Stage height data was downloaded from California Department of Water Resources Water Data Library (https://wdlbeta.water.ca.gov/WaterQualityDataLib.aspx) for 1998-2021 to overlap with the period of Yolo Bypass Fish Monitoring Program monitoring. Stage height at Fremont Weir is most often used to determine whether the Yolo Bypass is inundated. The defined monitor stage, or stage at which flow occurs in the bypass area, can be found on the California Data Exchange Center (https://cdec.water.ca.gov/stageInfo.html). If the stage height is greater than or equal to 32 feet at Fremont Weir the flow spills over to the Yolo Bypass or “overtops”, which greatly increases the amount and quality of flooded habitat in the Yolo Bypass.
The Sacramento River at Fremont Weir (West End) Station #A02170 was used to track Fremont Weir’s stage height. Occasionally, data was missing from this station so an additional station of the Sacramento River at I Street Station #A02100 was used to track I Street Bridge’s stage height. The monitor stage at I Street Bridge is 17 feet. Additionally, Yolo Bypass near Lisbon Weir Station #B91560Q stage height data was incorporated. The Lisbon Weir 15-minute stage height data was averaged by day and values exceeding 27.5 feet (Peak of Record) were excluded. The Lisbon Weir overtops at 13 feet and was also used to determine if the Yolo Bypass is inundated. Incorporation of Lisbon Weir accounts for time in which the Fremont or I street Bridge may have just finished overtopping but the Bypass has not yet drained. The Yolo Bypass would therefore still be inundated. These data were collected by the Surface Water Data Section at the North Central Region Office of DWR. They used a “bubbler system” which is a state-of the art technology accurate to 0.01 feet. The system consists of the following three components: Compressor (Make: YSI/Xylem, Model: H-3551), Data Control Platform (Make: YSI/Xylem, Model: H-350-XL), GOES Radio Telemetry (Make: YSI/Xylem, Model: H-2221-V2). Stage height data from these three stations were compiled, and conditional statements based on stage height were used to determine whether each station was overtopping, and thus whether the Yolo Bypass was inundated. If any of the stage heights were greater than their overtopping height (Fremont Weir 32 ft, I St Bridge 17ft, and Lisbon Weir 13ft), the Yolo Bypass was considered to be inundated.
