Hydrological shifts in the Cerrado's largest free-flowing river under land use and climate pressure

Abstract

The Araguaia River is the longest free-flowing river in the Brazilian Cerrado, a biome characterized by pronounced seasonality, high biodiversity, and extensive agricultural development. The river supports floodplain systems, groundwater recharge, and multiple human uses, but has undergone rapid landscape transformation in recent decades. This study evaluates long-term trends in river discharge and assesses the relative influence of land use and climate variability from 1985 to 2022. We used in situ hydrometric data for minimum and maximum annual discharge, precipitation and climate indices, and annual land use and land cover data. The Mann-Kendall test and Sen's slope estimator were applied to detect trends, while Random Forest regression quantified the influence of land use and climate variables. Results show a consistent decline in both minimum and maximum annual discharge across most hydrometric stations. Land use change, particularly deforestation and agricultural expansion, was the primary driver of reduced minimum discharge. For maximum discharge, climate variables—including precipitation anomalies and El Niño/La Niña events—had greater relative influence, although land use effects remained significant. The expansion of irrigated areas further reduced baseflow, especially during the dry season. Variations in discharge trends across the basin corresponded to geomorphological differences, including floodplain extent and channel confinement. These results underscore the need for coordinated land and water management strategies in the Cerrado. Preserving native vegetation, regulating irrigation, and strengthening monitoring efforts are necessary to maintain the hydrological stability of the Araguaia River and ensure long-term water availability in one of South America's most dynamic agricultural regions.