National Water Authority of Peru

Acceleration of glacial melt has severe implications for water-food-energy security and inter-connected livelihoods of vulnerable populations in river basins fed by glaciers. For example, in the Ancash Region of Peru, glacial melt from the Andean Mountains provides up to 67% of dry season water supply going up to 91% during extreme drought (annual average 19%). Rapid retreat of glaciers in the Cordillera Blanca has already had notable impact on that supply, with evidence to suggest the majority of rivers now exhibit decreasing dry-season discharge i.e. have reached and passed 'peak water'. Challenges associated with a reduced supply of water to downstream agriculture, industry and hydropower generation are exacerbated by enhanced sediment and contaminant flux in extreme wet season floods. Climate change impacts compromise ecosystem service provision at times of both augmented low and high flow. While low flows and water supply are being increasingly impacted by the huge loss of water storage in shrinking glaciers, ENSO-related extreme events are leading to catastrophic delivery of excess water and sediment during high flows which compromise water and environmental quality downstream. Climate change is driving a hydrological regime of extremes with no advantage at either end: from supply and quality issues at low flow to more water than the system can handle at high flow, compromising water and soil quality downstream. Understanding the changing dynamics of glacial melt, hydrology and regional climate change is crucial in order for the design of infrastructure solutions and planning to be effective and resilient. Responsible, efficient and sustainable water use is necessary in national and transboundary watersheds, to ensure adequate supply and mitigate emerging quality problems. In order to achieve this consultancies and advisory organisations require high quality robust scientific evidence to underpin their design decisions for watershed management. This entails moving from (inefficient) sectorial management of water to a more integrated and holistic approach that takes into account the need for conserving ecosystems services. Indeed, while the Peruvian Congress passed a historic Ecosystem Services law in 2014 to take a holistic approach to tackling these challenges, implementation of integrated action to achieve Sustainable Development Goals has been hampered by a lack of evidence of glacial-fed watershed processes and function. While studies to date have been conducted in the Cordillera Blanca in relation to dynamics of glacial retreat, associated natural disaster risk, hydrology and past glaciations we do not have a sufficiently holistic and integrated knowledge of the wider impacts of glacial melt on current and future ecosystem service provision which is hampered by complexity of human-environment feedbacks, a knowledge base essential for mitigation of future uncertainty and risks. We propose that a basin-wide understanding of water, sediment and contaminant budgets within Peruvian glacial-fed basins is required to bring policy change for socio-economic benefits through (a) offsetting storage lost from shrinking glaciers through augmentation of mountain ecosystem service provision for landscape water retention and (b) providing the foundation for adaptive management strategies to support and enhance livelihoods under threat from high flows and downstream environmental quality consequences. This research is essential for the design of large-scale energy infrastructure, such as hydropower in glacier-fed regions. Likewise, bringing back and maintaining a balance between sustainable livelihoods and the environment is critical to build community resilience to environmental change.

The Peruvian Andes is home to 71% of the world's tropical glaciers, and the meltwater they supply is an essential resource for people downstream who depend on it for irrigation and sanitation. Further, hydropower plants driven by glacial meltwater provide more than 40% of Peru's electricity. However, Peru's glaciers are receding rapidly, threatening this supply, as well as releasing sediment to valley areas and revealing topographic depressions that may become natural reservoirs for glacier runoff. These thawing landscapes are also very active and can pose risks to downstream people and infrastructure. PEGASUS will assess the opportunities and threats that rapidly evolving landscapes, and natural resources, will bring to the people and businesses of three glacierised Cordilleras of the Peruvian Andes - Urubamba, Vilcabamba and Vilcanota - and make recommendations that will maximise the potential prosperity that can be gained in the face of continued environmental change. Modelling the climate of mountain catchments such as those in Peru is complex because of the interaction of large-scale weather systems with local-scale winds and extreme relief. Uncertainties in modelling the climate feed into projections of glacier change, which themselves are limited by a lack of data on previous glacier behaviour for calibration, and downstream river flows for validation. Robust climate modelling is also required for predictions of permafrost (freezing) heights, which are a key control on ice and bedrock stability, and thus avalanche risk. PEGASUS will produce new and refined projections of climate that will drive cutting edge glacier and permafrost models, to yield firm predictions of how the glaciers and freezing levels will change on a 5-yearly interval from now until the end of the century. As the glaciers recede and hillslopes become more active, sediment will be released into the valleys, and lakes will develop where ice existed. Some of the sediment will be trapped within these glacial lakes, and some will be transferred downstream by river flows. The rate of sediment release by glaciers in advanced states of recession is poorly known, and the role of lakes in capturing the sediment is also poorly quantified. PEGASUS will perform field measurements and modelling to improve understanding of the role of glacial lakes in removing, conveying and storing sediment being released from the glaciers, and characterise the impact this will have on downstream water quality and critical hydropower infrastructure. The locations of future glacial lakes can be predicted by modelling the thickness of the current glaciers and identifying subglacial depressions that will be revealed as the ice recedes. Using a Digital Elevation Model (DEM) of this ice-free terrain, it is possible to make a quantitative assessment of the hazard that these new lakes, as well as existing glacial lakes, pose to downstream areas if they were to burst catastrophically. PEGASUS will carry out this assessment for the largest lakes in the Urubamba-Vicabamba-Vilcanota study area and then undertake additional fine-resolution and physically-based numerical modelling to robustly quantify the effects of flooding and debris flows on people, land, the downstream river dynamics, and hydropower infrastructure. PEGASUS will then identify the barriers and opportunities that exist to the use of these lakes for water storage and hydropower development. This assessment will integrate consultations with government (CORECC), a large hydropower company (EGEMSA) and, crucially, communities living in the catchments of the lakes we have analysed. The recommendations that follow will provide information on the sustainability of existing and future hydropower schemes, how to manage water use in future decades and formulate policies that reflect the needs of all stakeholders, and the potential hazards that unstable mountain environments may pose to lives and livelihoods in future years.

