From above, it looked like dregs in a coffee cup. Emerald green dregs. Green because the nutrients in the lake are so concentrated now that it’s only 10 to 20 centimeters deep.
Lake Waiau, the most sacred water body in Hawaiian culture, is close to disappearing.
“We’re losing this lake,” Lisa Hadway told the Natural Area Reserve System Commission at its meeting in November. Hadway heads the Big Island branch of the NARS and has been watching with despair the lake’s rapid decline in recent years.
At 13,000 feet above sea level, the lake sits within the Mauna Kea Ice Age NAR. Because of the lake’s cultural significance, researchers with the University of Hawai`i at Hilo’s Department of Geography and Environmental Studies have used various imaging techniques — from expensive LiDAR technology to a compilation of regular snapshots of the area — to monitor water levels and identify water sources, rather than entering the lake.
They’ve found that some of the lake’s lowest levels ever are being recorded right now, UH-Hilo professor Donna Delparte said at last year’s Hawai`i Conservation Conference in Honolulu. The lake is a small fraction of the size it was in October 1977, when Hawai`i experienced its last significant drought.
At the time of the conference, in early August, the lake was about four feet deep at its deepest point and most of the lake was less than one foot deep, she said. It had been twice the size in June, according to one of her maps.
By late November, the lake had shrunk even further. Groans and gasps filled the NARS Commission’s meeting room when Hadway showed pictures of the decline since the summer.
“I was stunned when I saw that,” Hadway said of the most current picture, showing little more than a large green puddle. “It’s an El Niño year. If there’s not a lot of snow …,” Hadway trailed off.
“Maybe we could rent a snow machine,” commission member Sheila Conant said.
The UH-Hilo team is investigating whether the mountain has experienced similar drought periods and has invited the public to submit old photos of the lake area so it can develop a more detailed record.
“There’s significant concern about what’s happening to the lake and lake level,” Delparte said at the conference.
The weekly column for September 13 written by USGS scientists at the Hawaiian volcano observatory notes that it’s unclear exactly what is causing the lake’s decline. The cause depends on whether the impermeable layer below the lake that prevents it from draining is made of permafrost or ash.
If it’s permafrost, then the lake’s decline could be a result of the permafrost melting.
“In this scenario, the lake would surely disappear as the permafrost continues to melt with increasing temperatures on Mauna Kea. The temperature increase is about three times faster than the global rate, and is observed at high elevations throughout Hawai`i,” the scientists state.
The more likely scenario is that the lake is maintained by an ash layer and that the lake is simply evaporating as a result of rising temperatures and the current drought, they write.
“Although the rising temperatures do not bode well for the future of Lake Waiau, a winter season rich in storms will do much to replenish the lake, as well as provide us with magnificent views of the snow-capped volcano,” they conclude.
A report for the 2012 Pacific Islands Regional Climate Assessment, released early last month, notes that the Hawaiian alpine ecosystems “are already beginning to show strong signs of increased drought and warmer temperatures, apparently related to increasing persistence of the trade wind inversion … since the 1990s.”
— Teresa Dawson
Volume 23, Number 7 2013