Bureau of Reclamation
- Sarah Baker, MS student, Bureau of Reclamation
- Edie Zagona and David Neumann, CADSWES
A monthly timestep salinity model of Lake Powell was developed for the Bureau of Reclamation. CE‑QUAL‑W2, a complex water quality and hydrodynamic model, was analyzed to observe temporal and longitudinal trends in salinity and temperature in Lake Powell. Observations of salinity and temperature dynamics were used to understand how salinity was moving through Lake Powell and to develop a monthly timestep salinity model for improved management.
The proposed model is composed of three longitudinal segments and two vertical layers. The epilimnion and hypolimnion separated at the penstock (3,470 ft). The proposed Segmented 2 Layer Salt water quality method was coded into RiverWare. The new method models hydrodynamic flow through each reservoir segment and layer. The hydrodynamic flow balance is then used to compute the reservoir salinity balance and outflow salt concentration. The Segmented 2 Layer Salt method improves Lake Powell outflow salinity compared to the current Well-mixed Salt method. For a 1990–2006 run, the Segmented 2 Layer Salt method had a salinity residual sum of 2,540 mg/L, while the Well-mixed Salt method produced a salinity residuals sum of 5,914 mg/L compared to Lee’s Ferry data. Over the 16-year analysis period, the Well-mixed Salt method overestimated the salt mass released from Lake Powell by 1.34 million tons; the Segmented 2 Layer Salt method only overestimated the salt mass released by 0.55 million tons. This method is now being used in the Colorado River Simulation System (CRSS).