The Andes Cordillera. Part II: Rio Olivares Basin snow conditions (1979–2014), central Chile

ABSTRACT Snow cover extent, duration, and properties were simulated (1979/1980–2013/2014) for the Rio Olivares Basin (548 km2) in central Chilean Andes, in an effort to understand conditions and trends (linear) at a basin scale. The National Aeronautics and Space Administration Modern‐Era Retrospective Analysis for Research and Applications products, together with the snow modelling software package SnowModel allowed simulations of first‐order atmospheric forcings (mean annual air temperature (MAAT) and water‐equivalent precipitation) and terrestrial snow features (snow cover extent, duration, snow water‐equivalent depth, snow density, and runoff generated from snow melt). Simulated snow cover extent and depletion curves were verified against Moderate Resolution Imaging Spectroradiometer‐derived snow cover data. For the Rio Olivares Basin, MAAT was −2.9 ± 0.6 °C with a mean 0° isotherm at 3325 m a.s.l. The greatest temporal and spatial changes in temperature over the 35‐year period occurred in January and at the highest elevations, respectively. Mean annual precipitation was 1.86 ± 0.60 m w.e., indicating an increase in precipitation of ∼0.1 m w.e. 100 m−1 increase in elevation. On average, ∼90% of the basin precipitation fell as snow, varying from 70% at ∼2600 m a.s.l., to 95% at ∼4200 m a.s.l. In 20 out of 35 years the snow cover extent went to 0% (no basin snow cover) by end‐of‐summer (during March), and the snow duration increased on average by ∼10 days 100 m−1 increase in elevation. Approximately 85% of the basin outlet freshwater runoff originated from snowmelt, making snowmelt a dominant contributor to water resources. Snowmelt‐derived basin runoff was dominated by variability in snow precipitation rather than by variability in MAAT.