Cryospheric headwater genesis discrimination and social perception under megadrought and climate change scenarios: the Putaendo Valley case, Chile

Sebastián Andrés Crespo^1*Justinne Rybertt Goldammer²Tomás Palmisano³Céline Lavergne⁴Andrés Lo Vecchio¹Luis Muñoz Gaete²Francisco Fernandoy²Yuliya Vystavna⁵

• ¹CONICET Argentine Institute of Nivology, Glaciology and Environmental Sciences (IANIGLA), Mendoza, Argentina
• ²Laboratorio de Análisis Isotópico (LAI), Facultad de Ingeniería, Universidad Andrés Bello, Viña del Mar, Chile
• ³Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) / Instituto de Investigaciones Gino Germani, Universidad de Buenos Aires, Buenos Aires, Argentina
• ⁴Departamento de Ciencias Geográficas, Facultad de Ciencias Naturales y Exactas, Universidad de Playa Ancha, Valparaiso, Chile
• ⁵Isotope Hydrology Section, International Atomic Energy Agency, Vienna, Vienna, Austria

The Putaendo watershed (Central Andes, Chile), significant for its pre-colonial history and as a first independent Chilean town (1817), also exhibits special hydrological features. It is one of the few examples in the Andes Cordillera where the inhabitants almost entirely rely on periglacial water sources. The region has also endured a severe mega-drought since 2010, drastically altering the water supply and strained the livelihoods of pastoralists and peasants to the limit. However, despite the deep decrease in precipitation recorded during the megadrought, the water continued flowing from the headwaters to the Putaendo River. To elucidate the mechanisms behind this water persistence, we quantified the individual contributions of different water sources (snow, rock glaciers, and groundwater) within this basin through the analysis of stable water isotopes and major ions. The region's simple winter precipitation regime, another crucial hydrological characteristic, further facilitate the clear discrimination and quantification of meltwater inputs distinct from precipitation using physicochemical tracers. Additionally, to comprehensively understand public knowledge regarding water origin, the impact of the megadrought and climate change, and potential mega-mining projects (as the last basin without this activity in the Chilean Central Andes), we conducted a social perception analysis using a cross-sectional descriptive survey with non-probabilistic causal sampling. Upstream of the Chacrillas dam's human intervention, the river in this arid water cycle exhibited a marked predominance of water contribution from rock glaciers (56.1%), followed by groundwater (32.7%) and snow (11.2%). The inhabitants of the territory displayed a remarkable awareness and prior knowledge that was manifested when 45.5% of the respondents referred to rock glaciers as the main contributor of water during dry years. There was also a clear negative public opinion regarding the developing of mega-mining projects in the valley (84.1%). Integrating these perceptions of water scarcity's social complexities with the advanced understanding of water source contribution yields crucial information for regional water security management.