Snow and Glacier Contributions to the Mendoza River in the Semiarid Central Andes of Argentina

The ongoing and persistent drought in Central-western Argentina since 2010 has led to a water crisis in the region. Despite the crucial importance of the Andean water resources for natural ecosystems and socio-economic activities, few studies have focused on understanding snow and ice contributions to surface runoff dynamics during dry, normal and wet years in main regional watersheds like the Mendoza River, which is the main water supply for the most extensive and densely populated irrigated oasis in central-western Argentina. To better understand snow and glacier temporal storage-and-release processes and their impact on the seasonal and inter-annual variability of the Mendoza River, we provide up-to-date modelling work using the numerical model HBV.IANIGLA, which specifically incorporates separate snow and glacier components into the hydrological simulations. Modelled snow accumulation values show that the lower eastern sectors of the Mendoza watershed usually receive five times less snow than the westernmost areas bordering Chile. When comparing our results with other modelling outputs from the adjacent Maipo and Aconcagua watersheds in Chile, we find that these western basins accumulate nearly 3.5 times more snow, corroborating the marked west–east precipitation gradient in the region. During the last 40 years, snow has been the main source of meltwater for the Mendoza River, but glaciers have contributed, on average, ~18% of the annual discharges. Maximum values that exceed 40% in glacier contribution were modelled in years with very low winter snow accumulation. This is, particularly, evident during the extended dry period that started in 2010, when the glacier contribution averaged ~30% compared to ~15% before that period. These very dry years usually concentrate the bulk of the annual discharges later than normal years during the warm melting season. These results provide an improved understanding of the surface water variability in this semiarid region for the last 40 years.