HESS Hydrology and Earth System Sciences HESS Hydrol. Earth Syst. Sci. 1607-7938 Copernicus Publications Göttingen, Germany 10.5194/hess-18-1053-2014 A comparison of methods for determining field evapotranspiration: photosynthesis system, sap flow, and eddy covariance Zhang Z. 1 Tian F. https://orcid.org/0000-0001-9406-7369 1 2 Hu H. 1 Yang P. 1 State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, 100084, China now at: State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, China 18 03 2014 18 3 1053 1072 Copyright: © 2014 Z. Zhang et al. 2014 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://hess.copernicus.org/articles/18/1053/2014/hess-18-1053-2014.html The full text article is available as a PDF file from https://hess.copernicus.org/articles/18/1053/2014/hess-18-1053-2014.pdf

A multi-scale, multi-technique study was conducted to measure evapotranspiration and its components in a cotton field under mulched drip irrigation conditions in northwestern China. Three measurement techniques at different scales were used: a photosynthesis system (leaf scale), sap flow (plant scale), and eddy covariance (field scale). The experiment was conducted from July to September 2012. To upscale the evapotranspiration from the leaf to plant scale, an approach that incorporated the canopy structure and the relationships between sunlit and shaded leaves was proposed. To upscale the evapotranspiration from the plant to field scale, an approach based on the transpiration per unit leaf area was adopted and modified to incorporate the temporal variability in the relationship between leaf areas and stem diameter. At the plant scale, the estimate of the transpiration based on the photosynthesis system with upscaling was slightly higher (18%) than that obtained by sap flow. At the field scale, the estimates of transpiration derived from sap flow with upscaling and eddy covariance showed reasonable consistency during the cotton's open-boll growth stage, during which soil evaporation can be neglected. The results indicate that the proposed upscaling approaches are reasonable and valid. Based on the measurements and upscaling approaches, evapotranspiration components were analyzed for a cotton field under mulched drip irrigation. During the two analyzed sub-periods in July and August, evapotranspiration rates were 3.94 and 4.53 m day<sup>−1</sup>, respectively. The fraction of transpiration to evapotranspiration reached 87.1% before drip irrigation and 82.3% after irrigation. The high fraction of transpiration over evapotranspiration was principally due to the mulched film above the drip pipe, low soil water content in the inter-film zone, well-closed canopy, and high water requirement of the crop.

 References ADC Bioscientific Ltd.: LCi Portable Photosynthesis System: Instruction Manual, ADC BioScientific Ltd., Hoddesdon, UK, 2004. Alfieri, J. G., Kustas, W. P., Prueger, J. H., Hipps, L. E., Evett, S. R., Basara, J. B., Neale, C. M. U., French, A. N., Colaizzi, P., Agam, N., Cosh, M. H., Chavez, J. L., and Howell, T. A.: On the discrepancy between eddy covariance and lysimetry-based surface flux measurements under strongly advective conditions, Adv. Water Resour., 50, 62–78, 2012. Allen, R. G., Pereira, L. S., Raes, D., and Smith, M.: FAO Irrigation and drainage paper No. 56, Food and Agriculture Organization of the United Nations, Roma, Italy, 1998. Allen, R. G., Pereira, L. S., Howell, T. A., and Jensen, M. E.: Evapotranspiration information reporting: I. Factors governing measurement accuracy, Agr. Water Manage., 98, 899–920, 2011a. Allen, R. G., Pereira, L. S., Howell, T. A., and Jensen, M. E.: Evapotranspiration information reporting: II. Recommended documentation, Agr. Water Manage., 98, 921–929, 2011b. Ashraf, M.: Salt tolerance of cotton: Some new advances, Crit. Rev. Plant Sci., 21, 1–30, 2002. Baker, J. M. and Vanbavel, C.: Measurement of mass-flow of water in the stems of herbaceous plants, Plant Cell Environ., 10, 777–782, 1987. Baldocchi, D., Falge, E., Gu, L. H., Olson, R., Hollinger, D., Running, S., Anthoni, P., Bernhofer, C., Davis, K., Evans, R., Fuentes, J., Goldstein, A., Katul, G., Law, B., Lee, X. H., Malhi, Y., Meyers, T., Munger, W., Oechel, W., Paw U, K. T., Pilegaard, K., Schmid, H. P., Valentini, R., Verma, S., Vesala, T., Wilson, K., and