Drought mitigation using operative indicators in complex water systems

The definition of an effective link between drought indicators and drought mitigation measures in a regional water supply systems is a complex problem involving environmental, social and economical factors. The gap between research and practice in this field still limits the application of mathematical modelling tools more than institutional or technological features. In this paper, a methodology is developed to support the decision making process of water authorities facing droughts in complex water systems. The methodology is based on a full integration of optimization and simulation tools. The exploratory power of the optimization allows the rapid estimation of subsets of flow variables related to forecasted demands supplies and shortages that are used as operative indicators of the drought risk in future hydrological scenarios. The simulation model uses these indicators as triggers of mitigation measures in a proactive approach to drought. In the case of an overly optimistic forecast of the hydrological scenario, the proactive approach does not completely eliminate the risk of shortages. In this case, further measures have to be implemented in the water system simulation in a reactive approach to drought. These can include more expensive and higher impact measures to be taken later, after the severity of the drought event has been highlighted. In collaboration with the regional water authorities in southern Italy, the proposed methodology is currently being tested in the Agri–Sinni water system. Early applications to the Agri–Sinni water system are presented in the paper, showing the usefulness of the proposed methodology in mitigating the impacts of drought and selecting an economically efficient combination of proactive and reactive measures.