Pinatubo lake unfit for swimming

CLARK FIELD, Pampanga — From blue to bluish green, the waters of Mt. Pinatubo’s crater lake have turned into dark brown, almost black, prompting government volcanologists to advise tourists to refrain from swimming in the lake or drinking the water.

Jaime Sincioco, resident volcanologist of the Philippine Institute of Volcanology and Seismology (Phivolcs), said the discoloration was first observed last Jan. 22.

Two days later, tourists who trekked to the Pinatubo crater expressed alarm over the almost blackened waters of the crater lake, which has a diameter of about two kilometers and which has become a major attraction in Central Luzon.

A Phivolcs quick response team, which examined the crater lake last Jan. 29, confirmed that the lake’s waters had indeed changed to "dark brown, almost black."

According to Sincioco, the lake’s waters used to be bluish to blue-green and at times milky depending on the climate or the occurrence of landslides within the crater.

Sincioco said the Phivolcs and the Department of Science and Technology will issue today an advisory urging Pinatubo trekkers "to refrain from swimming in the lake and from consuming its water until further notice."

At present, the Phivolcs, with the help of the DOST and the University of the Philippines’ Institute of Biology, is undertaking more exhaustive studies to determine "the most probable cause of the lake’s discoloration and assess any potential hazards it might pose," he said.

Sincioco, however, clarified that the change in color "does not indicate any renewed volcanic activity," saying they have not recorded any "anomalous earthquake activity" at Mt. Pinatubo.

"The level of seismicity (of Mt. Pinatubo) is considered normal since the volcano entered a period or repose after 1995," he said. The volcano erupted in June 1991.

Sincioco said the change in color could be due to algae and lichens, citing reports that tadpoles and leeches have been observed in the crater lake in the past months.

But Phivolcs is considering several factors, including "several near-surface events." — With Felix delos Santos