CE-QUAL-W2 Hydrodynamic and Water Quality Model of the Cedar River Municipal Watershed
Author | : |
Publisher | : |
Total Pages | : 220 |
Release | : 2020 |
Genre | : Water quality |
ISBN | : |
The laterally averaged, two-dimensional model CE-QUAL-W2 was used to develop a water quality model of the Cedar River Municipal Watershed as a reservoir management and climate change scenario tool. The 90,638-acre watershed, located 56 kilometers southeast of Seattle, WA, provides drinking water to over 1.4 million people. The watershed relies on two waterbodies for storage, Chester Morse Lake and the Masonry Pool. The Masonry Dam is the main storage structure in the watershed. The Cedar River flows downstream from the Masonry Dam for 57 kilometers to Lake Washington. The reservoir model simulated Chester Morse Lake and the Masonry Pool. The river model simulated the Cedar River from the Masonry Dam for 21 kilometers to the Landsburg Diversion Dam. Model inputs included bathymetric data, stream inflows and temperatures, outflows from the Masonry Dam, water quality constituent concentrations, and meteorological data. The system was modeled over two separate time periods: January 1, 2005 to December 31, 2008 and January 1 to December 31, 2015. Water level calibration was completed by comparing observed water surface elevations in Chester Morse Lake and the Masonry Pool. Flow calibration was completed by comparing streamflow gages in the Cedar River. Water temperature calibration used temperature data from twelve locations for the 2005-2008 model and six locations for the 2015 model. Water quality calibration used data from five locations for the 2005-2008 model and ten locations for the 2015 model. The model simulated water temperature on the hourly timescale with an RMSE of 0.60-0.65°C in the reservoir models and an RMSE of 0.48-0.71°C in the river models. The model simulated dissolved oxygen profile concentrations in Chester Morse Lake with an RMSE of 0.51-0.66 mg/L in the reservoir models and dissolved oxygen discrete sample concentrations in the Cedar River with an RMSE of 0.32-0.36 mg/L in the river models. Other water quality parameters were simulated within observed ranges for all parameters. Three climate change scenarios considered changes in meteorological data and inflow data. Two reservoir management scenarios considered changes in reservoir storage and spring refill level. The impact on fish habitat under each scenario was determined for the reservoir model and the river model.