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Skin layer evaporation to account for small precipitation events—An enhancement to the FAO-56 evaporation model


  • Allen, Richard G.


The FAO-56 soil water evaporation model is a simple ‘slab’ model that has been found to produce good estimates of evaporation from bare soil over a range of conditions due to its adherence to conservation of mass and energy. The simplicity of the model makes it straightforward to apply and to parameterize. An enhancement is made to the original formulation to accommodate light wetting events that wet the soil ‘skin’ near the surface and evaporate relatively quickly, even when the underlying soil is dry. In effect, the evaporation process, when the soil skin is wetted, reverts temporarily into stage 1 evaporation. The enhancement utilizes the ‘readily evaporable water’ (REW) term of the original model so that no new parameters are required. The extended model performs similar to the original model in the absence of small precipitation events, but increases the evaporation rate when small events occur. The FAO-56 method with the skin evaporation enhancement is shown to compare well against simulations made using the HYDRUS 1D model that bases evaporation on the Richards equation. The enhanced model also closely followed evaporation recorded by weighing lysimeter for a silt loam soil at Kimberly, Idaho, with root mean square difference of 0.39 and 0.69mmd−1 for two wetting/drying sequences. Total cumulative evaporation during the longest and wettest sequence was estimated at 92% of the measured value.

Suggested Citation

  • Allen, Richard G., 2011. "Skin layer evaporation to account for small precipitation events—An enhancement to the FAO-56 evaporation model," Agricultural Water Management, Elsevier, vol. 99(1), pages 8-18.
  • Handle: RePEc:eee:agiwat:v:99:y:2011:i:1:p:8-18 DOI: 10.1016/j.agwat.2011.08.008

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    References listed on IDEAS

    1. Garcia-Orellana, Y. & Ruiz-Sanchez, M.C. & Alarcon, J.J. & Conejero, W. & Ortuno, M.F. & Nicolas, E. & Torrecillas, A., 2007. "Preliminary assessment of the feasibility of using maximum daily trunk shrinkage for irrigation scheduling in lemon trees," Agricultural Water Management, Elsevier, vol. 89(1-2), pages 167-171, April.
    2. Ortuño, M.F. & Conejero, W. & Moreno, F. & Moriana, A. & Intrigliolo, D.S. & Biel, C. & Mellisho, C.D. & Pérez-Pastor, A. & Domingo, R. & Ruiz-Sánchez, M.C. & Casadesus, J. & Bonany, J. & Torrecillas,, 2010. "Could trunk diameter sensors be used in woody crops for irrigation scheduling? A review of current knowledge and future perspectives," Agricultural Water Management, Elsevier, vol. 97(1), pages 1-11, January.
    3. Moreno, F. & Conejero, W. & Martin-Palomo, M.J. & Giron, I.F. & Torrecillas, A., 2006. "Maximum daily trunk shrinkage reference values for irrigation scheduling in olive trees," Agricultural Water Management, Elsevier, vol. 84(3), pages 290-294, August.
    4. Ortuño, M.F. & García-Orellana, Y. & Conejero, W. & Pérez-Sarmiento, F. & Torrecillas, A., 2009. "Assessment of maximum daily trunk shrinkage signal intensity threshold values for deficit irrigation in lemon trees," Agricultural Water Management, Elsevier, vol. 96(1), pages 80-86, January.
    5. Velez, J.E. & Intrigliolo, D.S. & Castel, J.R., 2007. "Scheduling deficit irrigation of citrus trees with maximum daily trunk shrinkage," Agricultural Water Management, Elsevier, vol. 90(3), pages 197-204, June.
    6. Moriana, A. & Girón, I.F. & Martín-Palomo, M.J. & Conejero, W. & Ortuño, M.F. & Torrecillas, A. & Moreno, F., 2010. "New approach for olive trees irrigation scheduling using trunk diameter sensors," Agricultural Water Management, Elsevier, vol. 97(11), pages 1822-1828, November.
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    Cited by:

    1. Yimam, Yohannes Tadesse & Ochsner, Tyson E. & Kakani, Vijaya Gopal, 2015. "Evapotranspiration partitioning and water use efficiency of switchgrass and biomass sorghum managed for biofuel," Agricultural Water Management, Elsevier, vol. 155(C), pages 40-47.

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    Evaporation; Soil water; Evapotranspiration;


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