HYDROLOGIC SIGNATURES ON LAGOON COMPLEX AND WETLAND INUNDATION IN THE LITHIUM TRIANGLE OF THE ALTIPLANO-PUNA REGION

Shallow surface water bodies (lagoons) and vegetated wetlands are critical for sustaining biodiversity in ecosystems associated with lithium brine-bearing aquifers. In the Altiplano-Puna region (the “Lithium Triangle”), lagoons form a critical habitat for flamingos and upgradient freshwater springs feed vegetated wetlands, which serve as an ideal growing environment for bofadeles. Yet hydrologic mechanisms controlling inundation are still poorly understood. Given that previous tritium-based analyses confirm that water sources to lagoons have a complex suite of ages, we further aim to establish the dependency of surface water dynamics on groundwater sources across the region. More than 36 years of Landsat observations provide a validated basis for assessing surface water and NDVI-identified vegetated wetlands through pre-development by using surface area variability as a proxy for resilience. Higher spatial and temporal resolution via synthetic aperture radar from the Sentinel-2 satellite extends analysis to attributing the hydrologic mechanisms that influence surface water inundation, namely response to precipitation and reliance on groundwater discharge. Landsat-based analysis supports that surface waters across the region share trends which indicate common dominant hydrologic mechanisms. These include controls on inflow, like spring discharge of groundwater sources versus precipitation sensitivity, and outflow, like discharge to downgradient surface waters versus evaporation. Despite evaporation-controlled seasonality, certain surface waters are resilient to drought. Persistence of vegetated wetlands upgradient to such surface waters further support the presence of groundwater discharge. Inundation variability beyond seasonality can be categorized by sensitivity to precipitation events based on Sentinel-derived surface water analysis, and by sensitivity to drought based on 5-year rolling window Mann Kendall trend analysis of the Landsat record. This work discretizes both the intra-annual and multi-decadal climatic responses of surface water for the region as well as the possible associated hydrologic mechanisms that dominate these trends. It also provides a framework for assessing surface water resilience in other arid basins and lithium-bearing aquifers.