Case study: Multicriteria assessment of drought mitigation measures

The proactive approach to drought management is based on measures devised and implemented before, during, and after the drought event, according to a planning strategy rather than within an emergency framework. The measures taken before the initiation of a drought event consist of long-term measures oriented to improve the reliability of the water supply system to meet future demands under drought conditions. The measures taken after a drought is forecasted or starts are short-term measures that try to mitigate the impacts of the particular drought on the basis of a contingency plan. Selection of the preferable mix of long-term and short-term measures can be accomplished through multicriteria decision analysis (MCDA), which enables the comparison of alternatives on the basis of appropriate quantitative and/or qualitative assessment criteria. In this paper, a methodology for the assessment of drought mitigation measures based on a combined use of simulation models and MCDA is applied to a water supply system located in eastern Sicily, Italy. The system comprises two reservoirs and several diversion dams and hydropower plants, and its main uses are irrigation and municipal water supply. First, a simulation model is applied to evaluate the effects of several drought mitigation alternatives consisting of a mix of long- and short-term measures. Then, MCDA is applied to rank the different alternatives on the basis of economic, environmental, and social criteria, taking into account the process of coalition formation among stakeholders on the basis of their different point of view. The results confirm the applicability of the proposed multicriteria methodology for a transparent comparison of drought mitigation measures to be adopted as a support for the decision making process.