FINDING ROBUST SOLUTIONS TO WATER-RESOURCES PROBLEMS

Water resources planners and managers are continually faced with decis ions to be made under uncertainty. In planning problems such as water supply, flood control, and ground-water remediation, the trade-offs am ong expected cost, cost variability, and system performance and reliab ility must be assessed amidst inherent variability and imperfect infor mation. Robust optimization (RO) is introduced as a framework for eval uating these trade-offs and controlling the effects of uncertainty in water resources screening models. Upon the introduction of scenarios, which represent realizations of the random parameters in the model, tw o types of robustness are defined: a policy is optimality-robust if it remains optimal or nearly optimal for all scenarios, and feasibility- robust if it remains feasible or nearly feasible for all scenarios. Ap plications to urban water transfer planning and ground-water quality m anagement are presented, with optimality robustness related to cost va riability and feasibility robustness related to system reliability. Re sults show that RO can be a useful framework for evaluating the intrin sic trade-offs involving risk and finding solutions that hedge against inherent and parameter uncertainty.