Soil moisture monitoring in the coarse active layer of a rock glacier (Central Andes, Argentina)

DARIO TROMBOTTO LIAUDAT; CARLA TAPIA BALDIS; MENDOZA MARTÍN

Delhi

Congreso; 36the International Geological Congress; 2020

Physical properties play a critical role in the seasonal or perennially frozen soils, controlling processes such as water storage and its exchange between different soil layers; thermal characteristics, heat transfer processes; kinematic responses, and mechanical behavior. Soil moisture is considered one of the essential climate variables to be monitored according to international scientific communities. Nevertheless, soil moisture observations are still unknown in the high-elevation mountains of the Central Andes. About that logistic difficulties play also an important role at the time of monitoring-site settlings. Since March 2018, coarse/blocky soils in the active layer of Candidato rock glacier are being monitored (31.9°S; 70.18°W). Three trenches above 4000 m asl and depth down to 90 cm were instrumented with sensors SMT100 and iButtons DS1922L to calculate soil temperature and volumetric water content. Soil granulometry, density, porosity, moisture and water saturation, thermal conductivities, thermal diffusivity, heat capacity, and latent heat were calculated in the laboratory from soil samples taken at different depths. The winters of the years 2018 and 2019 were very dry. According to our records, the uppermost levels of the active layer reached up to 40% of volumetric water content after each snow precipitation, followed by a quickly dried up from the surface to depth. From January to July, the same soil layers remained mainly dry. The open structure of the coarse/blocky soil layers controls not only the water residence times in the ground but also the heat transport transfer mechanisms.