The Glacial Lake Handbook: Reducing Risk from Dangerous Glacial Lakes in the Cordillera Blanca, Peru
This technical report covers lessons learned by Peruvian engineers who have worked for more than 70 years on glacial lake management methods. The peer-to-peer format of the report shares technical lessons learned to help the global community addresses its own glacial lakes challenges. As one example, the report outlines surveying and engineering method lessons learned from facing past glacial lake outburst floods (GLOFs) in Peru’s highest mountain range, the Cordillera Blanca. With Peru’s decades of experience managing glacial lakes, the report authors compiled 16 case studies from lakes in Peru to help advance adaptation work in high mountains regions.
The report authors stress that local efforts must adapt to the unique context of each country, lake, and valley, and that each case requires action based on the best locally available knowledge and engineering. Overall, The Glacial Lake Handbook presents an overview of glaciers, glacial lakes, and management practices in Peru, including a history of Peru’s Glaciology Unit, a review of factors that influence risk management of glacial lakes, the methodology for reducing risk from dangerous glacial lakes, and the geological and historical background to case studies in the Cordillera Blanca. Implemented into the glacial lake management process is a wide range of disciplines including geography, climatology, anthropology, animal science, and botany, as well as the social and political sciences.
Methodology for Reducing the Risk From Dangerous Glacial Lakes:
- Create an inventory of glacial lakes.
- Carry out an initial assessment of lake characteristics including surrounding glaciers. This assessment includes topography, basic geology, basic glaciology, and profile analysis in cases where ice is in contact with or could be inside the moraines.
- If the initial assessment finds characteristics that indicate downstream risks, further study is warranted. This includes cartographic and bathymetric studies of the glacial lake and surrounding terrain, glaciological studies of all snow and ice that could affect the lake, geological studies, and analyses of soil mechanics. These studies should begin to address potential safety measures.
- Analyze the hydrology of the watershed. This determines safe discharge levels for the design of overflow canals, allowing for safe removal of excess lake volume. Wherever feasible, safety efforts should be combined with water development projects for lakes. This allows hazard mitigation to go hand in hand with resource management.
- Establish logistical access. The distance that tools, construction materials, food, and other supplies must travel (especially by foot, horse, or helicopter) is an important element in cost analysis and time planning.
- Implement safety measures based on information collected from the in-depth studies. Safety measures include volume reductions, hydraulic infrastructure such as open canals, and drainage tunnels or channels that will be covered by a rebuilt dam to contain potential surges caused by falling ice.
- Maintain the highest standards in construction. Peru’s experience is that sometimes the safety infrastructure is not put to the test until many decades after its construction. This highlights the need for following sound engineering standards that will maintain effectiveness for decades.