Utility of the Two-Source Energy Balance (TSEB) model in vine and interrow flux partitioning over the growing season

Authors: Kustas, William - Bill; Alfieri, Joseph; NIETO, H. - Institute De Recerca I Tecnologia Agroalimentaries (IRTA); Wilson, Tiffany; Gao, Feng; Anderson, Martha

Submitted to: Irrigation Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2018
Publication Date: 9/14/2018
Citation: Kustas, W.P., Alfieri, J.G., Nieto, H., Wilson, T.G., Gao, F.N., Anderson, M.C. 2018. Utility of the Two-Source Energy Balance (TSEB) model in vine and interrow flux partitioning over the growing season. Irrigation Science. https://doi.org/10.1007/s00271-018-0586-8.
DOI: https://doi.org/10.1007/s00271-018-0586-8

Interpretive Summary: As water supplies for agricultural production become more restricted due to overuse and drought, particularly in arid and semi-arid regions, such as the Central Valley of California, there is a concerted effort to improve irrigation methods to reduce the amount of water lost through soil evaporation (E) versus transpiration (T). This is because for many crops T is correlated to biomass production and ultimately yield while E provides little if any contribution from an agronomic point of view, which is particularly important for high valued perennial crops such as wine grapes. Reliable estimates of vine transpiration relative to the total evapotranspiration (ET) are valuable information for determining vine water use and stress, both of which influence grape yield and quality. While several measurement techniques have been developed to estimate T and E, they are very difficult to extrapolate from the local patch scale to field scale and certainly are not able to extrapolate these estimates to the landscape and regional scales. A remote sensing-based land surface model called the Two-Source Energy Balance (TSEB) model can estimate both vine T and interrow E using land surface temperature (LST), available from satellites, providing field to regional scale applications. This study presents the use of the TSEB model for estimating evapotranspiration (ET) and its partitioning into T and E in vineyards over several growing seasons using local LST observations. The E and T partitioning, expressed as the T/ET ratio, is also estimated at the field scale based on the correlation-based flux partitioning method using flux tower measurements. Comparisons in partitioning between E and T using the TSEB model and the correlation-based flux partitioning method indicated the TSEB model output of T/ET was strongly affected by the estimated vine leaf area or biomass estimates from remote sensing, but there was overall good agreement with flux tower estimates. With LST imagery routinely available from satellites, reliable partitioning of ET into T and E, particularly during the vine growing season, can be used to determine a vine water stress index for irrigation scheduling at the field scale. This has the potential to significantly enhance water conservation and water use efficiency strategies of vineyards and other high valued perennial crops such as fruit and nut orchards.

Technical Abstract: For monitoring water use in vineyards, it becomes important to evaluate the evapotranspiration (ET) contributions from the two distinct management zones: the vines and the interrow. Often the interrow is not completely bare soil but contains a cover crop that is senescent during the main growing season (nominally May-August), which in Central California is also the dry season. Drip irrigation systems running during the growing season supply water to the vine plant and re-wet some of the surrounding bare soil. However, most of the interrow cover crop is dry stubble by the end of May. This paper analyzes the utility of the thermal-based Two-Source Energy Balance (TSEB) model for estimating daytime ET using tower-based land surface temperature measurements over two Pinot Noir (Vitis vinifera ) vineyards at different levels of maturity in the Central Valley of California near Lodi, CA. The data were collected as part of the Grape Remote sensing Profile and Evapotranspiration eXperiment (GRAPEX). Local eddy covariance (EC) flux tower measurements are used to evaluate the performance of the TSEB model output of the fluxes and the capability of partitioning the vine and cover crop transpiration (T) from the total ET or T/ET ratio. The results for the 2014-2016 growing seasons indicate that TSEB output of the energy balance components and ET, particularly, over the daytime period yield relative differences with flux tower measurements of less than 15%. However, the TSEB model in comparison with flux partitioning method overestimates T/ET during the winter and spring through bud break, but then underestimates during the growing season. A major factor that appears to affect this temporal behavior in T/ET is the daily LAI used as input to TSEB derived from a remote sensing product.