Even the Southeast rainforest can be in a drought
June 28, 2018
The Southeast Alaska rainforest is in a moderate drought, according to the National Weather Service. Not necessarily Haines, but the overall area.
A drought in a rainforest is difficult to predict and less easy to define than droughts elsewhere, said Rick Thoman, Alaska Region National Weather Service climate science and services manager stationed in Fairbanks, speaking in a climate assessment and policy webinar June 12.
There can be a drought even if it’s raining as long as there is a shortage of rain or snow accumulation over an extended period of time.
Additionally, droughts are defined in context of how they affect people, Thoman said. “A precipitation deficit isn’t just taken raw. It’s the impact to people’s activities — to generating power, to farming, or to the natural ecosystem.”
One impact has already hit Haines. Alaska Power & Telephone had to run its diesel generators for a week and a half in late April due to low water levels for hydropower generation serving Haines and Skagway, said Darren Belisle, the company’s power operations manager for Upper Lynn Canal.
The utility had to burn 40,000 gallons of fuel at a cost of about $150,000, which was passed on to ratepayers through a fuel surcharge, Belisle said.
This year’s precipitation has been well below normal. Accumulated precipitation at the Haines airport as of the end of April, measured by the National Weather Service, was 9.2 inches compared to the normal 15.4 inches.
Hydropower systems were running at one third their usual maximum until the water runoff showed up about three weeks late, Belisle said. That allowed the plants to increase their generation and shut off diesel power as of May 5.
By June 25, accumulated precipitation at the Haines airport was closer to average, with 14 inches compared to the normal 18 inches.
Besides hydropower generation, it’s difficult to easily measure direct impacts of a drought, said Aaron Jacobs, a hydrologist with the Weather Service in Juneau.
Jacobs said fisheries health, water supply, winter sports and rainforest health could all be affected by drought, which can cause economic impacts such as job loss, decreased tourism, food resource loss and environmental degradation.
While all of Southeast Alaska is a coastal temperate rainforest (one of seven in the world), Southern Southeast has seen more severe effects of drought than Northern Southeast.
The Haines and Skagway area is its own climate division, an area similar in climate as defined by the National Center for Environmental Information.
The northern panhandle is the smallest of 13 climate divisions in the state. Haines averages a meager 49 inches per year compared to Southern Southeast, which gets 60 to 160 inches.
Wrangell has been the hardest hit by drought and the borough has declared water-supply crises the past two years.
Ketchikan and Prince of Wales Island have encountered hydroelectric power generation troubles similar to Haines.
“We don’t see the effects quite as bad,” Belisle said, because Haines and Skagway’s hydropower is generated on the Kasidaya Creek and Lutak River, which run from snowmelt, in addition to Goat Lake.
“Once we start running out of ice, then that’ll be bad. The ice is basically a big battery for us.”
One of the most commonly used measurements for a drought is labeled the standardized precipitation index (SPI). The SPI puts departures from normal rain levels into context by comparing them against all the years of data ever collected (for Alaska, that’s since 1925).
For the mathematically minded, SPI is a standard deviation, which means that it shows a significant change from normal.
The Northern Panhandle was in a dry spell more significant than other dry spells in the six-month period starting in September (SPI of -1.4). Southern Southeast had a dry spell that was twice as significant as the North’s (SPI of -2.6).
“It’s the biggest indicator of drought since 1925 in weather history data,” Thoman said.