Nowadays the dimension of a reservoir should consider the determination of the minimum capacity that the reservoir has to possess, necessary to regularize the yield based on the
demand. One of the main parameters that characterize a dam is its height that, inside of an economical analysis, influences the cost of the reservoir water and according to an
analysis of hidrological efficiency, influences the regularized. The present work proposes a methodology for the previous dimension of a reservoir, that uses numeric techniques of
optimization, for determination of the height of a dam, with the objective of minimizing the cost of the water. This procedure was applied to the Rosário reservoir built by PROURB (Project of Urban Development and Administration of the water resources of the State of Ceará). The height found for the reservoir was of 20.70 m, with yield of 29.73 hm3/ano
resulting in a cost of the water of R13.97/1000m3.Atualmente,odimensionamentodeumabarragempartedadeterminac\ca~odacapacidademıˊnimaqueoreservatoˊriotemquepossuir,necessaˊriapararegularizarumaquantidadequeeˊestipuladacombasenademandanecessaˊriapararegia~o,fixando,posteriormente,suaaltura,independentedocustodeconstruc\ca~o.Umdospara^metrosprincipaisquecaracterizamumabarragemeˊasuaaltura,que,dentrodeumaanaˊliseecono^mica,influencianocustodoreservatoˊrioedentrodeumaanaˊlisedeeficie^nciahıˊdrica,influencianavaza~oregularizada.Opresentetrabalhopropo~eumametodologiaparaopreˊ−dimensionamentodeumabarragem,queutilizateˊcnicasnumeˊricasdeotimizac\ca~oparadeterminac\ca~odasuaaltura,tendo,comoobjetivo,minimizarocustodaaˊgua.EsteprocedimentofoiaplicadonabarragemdoRosaˊrio,reservatoˊrioconstruıˊdopeloPROURB(ProjetodeDesenvolvimentoUrbanoeGesta~odosRecursosHıˊdricosdoEstadodoCearaˊ).Encontrou−seumaalturaoˊtimaglobalparaala^minad’aˊguade20,70m,comumavaza~oderegularizac\ca~ode29,73hm3/anoresultandonumcustodaaˊguadeR 13,97/1000m3
