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ARS Home » Plains Area » Bushland, Texas » Conservation and Production Research Laboratory » Soil and Water Management Research » Research » Publications at this Location » Publication #388154

Research Project: Precipitation and Irrigation Management to Optimize Profits from Crop Production

Location: Soil and Water Management Research

Title: Comparison of ET estimates from a surface layer scintillometer and a large weighing lysimeter

item Marek, Gary
item MOORHEAD, JERRY - Lindsay Corporation
item Colaizzi, Paul
item Evett, Steven - Steve
item Gowda, Prasanna
item Brauer, David - Dave

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2021
Publication Date: 9/15/2021
Citation: Marek, G.W., Moorhead, J.E., Colaizzi, P.D., Evett, S.R., Gowda, P.H., Brauer, D.K. 2021. Comparison of ET estimates from a surface layer scintillometer and a large weighing lysimeter [Abstract]. Presented virtually for ICARDA/FAO Webinars on Measuring Evapotranspiration, September 15, 2021. Virtual.

Interpretive Summary:

Technical Abstract: Accurate estimates of actual crop evapotranspiration (ET) are important for effective irrigation water management, especially in arid and semi-arid regions. Common ET sensing methods include Bowen Ratio, Eddy Covariance (EC), and scintillometry. Large weighing lysimeters are considered the standard for direct measurement of ET, however, they are expensive to install and maintain. Although EC and scintillometers are less costly and relatively portable, EC has known energy balance closure discrepancies. Previous scintillometer studies used EC for ground-truthing, but no studies considered comparisons with weighing lysimeter measurements. In this study, a Surface Layer Scintillometer (SLS) was evaluated for accuracy in determining ET (ETsls), as well as sensible and latent heat fluxes, by comparing values with those obtained from a large weighing lysimeter in Bushland, TX. The SLS was positioned over irrigated grain sorghum (Sorghum bicolor (L.) Moench) for the period of July 29 – August 17, 2015 and over grain corn (Zea mays L.) for the period of June 23 – October 2, 2016. Results showed poor correlation for sensible heat flux, however, much better correlation with ET, with r2 values of 0.83 and 0.87 for hourly and daily ETsls, respectively. The accuracy of the SLS was comparable to other ET sensing instruments with an RMSE of 0.13 mm per hour (31 precent) for hourly ETsls; however, summing hourly values to a daily time step reduced the ETsls error to 14 percent (0.75 mm per day). This level of accuracy indicates that potential exists for the SLS to be used in some water management applications. As few studies have been conducted to evaluate the SLS for ET estimation, or in combination with lysimetric data, further evaluations would be beneficial to investigate the applicability of the SLS in water resources management.