Drought-induced soil moisture declines in Andean catchments inferred from satellite-derived ground displacement

Abstract

The 2023–2024 drought reduced water availability worldwide, yet its impacts on soil moisture remain unknown in ungauged Andean catchments. Therefore, we assessed drought-induced soil moisture changes across seven catchments in Ecuador using a multivariable approach that integrates Sentinel-1 A SAR interferometry (InSAR)-derived vertical ground displacement as a relative indicator for soil moisture, soil moisture anomalies, ERA5 precipitation, and land cover data. Ground subsidence indicated a progressive decline in soil moisture. The magnitude of decline varied with elevation and land cover, with the lowest impacts in the uplands (4000–4400 m a.s.l) covered by páramo vegetation (tussock grass and cushion plants) and the strongest impacts in the lowlands (≤ 3400 m a.s.l) covered by grazing pastures. These patterns reflect climatic and hydrologic gradients, better-preserved upland soils and vegetation, soil degradation, and lower water-use efficiency in lowland pastures. InSAR has potential to monitor soil moisture during hydrological drought in the Andean data-scarce catchments, and reveal contrasting drought resilience among land covers, which provide evidence towards improved natural resources management.