Evidence of water surface and flow reduction in the main hydrographic basin of the Brazilian savannah (Cerrado biome): the Araguaia river

Reconciling environmental conservation with growing demands for food, water, and energy is a global challenge. Brazil, a major agricultural producer, grapples with deforestation's environmental costs. The Araguaia River basin, vital for Brazil's economic growth, undergoes significant land use changes. Assessing data from 1987 to 2019, we studied annual water surface variations, considering deforestation, agriculture, livestock farming land, and central pivot irrigation, and historical water flow series from 1980 to 2020 from 21 monitoring stations. We observed notable reductions in flooded areas (angular coefficients from 130 a 2,276 ha/year) and water flow the entire basin (b = - 13.84; t = - 4.8; P < 0.001) and its regions (Upper Araguaia: b = - 3.32; t = - 4.5; P < 0.001; Middle Araguaia: b = - 8.70; t = - 4.8; P < 0.001; Lower Araguaia: b = - 45.49, t = - 4.7; P < 0.001) over recent years. Water flow reductions persist year-round, with a marked decrease during low water periods (F-3,F-8 = 8.82; P = 0,006), aligning with heightened water demand for intensive agriculture. Tributaries and the main channel show similar reduction processes (t = 0.16; g.l. = 19; P = 0.873). Ensuring the basin's ecological flow is imperative for the aquatic ecosystem's minimum requirements.