The Upper John Day River Restoration- Lower Island Ditch Diversion Project, is located in the Upper Mainstem of the John Day River in Grant County approximately 7.3 miles southeast of Prairie City, Oregon. The project replaced two existing push-up diversion dams that provided poor fish passage at low flows.
The push-up diversion dams were constructed from logs, gravel, large rock and rubble. They were subject to risk of high water damage which often required equipment to be used to harvest gravels from the streambed to raise and repair the structures during irrigation season. This frequently created turbidity and disturbed the natural streambed and adjacent vegetation. The structure created a 3.5 foot permanent check above the normal channel slope in the main channel. An ODFW fish screen was located in the delivery ditch approximately 60 ft. below the existing headgate. To meet drum screen submergence criteria the water surface check had to be approximately 4.5 feet above the normal grade of the channel. To satisfy this check requirement a combination of gravel, boards and plastic were used to gain a 1 foot rise above the existing log sills. Head cutting below the existing structure created a 3 plus foot elevation change in water surface. Fish passage over the existing structure is provided only when substantial flow was available and did not satisfy current passage criteria.