Increasing use of biofuels is driving scientists to search for ways to balance global needs for both food and fuel. There is a need to evaluate corn and next generation bioenergy crops like forage sorghum and switchgrass to compare their productivity and water use efficiency. This will help us identify bioenergy crops which are well suited for water-limited environments. The recently developed Aquacrop model is suitable for such analysis because it is specifically designed to predict crop response under water limitations. Field experiments with forage sorghum and switchgrass are being conducted at three sites in Oklahoma, representing different levels of water limitation.  Canopy growth is monitored from emergence to maximum canopy cover at an interval of every two weeks with digital images processed using SamplePoint software.  Aquacrop canopy growth parameters and water stress threshholds are optimized to find a best fit between observed and predicted canopy growth and development.  The calibrated model will then be used to estimate the yields of crops under different water stress scenarios. Calibrated model parameters and simulation results for switchgrass and forage sorghum will be presented.