Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): C. Liu; G. SunS. G. McNulty; S. Kang
    Date: 2015
    Source: Transactions of the ASABE
    Publication Series: Scientific Journal (JRNL)
    Station: Southern Research Station
    PDF: View PDF  (1.0 MB)

    Description

    Accurately estimating evapotranspiration (ET) is essential for orchard managers to design irrigation schedules and conserve water resources in semi-arid environments where water is often the limiting factor for successful production. Improving water use efficiency helps irrigation scheduling and thus benefits water resource management and the sustainability of the local economy. This study examined three existing ET models that were developed based on the Shuttleworth- Wallace model (SW) for estimating ET from sparsely covered crops in the arid Shiyang River basin (mean annual precipitation = 164 mm) in northwest China. We improved the existing clumping model (C model), a modified version of the SW model that simulates soil evaporation under the tree canopy and from bare soils outside of the canopy using a fixed bare soil/canopy area ratio. Our new ET model (the seasonal clumping model, or Cj model) considered the hourly dynamics of the bare soil surface area both under and outside of the tree canopy in an irrigated apple (Malus domestica Borkh. cv. Golden Delicious) orchard. The Cj model provided an improved estimate of soil evaporation by simulating soil surface areas based on hourly changes in canopy shade patterns and the canopy gap fraction. We validated the SW, C, and Cj models with ET fluxes measured by multiple methods, including sap flow of apple trees, and ET estimated by the micro-lysimeter and soil water balance methods for the 2008, 2009, and 2010 growing seasons. Soil water content, canopy characteristics (e.g., leaf area index), and leaf stomatal conductance were also measured periodically to parameterize the model. The growing season total ET rates estimated by the sap flow and micro-lysimeter method were 667, 674, and 583 mm in 2008, 2009, and 2010, respectively. The relative simulation errors of soil evaporation for the Cj, C, and SW models were 5%, 10%, and 30%, respectively. The absolute error for transpiration modeled by Cj (0.58 mm d-1) was significantly lower than for the C model (0.65 mm d-1) on a biweekly time scale. The growing season ET simulated by the Cj model was 628, 624, and 572 mm during 2008, 2009, and 2010, respectively, and the soil evaporation was 24% to 32% of the total ET. Over all, the Cj model was an improvement over the other two existing models for estimating apple orchard ET with a sparse tree cover. Our study also suggested that a supplement of 400 to 500 mm of irrigation water was essential to grow productive apple trees in the study region. The new model was successful in simulating the soil evaporation process and estimating the additional amount of water required to supplement natural rainfall by irrigation. The Cj model developed from this study was suitable for mature orchards or sparse forests with a bare soil surface, and it could efficiently estimate the water demand for irrigation scheduling.

    Publication Notes

    • You may send email to pubrequest@fs.fed.us to request a hard copy of this publication.
    • (Please specify exactly which publication you are requesting and your mailing address.)
    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

    Citation

    Liu, C.; Sun, G.; McNulty, S. G.; Kang, S. 2015. An Improved evapotranspiration model for an apple orchard in northwestern China. Transactions of the ASABE. : 1253-1264. https://doi.org/10.13031/trans.58.11088.

    Cited

    Google Scholar

    Keywords

    Apple trees, Evapotranspiration, Sap flow, Shuttleworth-Wallace model

    Related Search


    XML: View XML
Show More
Show Fewer
Jump to Top of Page
https://www.fs.usda.gov/treesearch/pubs/59050