In Peru, the last decades have been characerized by both significant population growth and diminution of the hydrologic reserves. During the decade of the 1980s, glaciers have undergone an acute retreat, a phenomenon that continued during the 1990s, implying the loss of important water resources. During the same period, water demand for human consumption, irrigation, hydroelectric power stations, etc., has largely increased, inducing tensions between the users.
The recent disputes between the regions of Arequipa and Moquegua on the Great Inn dam reserves, are tangible signs of the increasing tension over this vital resource. Thus, there is a need to inventory the resources available and planning its management in the long term, within the framework of the concept of Sustainable Development. Long-term planning requires evaluation of trends on both population and resources, taking into account potential climate change patterns.
Significant populations are living in the nearby valleys. Since precipitation occurs during part of the year, the surrounding villages are dependent on melting water from the Coropuna. There is a critical need to estimate remaining mass and retreating speed as an early warning for water supplies, allowing planners to take appropriate adaptation measures.
The water reserves are concentrated in the high mountain zones in the form of glaciers and lagoons. Due to the altitude and to rough topography, access to these zones is difficult, hence resulting in strenuous (and costly) missions for direct measurements. In such conditions, remote sensing technology is a cost-effective way of monitoring the evolution of the hydrologic resources. However, if these techniques limit the number of mission, in situ measurement are still needed for actual depth evaluation (impossible via remote sensors).
The German Cooperation Program (GTZ) has mandated a team from the University of Geneva and DEWA/GRID-Europe to assess the effects of global warming on the Coropuna glacier (alt. 6425m) in Peru. The team, composed of Walter Silverio, Christian Herold and Pascal Peduzzi, has been performing satellite image analysis, in situ measures, GIS modelling of remaining ice and statistical analysis for evaluation of trends.
A multi-temporal image analysis of Coropuna glacier was carried out, allowing a general vision of the temporary and space distribution of the water reserves. Although the use of passive sensors provides useful information on the ice and lagoon area, one needs active sensor (radar) images to produce 3D Digital Elevation Model (DEM). The variation through time of the DEM provides information on the ice mass losses/gains through time. However, these technologies are recent and only available since the 1990s, and do not provide information on remaining ice mass, for which ground measurements are still necessary.
The purpose of the mission on the Coropuna glacier was to use a ground penetrating radar for estimation of the remaining ice. The device sends electromagnetic waves, that echo on the bedrock, providing information on the depth of ice. The in situ measures were taken during a two-week mission in August 2004. Despite difficult climatic conditions, DEWA/GRID-Europe’s team collected 10 km of profiles geo-referenced using a Ground Positioning System (GPS). These measures will be used for calibrating a model of mass estimation.
Once completed, the study will provide information on retreat speed, impacts from global warming and estimated remaining period with ice. Depending on the results, programs for adaptation will be implemented by local agencies with support from GTZ.