Resumo:
Monitoring streamflow is essential for assessing the volume of water available in a watershed and identifying variations in this variable. This is crucial for effective water resource management and decision-making regarding water use. This study aimed to analyze the trends in historical data from the Piracicaba River basin from 1987 to 2022 and investigate their possible causes. For annual precipitation, no statistically significant trends were detected. In contrast, the estimated annual potential evapotranspiration for the Piracicaba River basin showed a significant increasing trend (p = 0.0002). A reduction in streamflow was identified starting in 2010, with statistical significance in three out of the four stations analyzed (p = 0.0301*, 0.0234*, 0.177, and 0.0835*). Regarding land-use changes over the years, a 6.6% reduction in agricultural land and a 33% increase in urbanized areas were observed. Notably, the mining area increased by 130%. This significant increase in mining areas may be related to the decline in streamflow in the Piracicaba River since 2010, due to intensified exploitation of water resources. The elasticity analysis of the historical series indicated that a 10% increase in potential evapotranspiration reduces streamflow by 39.5%, while a 10% reduction in precipitation reduces streamflow by about 16.5%. The trend magnitude analysis revealed a loss of 1.8 mm/year at the Carrapato Brumal station and 1.75 mm/year at the Rio Piracicaba station. The MC station (magnitude of -4.51) also shows a sharp decline, but with marginal significance, i.e., nearly significant. These results highlight the importance of continuous streamflow monitoring and integrated water resource management, especially in the context of climate change. The intensification of mining and the increase in potential evapotranspiration call for adaptation and mitigation measures to ensure water sustainability in the Piracicaba River basin.
