Among all the basic needs for human survival it is possible to highlight the vital importance of water in all processes. Thus, assessment of water quality, not only, the amount of water is required and should be made based on studies to characterize the quality in order to define their application and even its reuse. Some of these studies are represented mathematically by a Water Quality Index (WQI) and the Trophic State Index (TSI) which can classify water reservoirs, for example, according to the incidence of eutrophication process. For this purpose, the literature contains several WQI's which can be applied, such as IQAR (IAP), O-IQA, IQA and PW-CPCB-IQA, as well as for the TSI proposed by Carlson. However, in these applications there is a need for obtaining many physicochemical and biological parameters which make the application and technique dearer. In this context, to characterize the water body reliably, it has been used faster numerical techniques requiring fewer environmental parameters. In this work, there was the study of the water body of the dam Macela in Itabaiana, Sergipe, determining algebraically WQI and STI and using fuzzy logic. The parameters which define the application and water classification according to the criteria and guidelines set by CONAMA resolution No. 357/2005 were used. The indices calculated for water quality of the dam of Macela (IQAR (6.0 - extremely polluted), O-IQA (2,16 - very) bad), PW-IQA (9.49 - minimum quality), CPCB-IQA (20.13 - very bad) and IQARfuzzy (6.3 - extremely polluted)) show that this is extremely polluted and in a hipereutrofia state, making necessary a government intervention, public awareness programs for the water body may be sustainably used.