Reference flows are important variables for assessing water availability in Brazil, as well as in rural communities in the state of Goiás (Brazil). However, as there is a lack of flowrate data and measurement points, regionalization methods have been used for forecasting the minimum reference flow (Qref) allowed for maintaining water uses. The present research covered 92 hydrographic basins within 46 selected rural communities in the state of Goiás, and 21 basins were selected for carrying out on-site flow measurements, as well as for Qref estimation following three regionalization methodologies. Results show a large variation between the values measured and estimated by the three methodologies, but the statistical analysis found regression equations of one of the methods more suitable for application in rural hydrograph basins of Goiás.

Hydrological information is essential for adequate water resources management as well as for water supply, energy supply, water allocation, among other services. However, this information does not always exist in quantity and quality to be used in hydrological or water management studies, and alternative methods are required to estimate minimum flows. Estimation based on homogeneous regions enables to transfer observation data from a known location to a location without data, but in the same region. Since the fluviometric stations in the state of Goiás (Brazil) are not uniformly distributed, the present work aimed at delimiting homogeneous regions of minimum flows, using the cluster grouping method with the K-means algorithm.Thus, 71 fluviometric stations with at least 5 years of continuous data were selected, obtained from the HIDROWEB system. In addition to the observed data, other variables were considered, such as drainage area, perimeter, specific minimum flows Q7,10, Q90, Q95 and average slope. The use of all these variables together with the observed data made it possible to determine,with great accuracy, 5 homogeneous regions of minimum flows based on the cluster analysis, enabling to obtain the minimum flows of reference for each region.In the selected homogeneous regions, it was possible to observe that the regions with the highest values of average slope presented smaller minimum flows, and the same could be observed under inverse conditions, i.e., lower values of average slope had higher minimum flows.It is also noteworthy that river monitoring is deficient in the center-south and center-north parts of the state of Goiás, making water resources management difficult. This fact indicates, therefore, the need to expand the river monitoring system throughout the state, especially in its southern and northern regions.

AbstractThe preferred data for analyzing water availability are those of historical flow series of the sources of interest; however, most Brazilian watersheds do not have sufficient fluviometric monitoring. Such cases require techniques for transposing data from one region to another, otherwise known as ‘flow regionalization’. The present work aimed to compare the method proposed by Secretaria de Meio Ambiente e Desenvolvimento Sustentável (SEMAD) of the state of Goiás with the traditional method of regionalization for determining reference flow at the mouth of the surface catchment basin of the Meia Ponte river. Data from eight fluviometric stations were used for regionalization, with the regression equations being adjusted using four different models. The result revealed that the potential and linear models performed the best, both with R2 and R2a values of 0.996 and 0.995, respectively. The relative error in the application of the potential model and of the method adopted by SEMAD were below 30%. The reference flows obtained by the two best performing methods differed, with flow determined by the traditional method being 5.93% lower than that of the SEMAD equation. Therefore, a more detailed study is recommended to determine which equation models better fit the region.