These many rivulets pour out the same water, or a little less, than if the water passed through one single great channel; and there is no other difference except in the time of excavating their soil when they are made, because it only passes along the banks but is not thrown out of the ditch, which cannot happen when such water is in a single stream. But it is a useful thing to have them made by the course of the water itself, by shifting them beneath the soil. And from this follows the ease of crossing for those who pass such banks.

d - f - a - K - c - b g - h. By the ninth [proposition], e f g h, the curvature of the water's course will keep the greater depth on the concave side than on the convex part that lies opposite it. And by this you can be certain that such a master canal will always have the convenience of distributing its waters into the small rivulets placed on the convex side. The road c d should cross the said rivulets at right angles, so that the bridges built over these rivulets be shorter, because they will be crossed by shorter timbers. And by the fifth [proposition] of the "maximum depths of rivers," the water of the river should be drawn off at the beginning of its current, where the river curves least. The depths of the canals should be as much as the least depth of the river, that is, at the beginning of the current. And you will be able to judge that all the water passing through that part of the river will be able to pass through canals of the same depth, their widths, joined together, being similar to the width of the beginning of said current; and then the rivulets will hold all the water of the river, but as much less deep as those canals are shorter than the course the water of the whole river previously made.