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ARS Home » Plains Area » Fort Collins, Colorado » Center for Agricultural Resources Research » Water Management and Systems Research » Research » Publications at this Location » Publication #317454

Research Project: Management Strategies to Sustain Irrigated Agriculture with Limited Water Supplies

Location: Water Management and Systems Research

Title: SEBAL-A: A remote sensing ET algorithm that accounts for advection with limited data. Part II: Test for transferability

Author
item Mkhwanazi, Mcebisi - Colorado State University
item Chavez, Jose - Colorado State University
item Andales, Allan - Colorado State University
item Dejonge, Kendall

Submitted to: Remote Sensing
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2015
Publication Date: 11/10/2015
Publication URL: http://www.mdpi.com/2072-4292/7/11/15068
Citation: Mkhwanazi, M., Chavez, J., Andales, A., Dejonge, K.C. 2015. SEBAL-A: A remote sensing ET algorithm that accounts for advection with limited data. Part II: Test for transferability. Remote Sensing. 2015, 7(11), 15068-15081; doi:10.3390/rs71115068.

Interpretive Summary: Because the Surface Energy Balance Algorithm for Land (SEBAL) tends to underestimate ET under conditions of advection, the model was modified by incorporating an advection component as part of the energy usable for crop evapotranspiration (ET). The modification involved the estimation of advected energy, which required the development of a wind function. In Part I, the modified SEBAL model (SEBAL-A) was developed and tested on well-watered alfalfa of a standard height. In this Part II, SEBAL-A was tested on different crops and irrigation treatments in order to evaluate its transferability. The estimated ET using SEBAL-A was compared to actual ET values measured using the Bowen Ratio Energy Balance (BREB) system. It was concluded that the modified SEBAL (SEBAL-A) could be used on a wide range of crops if they are adequately irrigated.

Technical Abstract: Because the Surface Energy Balance Algorithm for Land (SEBAL) tends to underestimate ET under conditions of advection, the model was modified by incorporating an advection component as part of the energy usable for crop evapotranspiration (ET). The modification involved the estimation of advected energy, which required the development of a wind function. In Part I, the modified SEBAL model (SEBAL-A) was developed and tested on well-watered alfalfa of a standard height. In this Part II, SEBAL-A was tested on different crops and irrigation treatments in order to evaluate its transferability. The crops used for the test were beans (Phaseolus vulgaris L.), wheat (Triticum aestivum L.) and corn (Zea mays L.). The estimated ET using SEBAL-A was compared to actual ET values measured using the Bowen Ratio Energy Balance (BREB) system. Results indicated that SEBAL-A estimated ET fairly well for beans and wheat, only showing some slight underestimation with a Mean Bias Error (MBE) of -0.7 mm d-1 (-11.3 %) and a Root Mean Square Error (RMSE) of 0.82 mm d-1 (13.9 %) and a Nash Sutcliffe Coefficient of Efficiency (NSCE) of 0.64. When SEBAL-A was tested on fully irrigated corn, it performed well, resulting in no bias, i.e. with MBE of 0.0 mm d-1 and RMSE of 0.78 mm d-1 (10.7 %) and NSCE of 0.82. The model seemed to incur some errors on corn that was either water-stressed or at early stages of growth. It was concluded that the modified SEBAL (SEBAL-A) could be used on a wide range of crops if they are adequately irrigated. It is recommended that the SEBAL-A model be further adjusted to be able to accurately estimate ET under dry conditions.