Lake Mead is the largest reservoir in the USA, and 16th largest man-made lake in the world. Lake Mead is formed by the Hoover Dam along the Colorado River. EFDC modeling studies have indicated that water level drawdown plays an important role in thermal stratification and water movement of Lake Mead during receding water levels (Li, 2010). Using the improved ability of EFDC+ to model vertical stratification when using the Sigma-Zed model, a re-calibrated model has been developed. Figure 1 shows the location of the model boundary conditions. Figure 2 demonstrates the very high correlation for the vertical temperature profile between the EFDC+ model and data. Figure 3 shows the location of the drape line for extraction of the horizontal slice through the model domain in Figure 4.