Map of the Brianza lakes and the Adda water system
Levels of Lakes Pusiano, Annone and Lecco, with a note on cutting behind Trezzo
On blue-prepared paper Leonardo draws in red chalk and ink a survey map of the watercourses and lakes north-east of Milan, naming the Lambro, Serio and Adda rivers and the lakes of Pusiano, Erba, Annone, Sala and Lecco, along with Ogiona, Valmagrera and the Tre Corni. The notes record relative water-levels: Annone stands 22 braccia above Lecco and Pusiano 20 braccia above Annone, so Pusiano lies 42 braccia above Lecco. A further note observes that to dam the Adda onto the plain of Cascano one must cut deep behind Trezzo. A small geometric doodle appears at upper left.
On this page
Survey map of the Brianza lakes and rivers
The sheet maps the watercourses and lakes above Milan: the Lambro, Serio and Adda rivers and the lakes of Pusiano, Erba, Annone, Sala and Lecco, with Ogiona, Valmagrera and the Tre Corni named. Lake Pusiano is noted as pouring into the lakes of Serio, Annone and Sala.
Relative lake levels and a cut behind Trezzo
Water-levels are set down: Annone stands 22 braccia above Lecco and Pusiano 20 braccia above Annone, so Pusiano is 42 braccia above Lecco. The Tre Corni rise 16 braccia above the Adda's surface, and to dam the river onto the plain of Cascano one must cut deep behind Trezzo.