The peaks of Peru's Cordillera Blanca are home to the densest array of tropical glaciers in the world.
Runoff from that ice feeds the Rio Santa, providing most of the river's flow during the annual summer dry season -- water that is used for drinking, irrigating fields and generating power along a broad swath of Peru's Pacific coast.
It's a bounty that scientists and government officials have long expected to decrease as climate change shrinks the region's mountain glaciers. But a new study suggests that is already happening -- that decades earlier than anyone expected, the glacial runoff that feeds into the Rio Santa has passed "peak water."
"Two years ago, I had a discussion with the head of the glaciology office at Huaraz," said the study's lead author, McGill University doctoral student Michel Baraer. "We talked about the consequences of melting glaciers and water resource management. ... He said, 'We are before the peak, and we have only 20-30 years to adapt to these changes before we really see a negative trend.' What we have discovered now is that these 20-30 years do not exist. The peak is already past."
Baraer is part of an international team of researchers who used historical stream gauge records and satellite data to assess the state of the Cordillera Blancato's glaciers and their runoff into the system of tributaries that feeds the Rio Santa.
Their work, published in the January issue of the Journal of Glaciology, reveals that runoff from those glaciers has peaked and is now declining. Although the rate at which the glaciers are melting continues to increase, Baraer said, there is so little ice left that its melt will produce less and less runoff as time goes on. More
