Abstract
Water resources in high mountains play a fundamental role for societies and ecosystems in the regions and downstream areas that might be critically impacted by climate change and socio-economic factors in the future. The mountain cryosphere is one of the systems that is most affected by climate change. Glacier shrinkage leads to cascading impacts on downstream systems and profoundly influences the natural environment. This results in major changes for river flow regimes with altered provision of water resources to downstream populations, economic changes, shifts in occurrence and severity of natural hazards, as well as cultural changes associated with landscape character, identity, and spirituality. The Tropical Andes’ climate is characterized by a pronounced 7-8 months long wet season (austral summer) that alternates with a 4-5 months long dry season (austral winter). During the dry season almost no rainfall can be recorded. This interchanging pattern means that during the dry season water resources are primary supported by groundwater and melt water from glaciers. Water resources from glaciers are progressively affected by climate change and changing water demand. While climate change and glacier retreat already put great pressure on the water system, population growth, rising water usage of agriculture, changing lifestyles and water allocation rights exacerbate the problem leading to seasonal water scarcity during the dry months. Water scarcity is one major water risk connected to climate change and resulting glacier retreat. Glacial hazards such as outburst floods are also an ever-looming risk that is also increasing as lakes grow in size and different societal factors increase vulnerability. Different water related risks such as water scarcity and lake outburst floods are typically treated in a separate way. However, in a local context such as in mountain regions different water risks are intertwined and shaped by multi-dimensional natural and socio-economic drivers. Comprehensive analyses of risks related to water resources across different scales are complex and often missing in climate sensitive mountain regions where data scarcity represents important limitations. We address this challenge by assessing the interaction of these water risks within the high mountain glacierized setting of the Peruvian Andes. Within this study we leverage interdisciplinary methods to assess the current and future water risks in data-scarce mountain regions. Literature review, interviews and cross-impact-balance analysis were used to assess associated human impacts. Glacial II lake outburst flood modelling and a variation of a hazard matrix was used to analyze the risk associated with the floods. Finally, hydrologic modelling was used to examine the impact of diminishing glacier meltwater resources, with the addition of an integrated water model that links human-natural systems with future scenarios. We argue that specific impacts of climate change so far are insufficiently considered. Little is known about the associated combined processes and the interplay of multiple climatic and non-climatic stressors. Continued glacier lake formation and growth will likely result in a growing number of risks due to both population increase and societal dynamics, such as urbanization or settling in hazard zones. The effects of climate change on the natural system seem to be stronger than socio-economic. Nevertheless, a pronounced seasonal water scarcity is likely to occur in the near future, where socio-economic factors exacerbate the limiting water availability. Our study reveals how glacier retreat is rooted in numerous different cumulative negative impacts, which have implications for losses and damages mainly at the local level that can already be observed. The combination of qualitative and quantitative data revealed insights in the effects of climate change on water risks. We identify major implications such as the number of people affected by glacial hazards, future water availability, monetized agricultural crop loss due to loss of water, as well as non-economic values local people attribute to glacier loss. While we find that different emission and warming scenarios have important negative but differentiated effects on different natural and human systems we also contend that socio-economic factors have a great impact on already diminishing water resources. Especially under a high-emission RCP8.5 scenario when most low-lying glaciers could be gone, effects will be felt more strongly and future dry season water availability is critical to satisfy sectoral water demand. The combination of different water risks makes comprehensive risk management more complex and challenging. Globally oriented frameworks might not be easily applicable. In order to avoid pronounced water scarcity and glacier lake outburst risks, socio-economic variables have to be adapted and solutions for water buffers during the dry season are necessary. Policy needs to act to avoid worst-case scenarios.
Motschmann, Alina