and TV stations start reporting both so-called water year and calendar year data (the Daily Tidings has carried the calendar year data for years, thanks to some enlightened individual). Most people were clueless about how dry it was — unless, of course, you relied on a well. A recent article about a very busy well driller in Josephine Country drove that point home
CoCoRaHs, a national precipitation data base out of the meteorology department at Colorado State University in Fort Collins, asks all members to report their water year data on Oct. 1!
It’s time for the Southern Oregon National Weather Service office to get in sync. It’s like a small section of a state that doesn’t use Daylight Savings Time. Also, the precipitation for the so-called water year and the calendar year can vary widely — I’ve had up to 10-inch discrepancies. Both are of equal value and need to be consistently reported by the media.
If we are to believe the climatologists, this year is more the rule than the exception — the Mt. Ashland Ski Association’s sanguine forecast for next year not withstanding.
This is the first in a periodic series of columns about Ashland-area weather by Doyle Hirsch, who compiles the precipitation and temperature readings appearing daily in the Tidings. Send weather questions and column topic suggestions to Hirsch via [email protected].