Optimal reservoir sizing in on-demand irrigation networks: Application to a collective drip irrigation network in Spain

Optimal reservoir sizing in on-demand irrigation networks with a minimum cost was obtained, taking into account the variability of pressure and flow rate demanded by the network during the irrigation season. With this aim, a model called DRODIN (Design of Reservoirs of regulation in On-Demand Irrigation Networks) was developed under a holistic approach. That obtain the optimal design and management (minimum total annual cost, CT) of the water abstraction systems in an integrated manner to include the aquifer along with the pumping station, reservoir and pumping and distribution pipes in a collective irrigation network. This tool has been applied to an on-demand irrigation network located in Spain with 171 ha of drip irrigation in vineyard and olive crops. The optimal reservoir volume is approximately 5000 m3, and the CT for water lift (WL) = 100 m (the most common case for this aquifer) is 325 € ha−1 yr−1. The energy cost is the primary component of CT, both in the abstraction and the water supply to the irrigation network, representing between 57% and 80%. The operation of the pumping station determines the size of the reservoir and the annual costs of the water supply to the network for a given water supply guarantee. The CT increases linearly with the WL, primarily because of the increase in energy costs (Ce), although there is a clear relation between the investment costs (Ca), Ce and the reservoir size, which is only possible to analyse with tools such as DRODIN.