Minimum flow and water availability in the baixo Paraiba do Sul watershed, Brazil: impacts of climate change and demand trends

Abstract

The Paraíba do Sul River watershed in Rio de Janeiro, Brazil, has experienced significant changes in precipitation patterns and flow regimes due to climate change and anthropogenic pressures, such as water transpositions and hydropower reservoirs. This study aimed to assess water availability trends, focusing on minimum flows in the Baixo Paraíba do Sul region and its key tributaries: Pomba, Muriaé, and Dois Rios. Using a statistical approach, historical flow data from 2012 to 2022 were analyzed, including the severe 2014-2015 drought. The methodology involved exceedance probabilities (Q95) and frequency analysis to evaluate monthly flow variability. Results showed considerable reductions in Q95 flows: 30.9% in the main Paraíba do Sul channel, 35.9% in Dois Rios, 42.4% in Muriaé, and 46.3% in Pomba. Additionally, monthly flows fell below residual levels in 22%, 19.7%, 18.9%, and 11.4% of cases for these regions, respectively. These findings highlight the urgent need to revise the watershed management plan to address current water demands and adapt to climatic changes effectively.