KAILUA-KONA — Rain and snowfall continue to replenish Lake Waiau, keeping the alpine lake that sits some 13,000 feet above sea-level atop Mauna Kea nearly full or full for more than two years.
Just three years ago, in fall 2013, Lake Waiau, normally 1.7 acres, was shrinking fast due to a dry spell lasting several years, that rendered much of the lake bed dry, leaving just a puddle in its center.
Normally 100 yards wide, the U.S. Geological Survey reported the lake was just 10 yards wide and 9 inches deep on Sept. 26, 2013. By December, the situation had worsened with the maximum depth measured at 5 inches.
Researchers Matthias Leopold and Norbert Schorghofer in a June 2016 research paper on the subsurface architecture (geologic formations that hold water), said 2013 marked the first time the lake had disappeared from within Puuwaiau cinder cone.
When full, the lake has a maximum depth of about 3 meters, or 118 inches, according to photographic monitoring and data of Lake Waiau kept by state agencies since 2012.
A 2015 report by the USGS based on data from 1885 to 2010 found the lake’s surface area normally fluctuates between 5,000 and 7,000 square meters (1.23 to 1.72 acres). In late 2013, that number had dwindled to 114 square meters, far worse than amid drought in 1978, when Waiau dropped 4,100 square meters.
Today, Lake Waiau is nearly full, as it has been since fall 2014, indicative of normal precipitation in Puuwaiau near Mauna Kea’s summit, according to information from the Department of Land and Natural Resources Division of Forestry and Wildlife Mauna Kea Ice Age Natural Area Reserve and observations by the Office of Mauna Kea Management provided to West Hawaii Today by DLNR spokeswoman Deborah Ward.
“There were also good winter rains and snow at the end of last, and beginning of this year,” Ward said. Photos provided by Ward showed a good amount of snowfall, including the lake appearing to have developed ice on its surface during December.
Attempts to reach National Weather Service Hydrologist Kevin Kodama for additional detail on precipitation in the area were unsuccessful as of press time on Thursday. In an outlook issued in October, he expected near to above average rainfall through spring 2017 because of a weak La Nina event in the equatorial Pacific. That forecast also noted that the 2015 and 2016 dry seasons had been the wettest in 30 years.
Lake Waiau is a “perched” water body in which water is held in a depression by a continuous layer of fine material in its surroundings, which is covered by periglacial slope deposits. The fine layer acts as an aquifer that may gently release water into the lake over the year, according to Leopold and Schorghofer’s 2016 report. That report found that the fine-grained material, and not permafrost, as previously thought, is likely the impermeable material that perches the water table.
The study also determined that Waiau, which means “swirling water of a current” in Hawaiian, isn’t an anomaly. It also isn’t the highest lake of its kind in the Hawaiian Islands, they found, after establishing the existence of a second body of standing water in a nearby cinder cone, Puupohaku.
The lake falls within the 3,894-acre Mauna Kea Ice Age Natural Area Reserve created in 1981 and managed by the DLNR. Within the reserve’s boundaries are a number of significant geological, biological and archaeological resources managed by Natural Area Reserve managers.
Currently, staff are installing biosecurity/decontamination stations to allow visitors to scrape off mud and potential invasive weed seeds from their shoes as they arrive to visit the lake, in addition to ungulate removal and outplanting, according NAR manager Nick Agorastos.