Otimização do aproveitamento hídrico superficial na bacia hidrográfica do rio Araguari, Triângulo Mineiro

Abstract

The management of water resources provides a better use, control and conservation of water, however, the complexity of this planning is to attend multiple uses in an integrated and optimized way for the entire system. In order for the sustainability of the system to be efficient, the allocation of water availability among its multiple uses must be made in conciliation with environmental issues. The optimization of a water resources system is a complex engineering problem, requiring a mathematical formulation, coupled with computational algorithms, to be able to describe its natural dynamics. This is an area in development, but it already presents tools capable of generating solutions applicable to reality, among them the OPTIGES module linked to the AQUATOOL Decision Support System. In this context, through the OPTIGES module, this study sought to optimize the surface water utilization in the Araguari river basin, which is composed of several rivers and cascade hydroelectric reservoirs, in addition to a series of consumptive grants. Methodologies and criteria used to estimate the reference flow (Q7,10), basis for granting processes, were evaluated. In order to calculate the Q7,10 flow rate, the methodology provided by Atlas Digital das Águas de Minas was used, and a comparison was made with the values obtained by the Weibull probability distribution method. The relative differences found among these methodologies were significant, where, in 75% of the stretches analyzed along the basin, this value was higher than 10%, reaching a maximum of 161%. The results showed that, depending on the method used, the potential for water utilization may be limited, as well as ecosystems that depend on the minimum residual flow (50% of Q7,10) may be threatened. Regarding the study of optimization of the water use along the basin, seasonal criteria were evaluated for the estimation of flow Q7,10 against the current criterion (50% of annual Q7,10). By adopting two seasons throughout the year (rainy and dry), the results showed an increase in the available flow considering the seasonality of fluviometric regimes, where, for the rainy season, Q7,10 values were on average 47% higher than those obtained by the annual criterion, and for the dry period, on average 10% higher. An analysis of the maximum percentage of Q7,10 to be granted was also carried out, aiming to indicate which percentage would represent a greater efficiency in the optimization of the water use. The results showed that the transition from 50% to 70% of Q7,10 as a concession criterion had the greatest impact on increasing water availability and conflict resolution. Regarding the critical areas with conflicts between demands, rationing was necessary in drought periods so that the volume granted did not reach the residual minimum flow rate of 50% of Q7,10. The maximum values of cuts in the obtained volume reached 55%. Despite this, the general situation in the river basin and the availability of water resources is comfortable, especially close to the main rivers, where the volume granted does not reach 30% of the allowed, and next to the four large reservoirs (Nova Ponte, Miranda, Capim Branco 1 and Capim Branco 2) of the Araguari river, where the potential still exists for captation is favorable, with capacity to supply cities of the size of Uberlândia.