Interplay of climate change and human activities on the hydrological dynamics and environmental degradation of the Senguerr River Basin, Argentina

Abstract

This study examines the multi-annual evolution of the Senguerr River Basin in central Patagonia (Argentina), focusing on fluvial dynamics and long-term hydrological changes. The analysis of climatic and hydrological data since 1950 identified eight distinct hydrological stages, with runoff trends strongly correlated to ENSO phases. During the La Niña phases, discharge in downstream areas decreases by 33–36 % compared to the El Niño phases. Gradual increases in average temperatures and decreased winter precipitations lead to pronounced water deficits in summer, with changes in the snow-to-rain ratio. Hydrograph analysis in the basin's headwaters reveals three major periods: (i) 1950–1976, characterized by two flood peaks—one from winter precipitation, another from spring snowmelt; (ii) 1978–2000, marked by reduced discharge and smoother hydrographs; and (iii) 2001–2024, showing erratic precipitation and sharp-peaked hydrographs, indicative of a rain-dominated catchment. In recent decades and due to climate warming, the Lower Basin faces a seasonal hydrological deficit, with an annual precipitation of 154 mm and evaporation of 1738 mm. However, despite a 2.18 °C temperature increase (1989–2015), reduced summer wind velocity, likely due to a southward shift of the westerlies, has mitigated evaporation rates. Agricultural water use in the Upper Basin and Sarmiento Delta surpasses urban consumption by over 900 %, with irrigation in the Upper Basin using three times the combined domestic and industrial water supply and 6.23 times more in the Lower Basin. The desiccation of Colhué Huapi Lake is driven by reduced discharge through the Falso Senguerr course and increasing La Niña frequency, exacerbated by higher water consumption in the Lower Basin. These processes have intensified desertification, favoring the formation and migration of eolian dunes on the dry substrate and increasing dust transport during windstorms.