Climate change and accelerating glacier recession is affecting the water cycle and the future of water resources in the Peruvian Andes. In the Cordillera Blanca, the most glacierized mountain range in the tropics, the natural and social systems of the region are very dependent on glacial water resources and it is considered to be one of the most vulnerable to glacier-related water stress in the world. This interdisciplinary and collaborative research project will evaluate the new system of freshwater governance that is emerging in the Andes and how glacial dynamics are transforming melt water rates as they rapidly recede. The research will generate new insights into the coupled natural and human consequences of glacial recession in the tropical highlands by examining the combined effects of glacier recession on downstream watersheds, the resilience of livelihood systems and the ways in which economic change and shifting water governance are factors in this hydrologic, ecological, and social transformation. The research will also generate new hydrologic models and derive quantitative estimates of glacial water dynamics.
As glacier recession is accelerating in the Cordillera Blanca, dramatic changes in the Andean hydrologic regime pose significant challenges to Andean society. Data and observations from the project will inform water resource policy makers, global change specialists, development practitioners and scientists who study co-related topics such as chemical weathering and physical sedimentation. In examining of climate-glacier-water-society dynamics in the Cordillera Blanca, this research will provide critical information to urban residents, industries, farmers, and policymakers that will inform adaptive strategies and responses to global climate change. Integral to the project is a cross-cultural education and outreach plan that will increase awareness, inform policy managers, strengthen institutional partnerships, and educate the next generation of interdisciplinary scientists at both the undergraduate and graduate level.
The tropical Peruvian Andes are affected by a combination of natural and social alterations related to climate change. Our case study of how these interactions affect water resources has many implications for change expected in other mountainous areas affected by melting glaciers. Specifically, hydrological modeling done during this research shows that downstream discharge will first increase as glacier storage is released, and then decrease as the storage volume diminishes. "Peak water" represents a shift from increasing to decreasing discharge. Our research has shown that for Peru's Cordillera Blanca mountain range draining to the Pacific coast via the Santa River, most of the glacierized tributaries and the entire upper watershed have already passed peak water, contrary to other published prediction of future increases still to come. These streams now feature lower flows, especially in the dry seasons, and increased variability in discharge. We surveyed proglacial valleys using ground and satellite measurements and document ecological impacts of these changes as wetland area decreases. Nevertheless, we have shown that water usage has intensified in many sectors at the same time as this hydrologic shift has occurred over multiple decades. Because precipitation in the study region is highly seasonal, and the Peruvian coast is arid, glacial melt water from the Cordillera Blanca buffers discharge for the entire Santa River basin. Hundreds of thousands of people there rely on glaciers for water used for hydroelectricity, mining, irrigation, the tourism economy, and livestock production, and the glaciers also provide water to Peru’s second largest city (Trujillo). A diminished and less consistent stream flow threatens all of these activities, and also water quality as the dissolved and suspended load in the stream flow become more concentrated. With our transdisciplinary methodology including hydrology, geography, and environmental history, we have shown that the future availability of water resources in the Santa River watershed is limited by glacier retreat in the Cordillera Blanca, but also under unprecedented demand for water uses. The intellectual merit of our project arises from its linkages between biophysical and human factors to explain how and why stream discharges have been declining, why residents are reporting significant shifts in climate-glacier-water dynamics, and how human populations have been responding to these shifts. Through the development of a holistic hydro-social framework to understand the societal effects of climate change and glacier retreat, we offer a way to combine biophysical drivers on hydrology with various human-focused water withdrawal mechanisms. The project thus integrates the often-divergent analysis of water supply (the realm of hydrologists and glaciologists) with water use (the focus of social scientists). Results further demonstrate that both biophysical changes and societal forces play vital roles in shaping the future of water resources and water governance. Five major human variables should be integrated into future predictive scenarios of water resources in glaciated basins: (1) political agendas and economic development; (2) governance, including laws and institutions; (3) technology and engineering; (4) land and resource use; and (5) societal responses. This hydro-social framework has widespread implications for glaciated watersheds worldwide. Findings from this research project also have important broader impacts, especially for human populations downstream of the glaciers. This project shows the precariousness and vulnerability of economic development that relies on single intake canals in an area that has, historically, experienced some of the world's most deadly glacier-related disasters. The large Chavimochic irrigation project, for example, depends upon glacier-fed Santa River water not only for its export-oriented agro-industrial project, but also for potable water for Trujillo (~800,000 residents) and for the livelihoods of 60,000 agricultural workers. Declining glacier runoff for Chavimochic, this research demonstrates, has global importance because Peru is the world's leading exporter of asparagus, much of which comes from Chavimochic, among other crops exported to the United States. If the glacier-fed Santa River water supply continues to decrease as this project shows, or if an outburst flood or other glacier disaster damages the Chavimochic intake canal or the Cañón del Pato hydroelectric station, then nearly a million people will suffer from lack of drinking water, reduced energy for homes, loss of jobs, and a crippling of the regional economy. In addition to publishing articles and books, conference presentations, and public lectures in both English and Spanish, this research team has also widely disseminated results in Peru through lectures, consulting for Ministry of Environment and Ministry of Agriculture officials, and outreach with local communities. The researchers built and maintain collaborations with (1) Autoridad Nacional de Agua (National Water authority) and Unidad de Glaciologia y Recursos Hídricos (Glaciology and Hydrological Resources Unit) by sharing field instrumentation and data acquisition; (2) Instituto Geofísico del Perú (Peruvian Geophysical Institute) through logistical support and research collaboration; (3) IRD, France by sharing stream gage data; and (4) CHAVIMOCHIC by sharing river discharge and water quality data.
