A crack found in a monolith at Wanapum dam is prompting a drawdown on the Columbia River to its lowest level since 1964 when the dam was built. Water levels at Wanapum dam have been more than 26 feet below normal and levels at Rock Island Dam, about 38 miles upstream of Wanapum and 15 miles south of Wenatchee, have been as much as 7 feet below normal operating levels. The river level behind Rocky Reach Dam, seven miles north of Wenatchee, has not been affected. The drawdown of the reservoirs has reduced (Wanapum) or stopped (Rock Island) power generation at the dams and created challenges for upstream fish migration.
Adult fish ladders at both dams are temporarily non-operational as a result of lowering the Wanapum reservoir. Engineering assessments and design work is underway to identify the options available to allow adult passage at both dams with lower reservoir water levels. Chelan is also determining what river levels would be necessary to allow normal operation of the Rock Island fish ladders without need of modifications to entrances or exits. Additionally, planning is ongoing to develop a trap-and-haul contingency program from Priest Rapids to Rock Island reservoir if necessary as a short-term remedy while ladder modifications are being completed. Adult spring Chinook will start migrating upstream in late April and although the Grant PUD is working as quickly as possible to fix the crack in the dam, the drawdown conditions could last for several months, if not longer. Officials at both Grant and Chelan PUDs are working hard to maintain public health and safety and ensure adult passage upstream. Downstream juvenile passage, which begins around the third week of April is also a consideration with changes in spill rates and reservoir elevations. Non-turbine downstream passage at the dams is primarily through surface spill. The drawdown and possible changes in dam operations is being evaluated to assure that juvenile outmigrants safely pass each project. Both GPUD and CPUD believe the downstream passage routes are currently functional. Another concern has been flow in the Hanford Reach, where in-stream spawning occurs and fry rearing will occur over the next few months. So far Grant PUD has been able to meet flow targets for Hanford Reach despite the challenges faced. Thanks to Shaun Seaman from Chelan PUD and Tom Kahler from Douglas PUD for assistance