Reclamation Information Sharing Environment (RISE)

CE_QUAL W2 modelling report on Clark Canyon Reservoir from S&T Project 19080. Clark Canyon Reservoir (CCR) is in southwest Montana and managed by the Missouri Basin Region’s Montana Area Office. It is constructed at the head of the Beaverhead River, linking its outflow water quality with the river’s. Over the past few years, tailwater releases have resulted in high turbidity levels in Beaverhead River during the late summer and early fall months. This has led to an effort to better understand the transport of sediment out of the reservoir. This report describes the Clark Canyon Reservoir water quality model which was developed to better understand the turbidity dynamics within the reservoir. Section 2 describes the project’s background and overall goals. Section 3 provides a description of the study area along with a conceptual understanding of the water quality dynamics within Clark Canyon Reservoir. Section 4 discusses the development of the water quality model including model rates, settings and calibration. Section 5 provides the calibration modeling results. Section 6 looks at the model’s sensitivity to reservoir water levels and outlet height. Section 7 describes how particle simulations were used to investigate sediment transport in the reservoir and how sediment transport is also impacted by reservoir water levels and outlet height. Section 8 gives a brief summary of the Clark Canyon Reservoir water quality model and the conclusions that can be drawn from the model.