Identifying the Stage-Flow Relationship and Seasonal Fluctuations in Flow of the Lower Bear River

The Bear River Fellows Program within the Department of Civil and Environmental Engineering at Utah State University was funded through the National Science Foundation. We extended the data analysis of the previous year_s research at three different sites within the Lower Bear River Basin between the Idaho-Utah state line and Cutler Reservoir on two separate occasions, August 13-16, 2013 and November 16, 2013. Our work included collecting river stage, flow, and water pressure measurements using standard surveying equipment, an Acoustic Doppler Current Profiler (ADCP), and pressure transducers. Part of the objective of each trip was to fill out the relationship between stage and flow at each site, and to see how the pressure, temperature, and flow changed over time. Using the data collected from each location and past trips, we were able to develop a stage-flow relationship for each site. With the additional sites located south of the Stateline where a USGS monitoring site is located, we were able to more accurately locate where water was lost within the Lower Bear River. The pressure transducer data was used to calculate a time-series of water stage. The calculated stage was then converted into a time-series of flow at each location using the linear stage-flow relationship previously calculated. We concluded that there was a positive, linear relationship between stage and flow by interpolating the data from our sites on the Bear River. The analysis of the data is primarily concerned with the change of the river discharge over time and seasonal patterns associated with it. This stage-flow relationship and time-series of flows derived from pressure transducer readings provide new insight into how mass is balanced within the Lower Bear River basin. In essence, this provides a better understanding of effects of human inputs/outputs and changing weather patterns on the flow, and to where the water is actually flowing