My paddling club occasionally takes day trips on different sections of the upper Des Moines River. The area we frequent is from Willow's access (near Bradgate) to Humbolt, and from Fort Dodge to the Dolliver Park area- Either trip can be easily done in a day, with plenty of time to rest, explore, or fish. The only portage required in either trip is the Rutland dam, but it's a great place to stretch and have a snack, as you overlook the rushing water and old brick mill.
Boat traffic is generally very light, and the fishing can be good for walleye and catfish. Scenery is nice, with high bluffs, limestone outcroppings in places, and heavily timbered hills throughout many areas.
Plenty of lodging, food, & drink in Fort Dodge.
Put in at Willows Access near Bradgate & take out in Humbolt (or Rutland dam for a slightly shorter trip). Other trip's put in- lower dam in Fort Dodge, and take out at boat ramp in Dolliver Park.