Rock glaciers as water stores in the Bolivian Andes: An assessment of their hydrological importance

Journal ArticleCopyright © 2015 University of Colorado at Boulder, Institute of Arctic and Alpine ResearchWater scarcity is a growing issue for high altitude arid countries like Bolivia, where serious water resource concerns exist because of climate change and population growth. In this study we use a recent Bolivian rock glacier inventory (Rangecroft et al., 2014) to estimate the water equivalent storage of these understudied cryospheric reserves. This paper shows that Bolivian rock glaciers currently store between 11.7 and 137 million cubic meters of water. Rock glacier water equivalents are compared to corresponding ice glacier water equivalent to allow an assessment of the hydrological importance of rock glaciers as water stores in this water scarce region. It can be seen that in the densely glaciated Cordillera Real (15°-16°S) rock glaciers form a small component of mountain water stores; however, along the Cordillera Occidental (17°-22°S), where ice glaciers are absent, rock glaciers are a more important part of the cryospheric water store, suggesting that they could be important for local water management. This is the first time that the water equivalence of the Bolivian rock glacier store has been quantified and is a first step toward assessing the contribution and importance of alternative high altitude water sources.NER

Rock Glaciers, Water Security and Climate Change in the Bolivian Andes

Water security in the Bolivian Andes is projected to decrease with population growth and climate change. As one of the poorest countries in the region, Bolivia is particularly vulnerable to such changes due to its limited capacity to adapt. Key gaps exist in our knowledge of the Andean cryosphere, including a lack of information on alternative mountain water sources, such as ‘rock glaciers’. The presence and hydrological importance of these cryospheric features is unknown for the Bolivian Andes. Yet, with current and projected [ice] glacier recession forecasted to negatively impact water availabilty, it is important to gather data and understanding on these cryospheric landforms. Consequently, this PhD has created the first rock glacier inventory for the Bolivian Andes, estimated rock glacier water stores, assessed their hydrological importance in comparison to glaciers and modelled the implications of projected rising temperatures on rock glacier activity and permafrost extent. This information has contributed to scientific knowledge about the Bolivian cryosphere and, more specifically, has increased knowledge of the frozen store of water in rock glaciers in the arid mountains of Bolivia where future water security issues are expected in response to climatic change. The rock glacier inventory for the Bolivian Andes was built through expert photomorphic mapping of freely available, high resolution satellite data (Google Earth), supported by a programme of field work during July - August 2011 and July - August 2012. A total of 94 rock glaciers were found to exist in the Bolivian Andes between 15° and 22° S, of which 54 were classified as active, estimated to contain between 0.05 and 0.14 km3 of water. At the national scale, research demonstrated that Bolivian rock glaciers were not as relatively important as hydrological stores when compared to estimations of glacier water equivalences. At the regional scale, three study regions were identified and analysed: Cordillera Real, Sajama and Western Cordillera. Along the Western Cordillera where glaciers are absent, the hydrological stores of the rock glaciers could be considered important. With current and projected glacier recession, it can be assumed that the relative importance of rock glaciers will increase in the Cordillera Real and Sajama. Climate modelling of the the 0 °C isotherm as a proxy for permafrost extent also highlighted this projected decrease. The projected impact of this warming on permafrost extent is modelled to be a loss of up to 95% by 2050 and 99% by 2080 from present day extent. These results were disseminated back to residents of La Paz through a conference held in the third field season (2014). This research is valued as important as continued climate change and population growth are projected to reduce water security in arid regions of the South American Andes. Due to its elevation and high levels of poverty Bolivia is vulnerable to climate change with limited ability to adapt. Specifically for the city of La Paz, its heavy dependence on the glaciers of mountains for potable water supply leaves it particularly vulnerable, especially during the dry season.NERC CASE studentship with Oxfam and Agua Sustentabl

Future climate warming and changes to mountain permafrost in the Bolivian Andes

Water resources in many of the world’s arid mountain ranges are threatened by climate change, and in parts of the South American Andes this is exacerbated by glacier recession and population growth. Alternative sources of water, such as more resilient permafrost features (e.g. rock glaciers), are expected to become increasingly important as current warming continues. Assessments of current and future permafrost extent under climate change are not available for the Southern Hemisphere, yet are required to inform decision making over future water supply and climate change adaptation strategies. Here, downscaled model outputs were used to calculate the projected changes in permafrost extent for a first-order assessment of an example region, the Bolivian Andes. Using the 0 °C mean annual air temperature as a proxy for permafrost extent, these projections show that permafrost areas will shrink from present day extent by up to 95 % under warming projected for the 2050s and by 99 % for the 2080s (under the IPCC A1B scenario, given equilibrium conditions). Using active rock glaciers as a proxy for the lower limit of permafrost extent, we also estimate that projected temperature changes would drive a near total loss of currently active rock glaciers in this region by the end of the century. In conjunction with glacier recession, a loss of permafrost extent of this magnitude represents a water security problem for the latter part of the 21st century, and it is likely that this will have negative effects on one of South America’s fastest growing cities (La Paz), with similar implications for other arid mountain regions

Hydrological modelling as a tool for interdisciplinary workshops on future drought

© 2018, © The Author(s) 2018. Transformative interdisciplinary methods and tools are required to address crucial water-related challenges facing societies in the current era of the Anthropocene. In a community-based study in the Limpopo basin of South Africa, physical and social science methods were brought together to run interdisciplinary workshops aimed at enhancing preparedness for possible future drought. To generate storylines for the workshops, relevant scenarios were modelled using a catchment-scale hydrological model, SHETRAN. Set up using freely available data, local knowledge, and narrative-based group interviews on past experiences of drought, the model acted as a locally-relevant tool for prompting discussions about potential future drought impacts, responses and preparedness, and to stimulate the production of community future narratives. In this paper, we discuss the elements involved in the modelling process: the building of the model through an interdisciplinary approach; setting up the model with limited data; and the translation of the model results into storylines for the workshops. We found that by using this methodology scientific grounding was given to the workshop storylines, and that the local context of the model and the engaging approach of creating narratives encouraged participant involvement in discussions about the future. The method of generating these future stories was an important process for the participants in developing their thinking about possible futures, preparedness and adaptation. In this paper we show how this alternative approach of using a hydrological model has benefits and we discuss the limitations and lessons of the approach for future interdisciplinary research

Anthropogenic activities alter drought termination

Despite the increasing influence of human activities on water resources in our current Anthropocene era, the impacts of these activities on the duration, rate and timing of the recovery of drought events, known as the drought termination phase, remain unknown. Here, we present the first assessment of how different human activities (i.e. water abstractions, reservoirs, water transfers) affect drought termination. Six case studies in Europe were used to analyse the human influence on streamflow drought termination characteristics. For all case studies, we compared the drought and drought termination characteristics derived from a human-influenced time series of streamflow (observation data) and a naturalised time series (modelled data) for the same period. Overall, results clearly demonstrate the influence of human activities on drought terminations in all the studied catchments. Groundwater abstractions, reservoirs and mixed influences were all found to increase the average duration of drought termination, whereas water transfers into the catchment decreased drought termination duration. Results also show that average drought termination rates increased in all case studies due to the human influence. Furthermore, start and end months of the termination phase were more skewed to certain months in human-influenced data than in the naturalised situation. Future research could extend this new knowledge by looking to add further case studies and covering different human activities to gain a wider understanding on how human actions modify hydrological droughts and their recovery. Furthering this work could also help to improve the forecasting of drought recovery in the Anthropocene, which is important for informing drought management decisions