Combining metamodelling and stochastic dynamic programming for the design of reservoirs release policies

Increasing worldwide water withdrawal for irrigation purposes requires a more efficient management of water resources and an accurate description of irrigation water demand. This paper, with the aim of thinking ‘in blue and green water terms’, proposes a new approach for the design of release policies in reservoir systems serving irrigation districts. It is based on the solution of an optimal control problem, where the dynamics of the irrigation demand is modelled through a metamodel, i.e. a simple model identified on the basis of the data produced by a distributed-parameter, conceptual model. The metamodel inherits the physical description of the distributed-parameter model and, at same time, is sufficiently simple to allow the solution of the optimal control problem with stochastic dynamic programming. The proposed approach is tested on a real-world case study, the management of the Lake Como system, for which it provides satisfactory results.