米兰公国
Having become part of the Duchy of Milan and already protected for centuries by a chain of fortresses and castles, the shores of the Olona increased their development: the mills multiplied, while the contribution to irrigation remained significant. Such an intensive use of water required the Duchy of Milan to issue specific regulations (the so-called "Statutes of the streets and water of the Milan countryside"): this was the first time in 1346 and then in 1396.