Mitigation of drought effects on water supply systems

A simplified model of the water resources system is built to evaluate the threshold values and the management rules. The threshold values are defined considering the probability to satisfy a given fraction of the demand in a certain time horizon, and are validated with a long term simulation that takes into account the characteristics of the evaluated system. The levels and volumes in the different reservoirs are simulated using 30-40 years time series. A demand reduction is related to each threshold level. The rules to manage the system in drought conditions, the threshold levels and the reductions are optimized using long term simulations with different hypothesized states of the system. The critical situations are assessed month by month in order to avoid conditions of total water shortage. Synthetic sequences of flows with the same statistical properties of the historical ones are produced to evaluate the performances of the system. The idea is to test it under a variety of conditions using longer sequences of flows than historically available containing more extreme events than observed. The methodology is applied to the urban area Firenze-Prato-Pistoia in central Tuscany, in central Italy.