Glacier runoff variations since 1955 in the Maipo River basin, in the semiarid Andes of central Chile

Abstract

Abstract. As glaciers adjust their size in response to climate variations, long-term changes in meltwater production can be expected, affecting the local availability of water resources. We investigate glacier runoff in the period 1955–2016 in the Maipo River basin (4843 km2, 33.0–34.3∘ S, 69.8–70.5∘ W), in the semiarid Andes of Chile. The basin contains more than 800 glaciers, which cover 378 km2 in total (inventoried in 2000). We model the mass balance and runoff contribution of 26 glaciers with the physically oriented and fully distributed TOPKAPI (Topographic Kinematic Approximation and Integration)-ETH glacio-hydrological model and extrapolate the results to the entire basin. TOPKAPI-ETH is run at a daily time step using several glaciological and meteorological datasets, and its results are evaluated against streamflow records, remotely sensed snow cover, and geodetic mass balances for the periods 1955–2000 and 2000–2013. Results show that in 1955–2016 glacier mass balance had a general decreasing trend as a basin average but also had differences between the main sub-catchments. Glacier volume decreased by one-fifth (from 18.6±4.5 to 14.9±2.9 km3). Runoff from the initially glacierized areas was 177±25 mm yr−1 (16±7 % of the total contributions to the basin), but it shows a decreasing sequence of maxima, which can be linked to the interplay between a decrease in precipitation since the 1980s and the reduction of ice melt. Glaciers in the Maipo River basin will continue retreating because they are not in equilibrium with the current climate. In a hypothetical constant climate scenario, glacier volume would reduce to 81±38 % of the year 2000 volume, and glacier runoff would be 78±30 % of the 1955–2016 average. This would considerably decrease the drought mitigation capacity of the basin.

A near 90-year record of the evolution of El Morado Glacier and its proglacial lake, Central Chilean Andes

“…Although the glacier contribution to runoff at basin scales in the Central Andes is minor compared to other components (snow, rainfall) (Masiokas and others, 2006;Ayala and others, 2020), previous hydrological studies have highlighted the importance of glacier contributions in the Maipo River basin during dry periods. During the severe drought of 1969, one of the driest summers on the hydro-meteorological record, about 67% of the total runoff at the outlet of the basin was originated from glacier meltwater (Peña and Nazarala, 1987).…”

“…In recent years, a large number of glaciological and climatological studies in the Central Andes have improved our knowledge of glacier-climate interactions in this region (e.g. Ragettli and others, 2013;Pellicciotti and others, 2014;Ayala and others, 2016;Masiokas and others, 2016;Bravo and others, 2017;Braun and others, 2019;Burger and others, 2019;others, 2019, 2020;Schaefer and others, 2020;Ayala and others, 2020). However, multi-temporal analyses of glacier fluctuations, in particular, have focused mainly on changes in glacier length and area (e.g.…”

Monitoring Spatial and Temporal Differences in Andean Snow Depth Derived From Satellite Tri-Stereo Photogrammetry

“…The recent, prolonged occurrence of drought for the central Chilean Andes is of serious concern for the future water security of the region (Meza et al, 2015;Garreaud et al, 2019). Ayala et al (2020) estimated that glacier contributions to streamflow of the Maipo River (1955-2099) may have already peaked if climate was to stabilize at the level of the past two decades. Such model findings of the last decades also support the large scale observed patterns in glacier mass balance related to the so-called "mega-drought" (Braun et al, 2019;Dussaillant et al, 2019;Farias-Barahona et al, 2019;Farias-Barahona et al, 2020a;Farias-Barahona et al, 2020b;Masiokas et al, 2020).…”

“…Nevertheless, the relative contributions of glaciers are governed by the hydrological snow year in the upper catchments of the central Andes, which are typically snow-dominated. For example, estimates of annual streamflow contribution from snowmelt for the Rio Yeso catchment are up to 97% for wet years (Burger et al, 2019) and estimated as 54 ± 10% on average for the entire Maipo catchment of 4,843 km 2 between 1955-2016 (Ayala et al, 2020).…”

“…The key challenge of all such modelling studies in mountainous regions to date, is the uncertainty in the distribution of solid precipitation in space and time (Ragettli et al, 2014;Ayala et al, 2016;Burger et al, 2019;Ayala et al, 2020;Shaw et al, 2020b), largely governed by the lack of high elevation data and/or the reliability of high elevation snow-precipitation records (e.g., Scaff et al, 2018). Shaw et al (2020a) addressed this challenge by using Pléiades DEM differencing to obtain an estimate of snow depth for the Rio Yeso catchment.…”