Research: Long-term drought trends for Idaho

Credit: Melissa Stoner / KTVB

Research: Long-term drought trends for Idaho


by Rick Lantz


Posted on January 30, 2014 at 10:33 PM

Updated Friday, Jan 31 at 9:06 AM

BOISE -- It's no secret that Idahoans aren't seeing the snow and the rain that we're used to.

Snow pack levels are below average, and last year we dipped into water reserves to make it through the summer.

Idaho's Chief Meteorologist Rick Lantz went to find out if this drought will continue, and spoke to State Climatologist John Abatzoglou from the University of Idaho, whose office is always busy collecting weather information for the entire state of Idaho.

Over the years, he's gathered a large amount of information, and what he found is grim.

Normally, when we think of a forecast, we think of taking the latest weather information and creating a forecast.

"We have pretty good records for 1920 onwards for Idaho," said Abatzoglou, who has collected a large amount of information over the years.

Even if they lack information in some areas, nature also has a process of keeping weather records, like using tree rings to get records from before scientists started measuring.

"By combining these trees from across the region we can actually paint a picture of past droughts and also better understand how things like snowpack have changed," said Abatzoglou.

This chart that shows some of these changes that Abatzoglou has discovered.


The 1920s and 30s was a time of prolonged drought in Idaho, as you see by the block below the line indicating dry. The years from the late 1930s through the 1990s were generally above our line indicating that the period averaged above normal precipitation over a long period of time. The concern now is the second period of prolonged dryness the map indicates in our recent years. Could our dry weather be an repeat of the 1920s and 1930s? If so, does the climate of the last 100 years show a trend of any relief?

"We've had some pretty wet springs recently, that is actually one of the trends we do see. Four of the last five springs have been well above normal in terms of perception. We have a good history of playing comeback, and we are going to have to do that this year," said Abatzoglou.

So, if the weather runs in patterns as the climate suggests, then this spring should be a big help to our unusual dry weather.

According to Abatzoglou, this pattern also suggests that an El Nino pattern could develop next winter.

An El Nino is a pattern that brings dry weather to Idaho.

"We have an El Nino next year then we are talking about multiple drought years back to back and that's gonna have a significant impact on water supply," said Abatzoglou.

Another two years annually dry weather? Something we don't need.

Abatzoglou mentioned that we would need another 10 years of dry conditions to match those years in the 1920s and 1930s, and he also feels that we do have enough recorded weather history to have high confidence in the next couple of years but is hesitant to go beyond that for now.

Maybe with more recorded weather climate in the future, they may be able to extend the forecast out over 10 to 20 years.