The most sensitive glaciers to climate warming in the 21st century are situated in tropical mountain regions, and thus, serve as valuable sentinels of climate change. Most attention to date has focused on the quantity of meltwater released from these glaciers, because of the impact on global sea level and water security. The concurrent changes in water quality are much more poorly constrained, but have implications for drinking water, agriculture and industry. Peru holds 71% of all tropical glaciers, all of which have undergone high rates of mass loss and retreat in the last two decades. However, certain rivers fed by glacial meltwater are becoming acidic, with concentrations of metals often above World Health Organisation standards. This is thought due to the exposure of metal-rich (sulphidic) rocks in retreating glacier forefields, which release sulphuric acid and metals once oxidised - this acidity can no longer be neutralized by the intense chemical weathering which takes place beneath glaciers. The overarching hypothesis that CASCADA will test is that glaciated catchments in the Cordillera Blanca are evolving along a trajectory from pristine conditions, where glacial runoff is an important nutrient source for downstream ecosystems ("treat"), to those in which the same runoff is toxic to ecosystems and human health ("toxin"). CASCADA unites Peruvian experts in water resources, glaciology and ecology with UK geochemists, glaciologists and technologists to investigate and generate solutions to the cascading impacts of glacier retreat on water quality in Cordillera Blanca rivers. It employs cutting edge in situ monitoring technologies to capture first time data on the year-round quality of Cordillera Blanca rivers and to develop and test a novel wetland management model to remediate rivers with high metal toxicity. A strong partnership with local water users' committees under a citizen science scheme and the formation of an engagement board with governmental institutions and local communities will ensure capacity building and the transfer of technology for integrated wetland management and water quality reporting. Thus, CASCADA provides the transformative process understanding required to deliver a step jump in our ability to predict water quality evolution in deglaciating terrains and to develop effective solutions to toxic catchments.

Life on land depends upon freshwater. Mountains act as water towers, producing water by lifting moist air, and by providing temporary surface and below-ground storage of water for later release into rivers. These stores are particularly important in regions that experience seasonal droughts, as snow and ice melt can counteract reduced rainfall during dry spells. Two main natural depots of frozen water exist. Snow is a short-term store, delaying the release of water after snowfall on daily to seasonal timescales. Ice melt also releases water seasonally. However, glacier ice is a longer-term reservoir, storing water for decades to centuries. A similar behaviour can be observed in the non-frozen part of a mountain catchment. Stores such as wetlands, ponds and shallow below-ground flow provide short-term storage, while lakes and deeper groundwater show long-term release characteristics. The combination of these different processes determines the magnitude and behaviour of a mountain range's water tower function for the surrounding area. This is particularly important in the Andes, where some of the most important water towers of the globe are found. The human population in regions neighbouring the Andes depend on mountain water resources for drinking, food production and hydropower, as do animals and plant life. Unfortunately, human-induced climate change is altering the stores of water held in the Andes water towers. Greenhouse gas emissions mean that snow-bearing weather conditions are becoming less frequent, depleting the stocks of snow held in the mountains. The lack of replenishing snow, and increasing temperatures, are causing glaciers to lose the ice they store, retreating to the higher and colder portions of the mountains. In combination with climate change impacts on the rest of the catchment, this is contributing to water shortages across the Andes. Ongoing droughts are hitting high-population cities, where the concentration of people increases the demand for water. For example, the cities of Lima and Huaraz (Peru), La Paz (Bolivia) and Santiago (Chile), are all situated in catchments where snow and ice melt contribute to river flow. However, upstream rural areas, which are less adaptable to climate change, are often even more directly reliant upon snow and ice meltwater. This impacts irrigation for agriculture, stressing the food security of the region. To help manage these changes to water supplies, this project aims to achieve two things. The first is to provide better monitoring. The high altitudes of the Andes are poorly instrumented. To work out where and how fast conditions are changing, we will install more scientific instruments to measure snow, weather and river discharge. To contextualise the changes we can measure now, we need longer observational records extending back in time. Many glaciers have been retreating since 1850, leaving behind an imprint in the landscape which we will map. Using satellite imagery, we can track the retreat of these glaciers from the 1970s to their present position. We will also utilise records of past climate conditions, recorded by sailors in ships-log books and stored in the landscape in sediments. Our second goal is to project future changes, which requires computer models of climate, glacier and river processes. Such projections are required for policy makers, who need to be reliably informed of potential future change. We will combine state-of-the-art models, to simulate the changing water resources in ten Andean catchments. To assess the skill of our models at making predictions, we will test them against our observations of past conditions and current changes. Models that perform well at replicating observed conditions will be used to project a range of possible future climate scenarios. By combining these observational and model-based approaches, we will improve the approach to projecting water resource change, and help to inform water management plans.