Estimation of Soil Water Deficit Using Canopy Temperature with a Water Balance Model.

In this study, crop water stress index of a deficit irrigated maize field at Greeley, Colorado, was calculated using a theoretical approach that relies on canopy temperature measured by infrared thermometry and airborne remote sensing imagery. The calculated crop water stress index was coupled with a water balance model to inversely determine total available water in the root zone (TAWZr). The proposed approach provided estimation of near real time crop TAWZr. In addition, TAWZr was interpolated between the dates of remote sensing inputs in order to obtain daily TAWZr values. The performance of the water balance model with inversely estimated TAWZr was evaluated using soil water deficit measurement and the water balance model with empirical determined TAWZr. The results indicated that water balance modeling with CWSI produced reliable daily TAWZr estimation interpolated between CWSI measurements. These results significantly improved soil water deficit estimation compared to applying just the water balance model with empirical determined TAWZr.