Submitted to: National Decennial Irrigation Conference
Publication Type: Proceedings
Publication Acceptance Date: 12/5/2010
Publication Date: 12/5/2010
Citation: French, A.N., Hunsaker, D.J., Thorp, K.R. 2010. Remote sensing of evapotranspiration over crops using combined airborne and ground-based observations. National Decennial Irrigation Conference. IRR 10-9789.
Interpretive Summary: Efficient use of water for irrigation is vital meeting the challenges of increased food demand and water scarcity. Knowing how much water is needed and how to manage shortages will be extremely important for farmers who will have to compete with urban users. In the last ten years the joint technological development of remote sensing and methods to use the resulting images of farm land, has greatly increased over the previous ten years. Now, remote sensing data can be acquired routinely every few days. Unfortunately, however, this technology still cannot meet daily requirements for farmers, especially when skies are cloudy. One possible solution is to combine remote sensing and ground-based data sets. A demonstration of the method at Maricopa, Arizona shows that crop water use might be accurately forecast up to ten days before new remote sensing images are needed. Results from this research will be useful for water managers and irrigation engineers seeking ways to conserve and map water use over crops.
Technical Abstract: Remote sensing of evapotranspiration (ET) over crops could be valuable for managing scarce water resources, especially for irrigated lands. In the past decade remote sensing techniques have advanced to allow frequent estimation of ET at spatial scales useful for many farms. These techniques include wider availability of higher resolution image data, development of remote sensing-based energy balance models, and deployment of lower-cost ground-based radiometric systems. Used together, ET can be estimated at daily to weekly time steps, despite occasional adverse sky conditions. The benefits of combining these newer capabilities will be demonstrated using experimental data collected over a cotton crop at Maricopa, Arizona in 2003. The way data were acquired and combined was similar to the way sensors are currently deployed in local wireless networks. The potential for future operational ET estimation at farm-scales will be discussed.