QUANTITATIVE AND QUALITATIVE ANALIZE OF WATER ALLOCATION IN RESERVOIRS OF SEMIARID REGIONS
Water availability. Granting. Reservoirs. Semiarid.
Over the past years the Brazilian semiarid region has been experiencing one of the worst scenarios in terms of water availability. In addition to the reduction in quantitative terms, it has been verified that most of the reservoirs are eutrophic which can compromise the available flows to meet the demands. This has resulted in increased conflicts over water uses requiring increasingly efficient reservoir operations. Thus, this research aims to propose a simplified methodology for the allocation of water in semi-arid region reservoirs, considering the quantitative and qualitative aspects of water resources, so that it is possible to verify the maximum water availability that can be granted without compromising sustainability of the reservoirs. The proposed methodology was based on simulation and optimization techniques using total phosphorus as the quality parameter. The relationship between the quantitative (percentage of stored volume) and qualitative (total phosphorus concentration) aspects of water resources was obtained through linear regression. The result of the statistical analysis showed that the percentage of the stored volume is a potential indicator to estimate the concentrations of total phosphorus present in the reservoirs which validates the proposed methodology. This methodology was applied to four different scenarios and the results showed that even without considering the qualitative aspect of water resources in the water allocation process most of the reservoirs in the semi-arid region are not able to meet the required demand. Inserting the qualitative aspect of the water resources in the proposed methodology and limiting the maximum concentration of total phosphorus present in the waters of the reservoirs as established by CONAMA Resolution 357/2005, it was observed that the water availability of the analyzed reservoirs was reduced by 100% when considered the reservoir as a freshwater body Class 2 and 60% when considering the reservoir as a freshwater body Class 3, evidencing the poor water quality of the analyzed reservoirs and the qualitative aspect may compromise the water allocation process.