Estimative of reference flows for water resources planning and control: hydrologic regional indicators application

Due to limitations of hydrometeorological monitoring network related to spatial station distribution and extension of historical series, tools that aim to improve consistency and optimize available data analysis have become essential. In this context, regionalization techniques stand out, once the main focus is the delimitation of hydrologically homogeneous regions with the subsequent spatial transposition of hydrological variables of interest. Regional indicators, defined as the mean values of hydrological variables and characteristics of a homogeneous region, constitute an expeditious approach to hydrological regionalization. The main perspective of the study was to evaluate the use of regional indicators when quantifying reference flows associated with average flow, drought, or flood conditions. The study area selected was the Manhuaçu River basin, a major Doce River tributary, located in the state of Minas Gerais, Brazil. The results showed that the regional indicators allow estimates of diverse reference flows with mean errors lower than 30%, considered satisfactory for the study area. However, the conventional method of flow regionalization presented more consistent results, with mean errors usually lower than 20%, regardless of the reference flow analyzed. It was also observed that adopting historical flow series with varied extensions did not produce relevant differences when appropriating the diverse reference flows for the Manhuaçu River basin, with none exceeding 3%.