Water Rock Glaciers and climate change in the dry Andes of Bolivia: implications for future water supplies

This project aims to investigate rock glaciers in the arid mountains of Bolivia and assess their future contribution to water supplies in the region. Mountain hydrology plays a crucial role in maintaining social and economic development in many arid regions of the world. However, climate change is leading to recession of mountain glaciers. In Bolivia mountain glaciers have undergone significant melting since the 1950s, and continued predicted warming over the 21st century will result in further glacier recession and eventual disappearance, especially where the glaciers are small. This glacier recession threatens the future water supplies for the cities of La Paz and El Alto, adversely affecting economic development and helping to drive social, political and ecological instability. However, in several of the high arid mountain regions in Bolivia considerable ice is enclosed within rock glaciers, elongate valley-bottom landforms comprising a variable mixture of rock debris and ice. These landforms are an important component of hydrological systems in many mountain systems, transporting large amounts of coarse and fine sediments to valley-bottom locations and forming extensive potential reservoirs of water. With a surface cover of rock debris, the ice content is insulated from low amplitude and high frequency temperature changes and, as a result, rock glaciers are predicted to respond more slowly than ice glaciers to climate warming. Consequently, they have the potential to play an important future role in hydrological systems under conditions of global warming, producing water supplies to mountain communities as glaciers undergo continued recession. Despite this, several obstacles stand in the way of a better understanding of the role that rock glaciers may be able to play in regulating mountain hydrology. First, there have been few systematic inventories of rock glaciers in mountain regions, despite the pressing need to assess the potential of rock glaciers to contribute to water supply. Second, while much is known of the recession of ice glaciers in response to climate change, much less is known of the rock glacier response. Third, there is as yet incomplete understanding of the amount of ice contained within rock glaciers, especially at the regional scale, and this hampers assessments of the importance of these landforms to providing water supply. As a result, this research proposal will address the first two of these problems and aims to provide a data base from which we can begin to answer the third. We will use remotely-sensed data to map the location, areal extent, and form of rock glaciers in the dry Andes of Bolivia over the last 50 years using fine spatial resolution (5 m) optical satellite data and freely available decommissioned CORONA data from the 1960s. We will use these results to assess rock glacier responses to observed climate change over this period which encompasses the time when attribution studies indicate global temperatures responded to greenhouse gas forcing (IPCC 2007).