Okanagan Nation Alliance and Okanagan Indian Band have installed sediment baskets in the Middle Shuswap River to monitor fine sediment deposits in salmon spawning gravels. Monitoring began in 2016 when BC Hydro conducted dredging at Wilsey Dam. During dredging, fine sediment was released into the spillway of the dam and Middle Shuswap River below. Our monitoring program is designed to measure fine sediment deposition above and below the dam during the dredge year and during two subsequent years during which no dredging will take place. A comparison of fine sediment deposition between years aims to detect any additional sediment deposited as a result of the dredge.
The scope of this monitoring program is to monitor the behavior of fine sediment (suspended load and deposition) during and after dredging activities in 2016, and for two non‐dredge years (2017/18) during similar time periods.
The objectives of the monitoring program are to:
- Determine whether aquatic life forms and important habitat features, including spawning areas (riffles and glides) and holding pools, are affected by sediment accumulation from the proposed dredging activities;
- Confirm through field data collection and analysis that the modeling results presented by Shearing (2015) for sediment transport downstream of Wilsey Dam are predictive of the observed sediment behavior; and,
- Implement a mechanism for assessing instream turbidity on an on‐going basis during dredging activities to determine the effect of the proposed dredge on fish and to ensure that work can be paused if water quality guidelines are exceeded. Further, an assessment of the freshet variability in turbidity NTU peaks and troughs will inform on the ability of the receiving environment to buffer against sudden increases in turbidity.