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Estimating Evaporation from Bare or Nearly Bare Soil |
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| Authors: | R. L. Snyder K. Bali F. Ventura H. Gomez-MacPherson |
| Affiliation: | 11Extension Biometeorologist, Dept. of Land, Air and Water Res., Univ. of California, 1 Shields Ave., Davis, CA 95616. E-mail: rlsnyder@ucdavis.edu 22Farm Advisor, Univ. of California Cooperative Extension, Imperial County, 1050 East Holton Rd., Holtville, CA 92250. E-mail: kmbali@ucdavis.edu 33Res., Dept. of Agronomy, Univ. of Bologna, Via Filippo Re 6-8, 40126 Bologna, Italy. E-mail: fventura@pop.agrisci.unibo.it 44Tech. Ofcr., United Nations Food and Agric. Org., AGPC, Via delle Termi di Carcalla, 00100 Rome, Italy. E-mail: helena.gomezmacpherson@fao.org |
| Abstract: | A model is presented that uses a daily mean evapotranspiration ETo rate to estimate energy-limited (potential or Stage 1) soil evaporation, and it also uses daily mean ETo and a soil hydraulic β factor to estimate soil hydraulic property-limited (Stage 2) evaporation. The model provides good estimates of cumulative soil evaporation on both hourly and daily bases when compared to observed soil evaporation in three field trials. Crop coefficient Kc values from cumulative hourly and cumulative daily soil evaporation estimates and ETo data were comparable. Using a soil hydraulic factor (β = 2.6) in the model gave a fair approximation for the widely used Kc curves for initial growth of crops presented in the United Nations Food and Agricultural Organization's Irrigation and Drainage Paper 24. However, using a site-specific β factor should improve soil evaporation and Kc estimates for site-specific applications. |
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