The Richfield Canal is a major diversion that begins at a large headgate about 4 miles below Magic Reservoir in Idaho. During the agricultural season it swells with water and for the rest of the year it is essentially dry. When the water is flowing there are also fish that get through the headgates. Due to the large volume of water the Richfield Canal calls for during the growing season, the Big Wood River below the diversion is often dewatered.