I believe there is little to none below Hecla, the first ditch originates at Seidell's, then several more divert along the way with a lot of private property most of the way to Stonebridge. There may be bits of public land, but I don't remember them being all that camper friendly. Best bet may be 2 nights above Hecla or a layover. You could start at Fisherman's bridge or even in BV to extend the first day. One possibility is Cottonwood Wash, just after the foot bridge, for a long day hike if you like that sort of layover activity.
Others may have some different ideas...