Water systems planning: the optimization perspective

The progressive technological and economic development of societies has given rise to a global increase in the demand for water. In their efforts to meet the demand for good quality water, in adequate quantities, when and where it is needed, humans have been tampering with the natural hydrological cycle. Decision models play an important role in dealing with water resources planning problems by integrating simultaneously all the relevant aspects (physical, hydrological, technological, financial, etc.) characterizing these problems. This paper presents an overview, pointing out the new trends regarding the decision models commonly used to solve the most important water systems planning problems. The achievements accomplished during these last three decades and the impacts of the improvements attained in software and hardware are highlighted. The gap between theory and practice in this field, and the reasons for such a circumstance are also discussed.