Scenario Analysis for Optimization of Pumping Schedules in Complex Water Supply Systems Considering a Cost-Risk Balancing Problem

Optimization of pumping schedules in complex supply systems is considered in the paper when defining activation of emergency and costly water transfers under drought risk. In a the context of planning long-range infrastructures with uncertainties and possibility of drought conditions, management optimization requires application of specifically derived optimization models defining decision rules. Particularly, treating the effectiveness of early warning and emergency transfers alleviating droughts, the operating costs required by pump stations stress the system managers to the need of a robust approach defining activation rules. An optimization procedure has been developed based on Scenario Analysis. The model allows identification of the optimal decision rules by balancing the risk of water shortages under different hydrological scenarios and the cost of pumping stations operating and maintenance. Scenario analysis optimization provide the resource management authority with information defining optimal activation thresholds for pumping stations assuring the water demand level fulfilment for users and activities (irrigational, civil, industrial, etc). Furthermore, an energy cost minimization and a reduction of economic damages caused by deficits in the water supply to demands centres has been developed in the optimization model. The optimization model is implemented using the software GAMS IDE, specifically designed for modelling mixed integer optimization problems. The model application has been developed for optimization policy and energy conservation in shortage condition in the South-Sardinia (Italy) water supply system. The obtained results define a cost-risk trade-off considering water shortage probability and minimizing operative costs in shortage conditions.