Hawaii - Lake Waiau, on the summit of Mauna Kea, is shrinking fast

Located on Big island in the " Mauna Kea Ice Age Natural Area Reserve", the Lake Waiau is under close surveillance since 2010.

     Hawaii - Big Island - Mauna Kea as seen from the Mauna Loa Observatory - Photo Nula666

This small lake , located below the summit of Mauna Kea, is the only alpine lake in Hawaii. Despite its small size , it plays an important role in the ecology and local culture .

   Hawaii - Mauna Kea : Lake Waiau and the outlet stream in May 2005 - photo Karl Magnacca .

The professor of Geography, Donna Delparte previously assigned to the University of Hawaii at Hilo, and currently at the University of Idaho, recorded the recent changes with laser scanning and photogrammetry modern techniques. Prior to 2010, the surface of the lake Waiau fluctuated between 5,000 and 7,000 m², with a variability dependent from the recharge in winter by rainfall and snow, and evaporation losses .

Hawaii - Mauna Kea : the Lake Waiau in January 2012 - Credit photo: Office of Mauna Kea Management

  Hawaii - Mauna Kea : the remains of Lake Waiau September 26, 2013 - photo USGS / HVO
The scale is given by the men, on the lakeside - Note the proximity of the lake and the astronomical settlements.

In early 2010 , its surface began to decrease to as little as 115 m² in September 2013. Its maximum depth was about 3 meters in 2010 , it is no more than 30 cm. today ... which means that the current volume is less than 1 % of its normal value.
Examination of historical photographs taken over the last 100 years gives no indication of a reduction in size as observed today.

What are the factors that explain these unprecedented changes ?

Hawaii drought that began in 2008 and intensified in 2010 may take place in this lower level , seasonal inputs are less important.
The situation of " perched lake " of Waiau ( over 4,000 meters) is special : the water is held in a depression by an impermeable substrate, consisting of silty clay layers interbedded with layers of ash . Permafrost is suspected to underlie and surround the lake, providing a watershed that directs the water to the lake.

It is still difficult to support one or another hypothesis : reduced rainfall or changes in permafrost ... unless these variations are related to the activity of the volcano.

Hawaii - Mauna Kea : the remains of Lake Waiau in November 2013 - Photo : Office of Mauna Kea Management

Some native Hawaiians, attending the Mauna Kea and feeling spiritually connected to the sacred mountain, asked whether the decreased level of the lake was not a sign of imminent danger to this place . Many practitioners are indeed opposed to the development of astronomical facilities on the summit of the volcano.

Poli `ahu , ice goddess of Mauna Kea ... Pele is well alive in the background - drawing Herb Kane

In the Hawaiian mythology, Poli `ahu, whose name means " cloaked bosom  " , is the legendary girl of Wakea , ancestor of the Hawaiian . As goddess of snow, it is the antithesis of her rival , the goddess Pele.

Waiau , Poli `ahu sister, the guardian of the lake that bears his name.
She bathes Poli `ahu, and refreshes her drinking gourd with sweet water which she can fetch by using her bird form to fly from place to place.
 
Autel on Puu o Kukahauula , the summit of Mauna Kea. Can be seen in front of the altar on the left ( and inset ) the bench mark of USGS . - Photo Denys

Sources:
- HVO / Volcano watch – Lake Waiau is shrinking fast - link

- Global Volcanism Program - Mauna Kea

- USGS - The geology and petrology of Mauna Kea Volcano, Hawaii; a study of postshield volcanism - 1997, Wolfe, Edward W & al.