A first National Inventory of Future Glacier Lakes: implications for water and risk management in Peru

Introduction

Anticipating new lake formations represents an important step towards the identification of both, new possible water storage options and potential hazards. This is particularly crucial in the Peruvian Andes where water scarcity is a common, and, most likely, an increasing issue, particularly in the dry season (May-September) when (dwindling) glacier contribution to river streamflow represents a major component of water supply.

On the one hand, the water use potential of new lakes developing within the near future needs to be further explored for main sectors of water use. On the other hand, new risks associated with rock and glacier instabilities and lakes increasingly exposed to landslides, avalanches and rock falls or ice detachments, have to be considered for downstream populations.

In this context, the new inventory “Projection of future lakes in the Peruvian mountain ranges” which was performed as a close collaboration of University of Zurich and the Glacier and Lake Evaluation Department (National Water Authority of Peru – ANA) within SDC’s funded Glacier Project+, represents an important step forward. It provides a tool for prospective and integrated risk, water and land management within a context of hydroclimatic and socioeconomic impacts.

Methodology and how to interpret the results

The applied methodology is based on numerical ice thickness distribution and bedrock modelling with the GlabTop (Glacier bed Topography) model (Linsbauer et al. 2012) using a simple empirical parameterization scheme with underlying complex glacier mechanics (Haeberli and Hoelzle 1995). This tool allows for reasonable estimates and evaluation of potential future lakes as far as a visual inspection protocol based on geomorphological criteria and confidence levels is been taken into account (Colonia et al. 2017). The results are most robust for the location rather than the precise area, depth and volume of potential lakes. Thus, the inventory needs to be understood as a first order of magnitude (±30% uncertainty range) which at least provides a good estimate of new potential sites of lake formation. However, only about 70% of the modelled sites might represent reasonable locations of long-term lake development due to dynamic processes, such as sedimentation of recently exposed depressions.

Main findings and perspectives

• 287 sites of potential future lakes (>1ha) have been identified which would be distributed within 11 out of 18 glaciated mountain ranges in Peru.
• Total lake volume would be about 231 millions of m³ which corresponds to about 0.5-1.0% of the entire estimated glacier volume in Peru (~38 km³). While at national scale this might not be much, locally the projected water storage might play an important role
• A major number (175) of the identified lakes has already developed or would be forming within a few decades which highlights the urgent need to perform more and improve studies on that topic and promote integrated risk, water and land-use planning within a timely manner
• A major development would be observed in the Cordillera Vilcanota (Cusco, southern Peru) due to the relatively flat terrain which favours lake formation in deglaciating bedrock depressions The present study represents a first effort to identify potential future lakes in Peru based on the National Glacier Inventory (baseline 2003-2010). Follow-up studies should use new data (e.g. new Glacier Inventory from INAIGM, baseline 2016; new DEMs, etc.) and additional methods to corroborate and update results within a rapidly changing Andean environment.
• Future studies should focus on some of the identified lakes in more detail for a realistic evaluation of water supply as well as risk potentials with e.g. geodetic in-situ techniques

Links to the new Future Lake Inventory for Peru:

• http://repositorio.ana.gob.pe/handle/ANA/3597
• https://www.researchgate.net/publication/333679681_Proyeccion_de_Lagunas_Futuras_en_las_Cordilleras_Glaciares_del_Peru

Further reading:

Colonia, D., Torres, J., Haeberli, W., Schauwecker, S., Braendle, E., Giraldez, C., & Cochachin, A. (2017). Compiling an Inventory of Glacier-Bed Overdeepenings and Potential New Lakes in De-Glaciating Areas of the Peruvian Andes: Approach, First Results, and Perspectives for Adaptation to Climate Change. Water, 9(336), 1–18. https://doi.org/10.3390/w9050336

Haeberli, W., & Hoelzle, M. (1995). Application of inventory data for estimating characteristics of and regional climate-change effects on mountain glaciers: a pilot study with the European Alps. Annals of Glaciology, 21, 206–212.

Linsbauer, A., Paul, F., & Haeberli, W. (2012). Modeling glacier thickness distribution and bed topography over entire mountain ranges with glabtop: Application of a fast and robust approach. Journal of Geophysical Research: Earth Surface, 117(3), 1–17. https://doi.org/10.1029/2011JF002313