Energy balance in a crop canopy reflects crop water use and crop responses to incoming solar radiation and soil water status. Correctly simulating surface energy balance is essential for crop modeling. In this study, measured surface energy balance from the Bowen Ratio instrumentation in Colorado is used to calibrate the SHAW energy balance module in RZWQM2. The model simulated canopy temperature is then used to define a water stress factor for the plant growth module in RZWQM2. Simulated crop responses to irrigation using the canopy temperature based water stress factor are compared with those using crop transpiration based water stress factors.