SHRINKING OF GROUNDWATER-DEPENDENT LAGUNA SANTA ROSA WETLAND IN THE CHILEAN ALTIPLANO: A CRITICAL ASSESSMENT BASED ON REMOTE SENSING AND PIEZOMETRIC DATA

Wetlands are one of the most threatened ecosystems on the Earth, despite their great importance as an habitat for an enormous amount of species and corresponding to one of the most productive environments on the planet. Present work is the outcome of an investigation on Laguna Santa Rosa's (LSR) vulnerability resulting from ongoing metal mining operations in its surroundings that require a large volume of water extracted from local aquifers, in addition to a high evaporation rate in the area. This groundwater-dependent wetland will soon be further vulnerable with the commencement of water exhaustive lithium mining at Salar de Maricunga, with the extraction project already having environmental impact study approved. Sustainability of this wetland protected under the Ramsar convention and home to various wildlife species habiting this highland sector of the Andean Cordillera is vital for the associated groundwater-dependent ecosystem associated. A continuous decrease in the water level of LSR, a hypersaline lake at the southern extreme of Salar de Maricunga, a salt flat in the Atacama Region of Chile, was observed through the study of satellite images between 1993 and 2014, showing contraction of the water. However, this contraction trend was punctuated by extreme rainfall and consequent flood with accumulated precipitation exceeding 40 mm in a single day and hourly mean rainfall rates higher than 10 mm/hour at several locations in the hyperarid Atacama Desert on March 25, 2015. This raised the lake's water level, and thus the areal extent of the lake water observed in the satellite images of the period 2016-2017 following the extreme weather events of 2015. Another phase of high rainfall and flooding, although of lesser intensity than March 2015, occurred in the region in May 2017 and the most recent one of even lesser intensity in January 2019. During the twentieth and twenty-first centuries, over a dozen extreme weather events with high rainfall causing floods of varying intensity are also reported. Since the last two extreme weather events of 2017 and 2019 (similar to that of 2015 but not as severe) are likely to have disrupted the contraction trend of LSR, present study's time frame is 1993-2014. The registry for the 2016-2017 period accounts for the effect of extreme weather events of 2015 and 2017. The interplay of these extreme weather events and groundwater extraction for mining activities in the area makes the assessment of the affect of the latter complex, and limited to the intervals between successive extreme weather events.