Comparision of weighing lysimeter ET with a two-source energy balance model

Authors: Colaizzi, Paul; O`Shaughnessy, Susan; Evett, Steven - Steve; Marek, Gary; Brauer, David; Copeland, Karen; Ruthardt, Brice

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/31/2023
Publication Date: 10/26/2023
Citation: Colaizzi, P.D., O'Shaughnessy, S.A., Evett, S.R., Marek, G.W., Brauer, D.K., Copeland, K.S., Ruthardt, B.B. 2023. Comparision of weighing lysimeter ET with a two-source energy balance model [abstract]. ASABE 2nd Global ET Symposium, October 23-27, 2023, University Park, Pennsylvania. Paper No. 23006.

Interpretive Summary: Irrigated crop production contributes forty percent of food and fiber production on twenty percent of farmland worldwide, but this is threatened by declining water resources. This has made agricultural water conservation increasingly important for food security. Water conservation can be enhanced by avoiding over-irrigation of crops, but this requires estimates of actual crop water use. Scientists at USDA-ARS, Bushland, Texas made significant improvements to an existing computer model to estimate crop water use more accurately. The model uses weather data and plant leaf temperature data, which have become more available in recent years due to better sensors and better cellular data services. The model was tested against actual field measurements of crop water use for several crops, including corn, cotton, and soybean. The crops were irrigated by sprinkler and subsurface drip irrigation. The model was also tested during fallow periods. The improved accuracy of the model will result in increased water conservation without compromising crop yield or farm income.

Technical Abstract: Thermal-based energy balance models can calculate evaporation, transpiration, and evapotranspiration and can be used to detect crop water stress. These variables can inform irrigation management decisions that have resulted in increased crop water productivity. A two-source energy balance (TSEB) model has been refined following several previous studies at the USDA-ARS weighing lysimeter facility at Bushland, Texas, USA. The present study includes a comprehensive test of the refined TSEB where ET calculated by the TSEB was compared to ET from mass changes measured by four weighing lysimeters. Crops included corn, cotton, and soybean, and fallowed surfaces. Each crop was irrigated by sprinkler or subsurface drip irrigation, and each irrigation method was applied at two of the four lysimeters. The TSEB used surface temperature data at each lysimeter; surface temperatures were derived by stationary wireless infrared thermometers that viewed each lysimeter from five or six directions. Micrometeorological data was obtained from a nearby grass reference site. Discrepancies in ET calculated by the TSEB or measured by lysimeter will be assessed in terms of irrigation method, crop, IRT view angle, and IRT vegetation view factors.