Estações pluviométricas da bacia hidrográfica do rio Araguaia: qualificação e modelagem de dados hidrológicos

Abstract

The Araguaia River basin, situated in a strategic transition zone between the Cerrado and the Amazon, plays a vital regulatory role in the environmental and economic stability of Central Brazil. However, the system faces unprecedented pressures due to the rapid expansion of the agricultural frontier, which has massively converted native vegetation into intensive land-use areas. This research aimed to qualify the historical data network and model the basin’s rainfall dynamics between 1975 and 2023, identifying long-term trends integrated with relief and land-use characteristics. The methodology was based on computational processing using the R language to execute automated algorithmic data cleaning routines, which allowed for the reduction of the initial inventory of 209 rain gauges to only 91 statistically suitable units, revealing a “data economy” that imposes critical monitoring gaps. Temporal analysis applied the Rainfall Anomaly Index and non-parametric tests, such as Mann-Kendall and Sen’s Slope Estimator, cross-referencing the results with digital elevation models and MapBiomas historical series. The results demonstrate a structural drying process in the basin with a rainfall reduction rate of -25.49 mm/year, with the year 2007 marking the definitive inflection point for an uninterrupted block of years classified as “Very Drey”. Spatially, a severe polarization was observed: headwaters and recharge zones in the Southern sector suffer from pronounced “top-drying” with the sharpest declines occurring on plateaus above 500 meters in altitude. The replacement of the Cerrado with pastures deactivated the “biotic pump” and removed the natural “hydraulic brake”, favoring violent surface runoff at the expense of deep infiltration. It is concluded that the recharge failure of the southern headwaters directly threatens the flood pulse of Bananal Island, evidencing the “death of stationarity” in regional water management. The current planning model creates an imminent risk of issuing “paper water entitlements”, necessitating an urgent transition to adaptive governance models and the rigorous protection of recharge areas on the plateaus.