Evaluation of Evapotranspiration from Eddy Covariance Using Large Weighing Lysimeters
AbstractEvapotranspiration (ET) is an important component in the water budget and used extensively in water resources management such as water planning and irrigation scheduling. In semi-arid regions, irrigation is used to supplement limited and erratic growing season rainfall to meet crop water demand. Although lysimetery is considered the most accurate method for crop water use measurements, high-precision weighing lysimeters are expensive to build and operate. Alternatively, other measurement systems such as eddy covariance (EC) are being used to estimate crop water use. However, due to numerous explicit and implicit assumptions in the EC method, an energy balance closure problem is widely acknowledged. In this study, three EC systems were installed in a field containing a large weighing lysimeter at heights of 2.5, 4.5, and 8.5 m. Sensible heat flux (H) and ET from each EC system were evaluated against the lysimeter. Energy balance closure ranged from 64% to 67% for the three sensor heights. Results showed that all three EC systems underestimated H and consequently overestimated ET; however, the underestimation of H was greater in magnitude than the overestimation of ET. Analysis showed accuracy of ET was greater than energy balance closure with error rates of 20%–30% for half-hourly values. Further analysis of error rates throughout the growing season showed that energy balance closure and ET accuracy were greatest early in the season and larger error was found after plants reached their maximum height. Therefore, large errors associated with increased biomass may indicate unaccounted-for energy stored in the plant canopy as one source of error. Summing the half-hourly data to a daily time-step drastically reduced error in ET to 10%–15%, indicating that EC has potential for use in agricultural water management. View Full-Text
Share & Cite This Article
Moorhead, J.E.; Marek, G.W.; Gowda, P.H.; Lin, X.; Colaizzi, P.D.; Evett, S.R.; Kutikoff, S. Evaluation of Evapotranspiration from Eddy Covariance Using Large Weighing Lysimeters. Agronomy 2019, 9, 99.
Moorhead JE, Marek GW, Gowda PH, Lin X, Colaizzi PD, Evett SR, Kutikoff S. Evaluation of Evapotranspiration from Eddy Covariance Using Large Weighing Lysimeters. Agronomy. 2019; 9(2):99.Chicago/Turabian Style
Moorhead, Jerry E.; Marek, Gary W.; Gowda, Prasanna H.; Lin, Xiaomao; Colaizzi, Paul D.; Evett, Steven R.; Kutikoff, Seth. 2019. "Evaluation of Evapotranspiration from Eddy Covariance Using Large Weighing Lysimeters." Agronomy 9, no. 2: 99.
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.