Evapotranspiration of Irrigated and Dryland Cotton Fields Determined Using Eddy Covariance and Penman-Monteith Methods.

The study was conducted in 2008 in the Southern High Plains of Texas. Mobile eddy covariance systems were used to measure the energy balance (EB) components in two farmer’s fields (one drip irrigated and the other dryland). A two dimensional Lagrangian random walk (LRW) model was used to estimate the flux footprint.  Potential Evapotranspiration (PET) was calculated using the modified Penman-Monteith Equation using the weather data collected at the study sites. Results from the eddy covariance measurements were compared with PET estimates obtained using the Penman-Monteith Equation.  Based on this analysis, we derived estimates of the surface resistance for mid- and late-season cotton.  These results were used to derive crop coefficients and stress factors based on remote sensing to evaluate crop water use.