October 13, 2015
Comparison of 1987 and 2015 Landsat images indicating retreat from red arrows to yellow arrows of 2.5 km and development of a new lake at the terminus. orange arrow indicates glacier dammed lake that fills and empties periodically.
Colonia Glacier drains east from the Northern Patagonia Icefield feeding the Baker River, Chile. It is the largest glacier draining east from the NPI. A comparison of the 1987 and 2015 images indicate a 2.5 km retreat of the glacier front, development of a large lake and areas of thinning well upglacier at the purple arrows. The recent substantial retreat of Colonia Glacier like Glacier Nef just to its north is posing new hazards. The glacier is unusual in the number of lakes that are adjacent to or feed into the adjacent glacier dammed or proglacial lakes. In the image below Lake A=Arco Lake, Lake B=East Terminal Lake, Lake C=Cachet 1 , Lake D= West terminal Lake, Lake E=Colonia Lake and Lake F=Cachet 2. In the case of Baker River the outburst floods are a threat to the planned hydropower developments as documented by Dusaillant and others (2009). Hidroaysen Project proposed 5 dams on the Baker and Pascua River generating 2750 MW of power that after initial permit approval in 2011Chile’s Committee of Ministers overturned the environmental permits in 2015.
Google Earth image from 2005.
The glaciers recent retreat and glacier lake outburst floods have been closely monitored by the Laboratorio de Glaciología in Valdivia, Chile. Aniya and others (1999) observed that Colonia Glacier began a rapid retreat after 1985 from 1997-2005 that has further accelerated, with a general frontal retreat of 2 km. Rivera and others (2007) observed that the Colonia Glacier had lost 9.1 square kilometers of area from 1979-2001, which is 3% of the total glacier area and thinned 1.1 m per year in the ablation zone.
Image from Laboratorio de Glaciologia, frontal change 1944-2005.
The Laboratorio de Glaciologia’s observed in the spring of 2008 Baker River suddenly tripled in size, in less than 48 hours, roads, bridges, and farms were severely damaged. Lake Cachet 2 had vanished the 5 square kilometer glacial lake had emptied 200 million cubic meters of water in just a matter of hours. This lake drained beneath the glacier after sufficient water had filled the lake to buoy part of the glacier and subglacial conduits had begun to develop. Since Cachet 2 emptied in April 2008, the lake has emptied at least six more times October, December 2008, March and September 2009, March 2010, and early 2013 with peak flows released of 3000 cubic meters per second. Below are images of Cachet 2 full iand empty in 2008 from Laboratorio de Glaciologia’s. Also a comparison of before and after drainage in Landsat images from Sept. 2012 and Feb. 2013.
Cachhet Lake full looking toward Colonia Dam 2008
Cachet Lake after emptying looking upvalley away from Colonia Glacier 2008.
Cachet lake full in Sept. 2012 and emptied in Feb. 2013 Landsat images.
The two lakes at the terminus of the glacier did not exist in 1979, the western most terminus lake drained into the easternmost terminus lake (D) via a sub-glacial tunnel after formation in the late 1980’s until 2005 when a channel was cut right through the glacier terminus. Retreat of the glacier terminus first led to significant lake development in 2001. This is evident in the image below, there is still glacier ice on both sides of this drainage channel. By 2015 the lakes have merged into a single large proglacial lake at the terminus that is 3.2 km wide.The development and demise of glacier dammed lakes and the resultant problem of glacier lake outburst floods is not rare today, Imja Glacier, and Tulsequah Glacier are other examples.
Lake expansion at the end of the Colonia Glacier from 2005 to 2013, Google Earth images.