Until the advent of the railway, the only way to transport goods was the waterway. Thus goods could be transported on the seine from the place where it began to be navigable to its estuary. The problem had just connected the rivers to each other. For this to happen, canals had to be created that crossed land and obstacles. We talk about junction channels at sharingbief. 

Thus the Briare canal joins the Loire River with the Seine via the Loing, crossing the reliefs that separate them. Locks were created to cross the elevation and supply the canal with water from the divide bay by reservoir ponds.