What triples the volume of an already massive river? The Baker already lays claims to many superlatives: largest river by volume in Chile, draining from Lago General Carrera, the second largest lake in South America, and from the Northern Patagonian Ice Field, one of the largest extrapolar ice fields in the world. In the last five years, it has become the subject of the largest environmental fight in Chile’s history: the debate over HidroAysen’s plan to erect mega hydroelectric dams.
On January 27th, three Bakers-worth of water charged down the river as its flow rocketed 3,746 cubic meters per second (132,288 cubic feet per second) from a normal flow of around 1,200 m3/s (42,377 Ft3/s). The flood-stage volume exceeded the average flow of many of the world’s largest rivers: the Nile, the Missouri, the Yellow River of China, the Rhine. For most of a day, the Baker was running at five times the volume of the Hudson River in New York.
Where did this tsunami of water come from? For now, no industrial human interference. On January 25th, a glacial lake outburst flood (GLOF) began at the Cachet 2 lake, a vast, two-square-mile glacial lake in the Baker watershed. This lake drains from the Colonia Glacier, perpetually rising and falling according to the melt rate of the glacier and surrounding ice field. At certain moments, however, an accelerating melt rate raises water pressure and puts great stress on the ice dam that forms the end of the lake. Water forms a channel underneath the ice dam and into the Colonia River below. The initial trickle grows exponentially in volume, until the ice dam gives way to the stress. Within a matter of hours, the entire lake—all 200 million cubic meters of it—dump out, like water rushing down the bathtub drain.
The water of Cachet 2 then travels a brief way down the Colonia River before joining the Baker River. For several hours, the supercharged volume of the Colonia River pushes the Baker upstream at the point of confluence as it floods out in all directions. Some of us drove out through the Colonia Valley to see the effects: water covering farms and roads, and the river spilling over its banks. We visited the farm of the parents of park guard Daniel Velasquez, where high water had flooded bridges. Thanks to a radio-based early alert system, they had moved their livestock to higher group and so suffered few major losses from the flood.
The history of GLOFs in the Baker watershed tells a frightening tale even for a climate change skeptic. Historical records show periodic GLOFs in the area. Prior to 2008, however, the last recorded GLOF in the Baker watershed occurred four decades ago. Since 2008, six GLOFs have rocked the Baker. Scientists have well documented the accelerated melt rate of Patagonia’s glaciers, whose extrapolar location makes them particularly sensitive to small variations in climate patterns. At the 2010 climate change talks in Cancún, the United Nations Environment Programme (UNEP) released a report on mountain glaciers, stating that glaciers on Argentine and Chilean Patagonia are “losing mass faster and for longer than glaciers in other parts of the world.”
The increasing instability of the Baker river system raises yet another serious technical difficulty with the HidroAysen dam project. Even a large dam would struggle to withstand the added stress of a triple-volume of river. Moreover, GLOFs transport large volumes of glacial sediment downstream, which adds further stress to the dam system. While the natural breakage of an ice dam on Cachet 2 brings major floods to the area downstream, the failure of an immense manmade reservoir on the Baker would wreck havoc many times worse. As the Patagonia Sin Represas movement has demonstrated, HidroAysen paid little attention to the risks of GLOFs in their original project design. Our systematic critique of the company’s environmental impact statement highlighted this flaw, but HidroAysen has failed so far to give an adequate response.
Seven years into the campaign to save Patagonia’s rivers, the spectacle of the engorged and unpredictable Baker returned us to the wildest of a wild river. No scheduled release determined its volume and no reservoir caught the glacial outflow. Among the many reasons to oppose the dam project, the spiritual value of a wild river is one of the more difficult to price and evaluate. Yet spending time with the dynamic Baker produces an undeniable expansion of the imagination and spirit.
For more information in Spanish, see this article.