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Rainfall statistics tied to 'wet season'

On the weather page, why doesn't the Mail Tribune list the precipitation by the calendar year, from Jan. 1 to Jan. 1? It seems like it would be much more orderly. I know you do it the way you do because it has something to do with agriculture. Maybe you could do it both ways. I know it would require a little more arithmetic for somebody, but I'm sure you could handle it.

— David P.,

Central Point

David, we appreciate your confidence in our arithmetic skills, misplaced as it may be. Most of us here at the Since You Asked Department of the Numerically Challenged took up journalism when it dawned on us that if we couldn't balance a checkbook, a career as a statistical analyst probably was not in the cards.

Fortunately for us and our good readers, the National Weather Service takes care of all the higher math when it comes to weather stats. The math-savvy folks there, like meteorologist Brian Nieuwenhuis, also are patient in answering our questions, so we went back to the well, so to speak, to get your answer.

In the West, yearly water totals are often kept for the 12-month period of Oct. 1 through Sept. 30, which is referred to as the water year or, Nieuwenhuis notes, the "wet season."

"That's because we get our rainfall on both sides of the end of the calendar year," he said. That means that the use of the calendar year doesn't really show what the wet season was like, because the most significant rainfall amounts would come in two time periods that are separated by six or seven months.

You are right, David, there is an agricultural connection. The rainfall that occurs accumulates in part in the mountain snowpack and later in area reservoirs. So the total that falls during the wet season is a good indicator for what lies ahead for people dependent on that stored water.

The use of the October-September water year is not a universal one. The U.S. Geological Survey uses it, but it's not a standard for all water watchers. In fact, Nieuwenhuis says, it was new to him when he arrived here.

"Back east, where I come from, I'd never heard of it before," he said.

Use of the wet season measuring makes more sense in climates like ours, in which there are distinct wet and dry seasons (this year notwithstanding), he said.

"Elsewhere it rains more all year long; there's not that much of a difference."

But just to show the agency's math skills, the weather service keeps records both ways, for the calendar year and the water year. Thus the recent reports that the 2013 calendar year was the driest on record locally.

So, to your suggestion, David, can the Muddy Tributary run both numbers? It might be possible — we'll suggest it to the powers that be and hope they don't throw cold water on the idea.

Send questions to "Since You Asked," Mail Tribune Newsroom, P.O. Box 1108, Medford, OR 97501; by fax to 541-776-4376; or by email to youasked@mailtribune.com. We're sorry, but the volume of questions received prevents us from answering all of them.