SWOT enables the regional quantification of a record water stock fluctuation in the shallow lakes of the Pampas following a multi-year drought

In flat sedimentary landscapes, shallow lakes and ponds (hereafter, SLPs) are a highly dynamic component that provides habitat for local and migratory fauna, water resources for surrounding vegetation and livestock, as well as regulation of local climate and biogeochemical fluxes. In the Pampas of central Argentina, SLPs are highly sensitive to precipitation and evapotranspiration fluctuations, displaying strong multi-year (rather than seasonal) expansion-recession cycles. Here, with the aid of SWOT data, we report for the first time the volume stored by these SLPs, leveraging recent historical records of their recession minimum (early 2023) and subsequent expansion rate (2023-2025) and maximum (late 2025). This hydroclimatic turnover in concurrence with the deployment of the satellite mission provides a unique opportunity to study local to regional changes in water surface elevation, area, and inferred volumetric changes in small and temporary water bodies. 
We focus our study on the “Pampa Interior Plana” subregion, with 85,000 km2 and regional slopes < 0.01%, hosting > 50,000 SLPs of a median area of 1.3 ha that cover 10% of the region on the long-term average. We tracked the five highest rainfall events between October 2023 and December 2025 (40-130 mm), and corresponding Lake-SP-derived water surface elevation and area changes at regional (> 7,000 water bodies) and local (ten SLPs ranging 0.5-2000 ha) scales.
Preliminary results indicate directional increases in elevation over the whole region of up to 3 meters between the driest state and the maxima observed in 2025, which translates into more than 5 billion cubic meters of stored water. When comparing individual SLP responses to a gradient of rainfall intensity, a marked heterogeneity can be observed, with some systems exhibiting rapid surface elevation and area increases, others showing less-sensitive variations in elevation. This variability suggests either (a) the strong modulation by antecedent conditions in soil moisture and water table level, (b) morphometric differences between these shallow water bodies dictating e.g., predominantly lateral vs. combined lateral and vertical expansion, or (c) difficult to isolate, evaporative forcings between successive SWOT observations. Importantly, this work illustrates the insights that SWOT enables into the hydrological functioning of extensive lowland freshwater systems.