Evaluating Management Strategies in Paraguacu River Basin by Analytic Hierarchy Process

An approach is proposed for evaluating water management strategies in river basins. Reasonably large sets of criterions and objectives are manipulated during a three-phase process by appropriate shrinking and enlarging related decision hierarchies. In the first phase an unrestricted set of management interests are grouped into (1) long-term, and (2) middle- and short-term decision context by creating decision hierarchies and evaluating them by the Analytic Hierarchy Process (AHP). After refining the hierarchies by deleting dominated elements, management plans are introduced at their fingertips and so enlarged hierarchies are repeatedly evaluated by AHP in the second phase. Only two bottom levels of hierarchies is necessary to consider by this break-in evaluating procedure. Size of decision hierarchies is rationally preserved in both phases considering limited human abilities in handling numerous decision elements while comparing them, and difficulties in attaining desired decision consistency. The last phase aggregates weights of management plans derived in the second phase for two hierarchies and performs a final ranking of the management alternatives. The Paraguacu river basin in Brazil is used as a case study. This is the most important alluvium in the state of Bahia, which spreads out over 55 thousand square kilometres. Within the basin there are 84 municipalities with nearly 2 million inhabitants. Prevailing water management conditions are semi-arid and major water uses are human and animal supply, irrigation and low river flow augmentation for ecological purposes. Three management plans for a 40-year time horizon were evaluated and ranked.