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

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.