Gabriele Farina

At the global level, nearly 70% of freshwater withdrawals is used for irrigation purposes. Additionally, the world population, whose alimentation is based on the products of the agricultural sector, is growing. On this basis, the relevance of the optimization of water volume distribution in the agricultural sector is undeniable. In Lombardy, irrigation takes advantages of the regulated pre-alpine lakes Maggiore, Como, Iseo, Idro and Garda, whose management rules allow to stock rain and snowmelt in winter and early spring and distribute it among the downstream users during late spring and summer when the water demand for irrigation purpose is higher. In this area, the Consorzio di Irrigazione Cremonese (CIC) was founded in 1883, inheriting a pre-existing and ancient channel network whose intakes are provided by the regulation of pre-alpine Lake Iseo and Lake Como. Although the management of these lakes is expected to change under the effects of climate change, on the other hand the management of the irrigation water system is stiff, being based on pure historical custom and relying on the practical experience of a small group of people. In this direction, we believe that building a mathematical model of the distribution network can be essential for enhancing the performance of the whole irrigation system, providing the opportunity to analyze the behavior of the distribution network under a variety of scenarios. This could eventually lead to identify the optimal management rule.

The main objective is to develop a mathematical model able to describe the flow stage and discharge at every point of the entire channel network. The mathematical model will be based on the one-dimensional formulation of the Saint-Venant equations and will be able to perform long unsteady simulations for a set of complex interconnected channels. The geometry of the network will be multi-connected and characterized by a large number of hydraulic structures which affect the flow along the channel network with different regulations of the gates in correspondence of the withdrawal points along the channels.

The one-dimensional Saint-Venant equations governing the unsteady flow in an open channel network must be solved numerically. After a survey of the numerical methods available, we eventually decided to select and implement a solver based on the 1D formulation proposed by Casulli and Stelling (2013).

The expected results are: the development of a general model based on the numerical model proposed by Casulli and Stelling (2013), its application on the channel network managed by CIC, its validation on the basis of the measured data during the last irrigation season and the analysis of the delivery efficiency under different scenario of reduction of intakes following the effects of climate change.