Introduction

The Sheep Ridge ditch diversion, a 4-walled concrete and wooden structure on the Lostine River, a tributary to the Wallowa River, is a barrier to fish passage at low late season summer flows and does not meet fish passage criteria as currently applied by ODFW and National Marine Fisheries Service.  The proposed action will install a roughened channel diversion and fishway to replace the existing structure and provide access to 20-miles of habitat upstream.  Partners include the Sheep Ridge ditch company, ODFW, the Nez Perce Tribe, GRMW and adjacent landowners Bill Norman and the Cherry family.

Prior to the mid-1990’s irrigation ditches in the Lostine River were served by gravel push up dams and from that time forward 5 diversions have been upgraded to engineered, permanent fish passable structures.  A total of 11 ditches appropriate water from the Lostine and the 6 that have not been upgraded either do not inhibit passage or are the most difficult to address.  The 5 diversions that have been upgraded include Tulley-Hill, Clearwater, Miles, & Poley-Allen all completed in the mid to late 1990’s.  The most recent, City of Lostine Diversion was completed in 2012.

The first 4 projects relied on concrete and hard non-native substrate material to both check water for diversion and accommodate passage.  Over time and after several fixes it is apparent that each of these installations has a short lifespan, tend to erode from the bottom up compromising structure integrity, and do not meet current fish passage standards as applied.  The City of Lostine diversion applied a different approach; rather than building an unnatural appearing and functioning structure the existing fish ladder and diversion wall was overtopped with an engineered roughened channel.  This method that tends to lengthen the project footprint results in a natural functioning and appearing structure that allows year round passage, restores natural sediment transport processes, meets State and federal passage criteria, and at this time appear to have better longevity due to the built in flexibility.  Flexibility is realized through the use of boulders to build grade control and natural channel substrate that is designed to deposit and scour based on flow conditions.  The Sheep Ridge diversion is designed to use these same methods supported by successful installations at the Wallowa River/Cross Country Canal (2010), Big Sheep/Buehler (2010), and the City of Lostine (2012) diversion structure replacement projects.  
            
The project is a result of prior funded OWEB project #214-5039 Lostine River/Sheep Ridge Fish Passage Improvement Technical Assistance grant and results are presented in this proposal.  In addition to prior diversion structure replacement experience other activities in the Lostine Watershed have informed the development of this proposed action.  Many decades of stream flow gauging directly above the project site, OWEB and BPA funded for the last 15-years, has allowed for the precise calculation of maximum, average and minimum flows necessary for design purposes.  OWEB projects 208-5076 and 210-5057, Migratory Assessment of Spring Chinook Salmon in the Lostine River Using Radio-Telemetry Techniques, has been essential in the decision to improve passage in the project area.  This empirical data has shown that the Sheep Ridge diversion is a low flow passage barrier, delays passage as river flow declines and contributes to spawning in undesirable habitat below the diversion for Chinook salmon.  Prior to telemetry monitoring the Sheep Ridge diversion was not identified as a significant passage barrier.        

Existing condition

Located 2-miles south of the town of Lostine upstream on the Lostine River is a fish ladder installed by Oregon Department of Fish and Wildlife (ODFW).  This fishway was built in the early 1960’s for the purpose of improving fish passage on the Lostine River at the Sheep Ridge ditch irrigation diversion and to eliminate the need for an annual push-up dam to be constructed.  Push-up dams are a method by which streambed material is piled in stream to check water and divert it down the irrigation canal.  This method while effective at diverting irrigation water is disruptive to the stream, causes erosion and sedimentation, and in the case of full channel-spanning structures, cause a barrier to aquatic organism movement both up and downstream.  Push-up dams are usually washed out during high spring flows and have to be re-built annually.  The upstream end of the 3-walled fishway is just below Sheep Ridge Ditch Company’s wooden check structure that checks water elevation sufficient for the irrigation company to divert water without a push-up dam.  

The wooden diversion structure and concrete fishway is an upstream velocity barrier to all fish at high flow, juvenile upstream movement at low flows due to jump height, and adult Chinook at low flow during the spawning time of year, again due to jump height.  Below the diversion is the fishway, the walls of which span the river, each with two to three notches approximately 3 feet wide.  The elevation difference between each wall is approximately 15 inches, which exceeds fish passage criteria.  At this time the concrete walls are aging, deteriorating and chunks of the top wall have detached.  

The Sheep Ridge diversion is used during the Wallowa Valley irrigation season, which starts on May 1st and ends on September 30th.  At all times of the year this ditch delivers stock water at a much lower rate than during irrigation season.  An ODFW operated fish screen composed of three paddle wheel operated drums is located below the diversion and in the irrigation ditch.

Fish native to the Lostine River include spring Chinook, summer steelhead, rainbow trout, and bull trout as well as other resident species.  Design criteria to pass spring Chinook, bull trout, and steelhead are the most stringent and have been used for design purposes.  Spring Chinook migrate through the Lostine system to their spawning areas between July and mid-September.  Summer steelhead migrate to their spawning areas in late winter and spring.  Bull trout are very sparse in the area and mainly forage during winter and early spring.  However, bull trout use this reach as a migration corridor to access spawning areas in the upper Lostine River from June through September.