Scientists at the Hawaiian Volcano Observatory say Lake Waiau, the tiny body of water just below Mauna Kea’s summit, has been shrinking at an alarming rate and has almost disappeared.

Since 2010 the lake has shrunk from about 1.2 to 1.7 acres to about 0.03 acres, 2 percent of its normal surface area, according to the observatory’s Volcano Watch edition this week.

Scientists say, based on historic photographs and written reports, that a drop of this magnitude hasn’t happened in the lake’s recorded history.

The lake had been about 3 yards deep, but the water level is now less than a foot, meaning the water volume has shrunk to about 1 percent of its 2010 size, according to measurements by former University of Hawaii-Hilo professor Donna Delparte.

Observatory scientists, Office of Mauna Kea Management rangers and state land and wildlife officials have been monitoring the disappearing water. But they are still trying to figure out why the lake is disappearing.

Drought may be a factor in the water loss, according to Volcano Watch.

"The Mauna Kea visitor center weather station shows very little precipitation for several consecutive months in early 2010, which may have been a trigger for the level drop that was sustained by low precipitation over the subsequent few years. The National Drought Mitigation Center shows that the drought across Hawaii intensified in early 2010," observatory scientists said.

But there could be other factors.

Lake Waiau is a "perched" water body, in which water is held in a depression by an impermeable substrate of layers of silty clay, interbedded with ash layers and possibly permafrost, the article said.

Scientists are also wondering if the permafrost that surrounds the lake may have altered the water balance.

Residents with historic photographs of the lake are being asked to contact scientists by email at askHVO@usgs.gov.

"Given its cultural significance and its uniqueness, the disappearance of Lake Waiau would be a great loss for Hawaii. The future is far from certain for Lake Waiau, and DLNR (Department of Land and Natural Resources), rangers, and scientists will continue to watch this situation," the observatory said.