Modelling a complex lowland irrigation channel network to optimize management operation under future scenarios of climate change

Irrigation in northern Italy takes advantage of the Maggiore, Como, Iseo, Idro and Garda pre-alpine lakes, whose management rules and structures allow to stock rain and snowmelt outside the irrigation season and share it among the downstream users during late spring and summer. Consorzio Irrigazioni Cremonesi founded in 1883 (CIC in the following) is the most important irrigation consortia in the province of Cremona (northern Italy) in terms of amount of discharged water for irrigation purposes and manages a channel network that dates back to the 16^th century. The maximum discharge derived from the Oglio river and the Adda river by CIC is 57.8 m³/s transported to the different withdrawal points (271) by an open channel network with a length of approximately 261 km. The water distribution provided by CIC is regulated by a complex and rigid timetable of the water turn, which defines the amount of water delivered to each user and the time duration. The intakes of the channel network are provided by the regulation of pre-alpine Lake Iseo and Lake Como, whose level regulation dates back to 1930 and was defined by law considering a set of conflicting constraints as well as the water demand of the irrigated areas. The water distributed by CIC provides a set of ecological services that go beyond simple irrigation.  Although the management of these Lakes is expected to change under the effects of the climate change, on the other hand the management of the irrigation water system is very stiff, being based on pure historical custom and relying on the practical experience of a small group of people. Accordingly, it is likely that this traditional management will become unsuitable in the future and practical experience could be of little use in search of new optimized water distribution frameworks. To manage this transition, CIC is building a mathematical model of the channel network that will be used to test different management options, following the reduction of available discharge caused by different conditions of the lake. The mathematical model, based on the one-dimensional formulation of the Saint-Venant equations, should be able to perform long time simulations for a set of complex interconnected channels in order to capture the different regulations of the gates in correspondence of the withdrawal points along the channel and to take into account the large number of structures which affect the flow along the channel network.