Hydroclimatic Trends, Streamflow Variability, and Land-Use Change in the Ribeira de Iguape River Basin, Brazil

Hydroclimatic variability and land-use and land-cover (LULC) change were investigated in the Ribeira de Iguape River Basin, Brazil, using precipitation records from 14 gauges and mean, maximum and minimum streamflow from 10 stations within 1960–2024, alongside annual LULC maps for 1985–2024. Hamed–Rao Mann–Kendall tests, Sen’s slopes and change-point analyses were complemented by temporal-dependence, interstation-consistency and false-discovery-rate diagnostics. After adjustment, seven precipitation stations exhibited increasing annual trends and one showed a decrease. The largest positive slopes occurred at Balsa do Cerro Azul (+101.5 mm decade−1), Guanhanha (+98.3 mm decade−1) and Capela da Ribeira (+90.1 mm decade−1). However, pronounced departures from regional reference series around 1981 at two neighbouring gauges preclude an unequivocal climatic interpretation. Streamflow responses were more localised. Declining maximum discharge at Juquiá (−16.2 m3 s−1 decade−1) was the only annual streamflow trend retained after adjustment, without a comparable downstream decline over common years. Urban and mining areas expanded, whereas forest cover initially declined and subsequently recovered partially, remaining below its 1985 extent. Land-cover proportions extracted within ten independently DEM-delineated upstream catchments yielded 228 estimable contemporaneous LULC–discharge correlations. Although 21 were nominally significant, none remained significant after Benjamini–Hochberg adjustment within the corresponding discharge-metric families or across the pooled set. These findings reveal spatially differentiated hydroclimatic and landscape trajectories, without establishing a causal contribution of LULC change to observed streamflow variability.