Where Does the Chilean Aconcagua River Come from? Use of Natural Tracers for Water Genesis Characterization in Glacial and Periglacial Environments

Abstract

The Aconcagua river basin (Chile, 32 °S) has suffered the effects of the megadrought over the last decade. The severe snowfall deficiency drastically modified the water supply to the catchment headwaters. Despite the recognized snowmelt contribution to the basin, an unknown streamflow buffering effect is produced by glacial, periglacial and groundwater inputs, especially in dry periods. Hence, each type of water source was characterized and quantified for each season, through the combination of stable isotope and ionic analyses as natural water tracers. The δ18O and electric conductivity were identified as the key parameters for the differentiation of each water source. The use of these parameters in the stable isotope mixing “simmr” model revealed that snowmelt input accounted 52% in spring and only 22–36% during the rest of the year in the headwaters. While glacial supply contributed up to 34%, both groundwater and periglacial exhibited a remarkable contribution around 20% with some seasonal variations. Downstream, glacial contribution averaged 15–20%, groundwater seasonally increased up to 46%, and periglacial input was surprisingly high (i.e., 14–21%). The different water sources contribution quantification over time for the Aconcagua River reported in this work provides key information for water security in this territory.

Influence of Intensive Agriculture on Benthic Macroinvertebrate Assemblages and Water Quality in the Aconcagua River Basin (Central Chile)

“…The Aconcagua River Basin decreased its flow in recent years, being declared to have water scarcity by the Chilean government [51]. The dramatic decrease in river flow is associated with climate change and activities related to agriculture, such as excessive water diversions for irrigation canals in the middle and lower part of the basin, which implies a decrease in the main river flow and consequent increase in its temperature.…”

A conceptual hydrological model of semiarid Andean headwater systems in Chile

“…Previously, using similar methods, Rodriguez et al (2016) found that a rock glacierized sub-basin of the Juncal River basin (∼33°S), contributed to 29% of total 2011–2012 summer discharge. Finally, at the same latitude, Crespo et al (2020b) studied the headwaters of Aconcagua River, observing a surprisingly high contributions from periglacial environment of 11–30%, depending on the season and the elevation, but higher during summer and autumn.…”

“…Likewise, Rodriguez et al (2016) and Crespo et al (2017) signaled the importance of subsurface storage in the high-elevation catchments of the Juncal and Mendoza rivers, respectively, reflecting a higher contribution during the autumn and winter seasons. More recently, Crespo et al (2020b) estimated an average groundwater contribution of 28% at the Aconcagua River headwaters, increasing with lower elevations and being relatively higher in wintertime (34%).…”

“…In this way, through the analysis of stable water isotope at Aconcagua River headwaters, Crespo et al (2020b) determined that recharge of water occurs at around 3700 m a.s.l. In the same basin, groundwater circulation in fractured rocks above 2000 m a.s.l.…”

Isotopic signature of a glacial influenced hydrological system in northern Patagonia, Argentina

“…According to these authors there appears to be a gap in isotope data of South American hydrological systems when compared to the rest of the world. In particular, in the Andes ranges, the application of water isotopes as natural tracers is mainly concentrated in the Central Dry Andes (Crespo et al, 2017; Crespo et al, 2020; Massone et al, 2016; Ohlanders et al, 2013; Sileo et al, 2020; Trombotto Liaudat et al, 2020). Thus, it is important to highlight that the data presented here represents the first isotopic data recorded in the Manso River basin.…”