Wofsy, S.: FLUXNET: a new tool to study the temporal and spatial variability of ecosystem-scale carbon dioxide, water vapor, and energy flux densities, B. Am. Meteorol. Soc., 82, 2415–2434, 2001. Barry, B. A.: Errors in practical measurement in science, engineering and technology, Wiley, New York, 1978. Bonachela, S., Orgaz, F., Villalobos, F. J., and Fereres, E.: Soil evaporation from drip-irrigated olive orchards, Irrig. Sci., 20, 65–71, 2001. Chabot, R., Bouarfa, S., Zimmer, D., Chaumont, C., and Moreau, S.: Evaluation of the sap flow determined with a heat balance method to measure the transpiration of a sugarcane canopy, Agr. Water Manage., 75, 10–24, 2005. Chavez J. L., Howell, T. A., and Copeland, K. S.: Evaluating eddy covariance cotton ET measurements in an advective environment with large weighing lysimeters, Irrig. Sci., 28, 35-=50, 2009. Ding, R., Kang, S., Li, F., Zhang, Y., Tong, L., and Sun, Q.: Evaluating eddy covariance method by large-scale weighing lysimeter in a maize field of northwest China, Agr. Water Manage., 98, 87–95, 2010. Dugas, W. A.: Comparative measurement of stem flow and transpiration in cotton, Theor. Appl. Climatol., 42, 215–221, 1990. Dugas, W. A., Heuer, M. L., Hunsaker, D., Kimball, B. A., Lewin, K. F., Nagy, J., and Johnson, M.: Sap flow measurements of transpiration from cotton grown under ambient and enriched CO<sub>2</sub> concentrations, Agr. Forest. Meteorol., 70, 231–245, 1994. Evett, S. R., Kustas, W. P., Gowda, P. H., Anderson, M. C., Prueger, J. H., and Howell, T. A.: Overview of the bushland evapotranspiration and agricultural remote sensing experiment 2008 (BEAREX08): a field experiment evaluating methods for quantifying ET at multiple scales, Adv. Water Resour, 50, 4–19, <a href="http://dx.doi.org/10.1016/j.advwatres.2012.03.010">https://doi.org/10.1016/j.advwatres.2012.03.010</a>, 2012. Falge, E., Baldocchi, D., Olson, R., Anthoni, P., Aubinet, M., Bernhofer, C., Burba, G., Ceulemans, R., Clement, R., Dolman, H., Granier, A., Gross, P., Grunwald, T., Hollinger, D., Jensen, N. O., Katul, G., Keronen, P., Kowalski, A., Lai, C. T., Law, B. E., Meyers, T., Moncrieff, H., Moors, E., Munger, J. W., Pilegaard, K., Rannik, U., Rebmann, C., Suyker, A., Tenhunen, J., Tu, K., Verma, S., Vesala, T., Wilson, K., and Wofsy, S.: Gap filling strategies for defensible annual sums of net ecosystem exchange, Agr. Forest. Meteorol., 107, 43–69, 2001. Foken, T.: The energy balance closure problem: An overview, Ecol. Appl., 18, 1351–1367, 2008. Franssen, H. J., Stöckli, R., Lehner, I., Rotenberg, E., and Seneviratne, S. I.: Energy balance closure of eddy-covariance data: A multisite analysis for European FLUXNET stations, Agr. Forest. Meteorol., 150, 1553–1567, 2010. Good, S. P., Soderberg, K., Wang, L., and Caylor, K. K.: Uncertainties in the assessment of the isotopic composition of surface fluxes: A direct comparison of techniques using laser-based water vapor isotope analyzers, J. Geophys. Res., 117, D15301, <a href="http://dx.doi.org/10.1029/2011JD017168">https://doi.org/10.1029/2011JD017168</a>, 2012. Granier, A., Biron, P., and Lemoine, D.: Water balance, transpiration and canopy conductance in two beech stands, Agr. Forest. Meteorol., 100, 291–308, 2000. Ham, J. M., Heilman, J. L., and Lascano, R. J.: Determination of soil-water evaporation and transpiration from energy-balance and stem-flow measurements, Agr. Forest. Meteorol., 52, 287–301, 1990. Hatton, T. J. and Wu, H. I.: Scaling theory to extrapolate individual tree water-use to stand water-use, Hydrol. Process., 9, 527–540, 1995. Heilman, J. L. and Ham, J. M.: Measurement of mass-flow rate of sap in ligustrum-japonicum, Hortscience, 25, 465–467, 1990. Hou, X., Wang, F., Han, J., Kang, S., and Feng, S.: Duration of plastic mulch for potato growth under drip irrigation in an arid region of northwest China, Agr. Forest. Meteorol., 150, 115–121, 2010. Howell, T. A., Evett, S. R., Tolk, J. A., and Schneider, A. D.: Evapotranspiration of full-, deficit-irrigated, and dryland cotton on the northern Texas high plains, J. Irrig. Drain. E.-ASCE., 130, 277–285, 2004. Hu, H., Tian, F., and Hu, H.: Soil particle size distribution and its relationship with soil water and salt under mulched drip irrigation in Xinjiang Province of China, Sci. China Tech. Sci., 54, 1–7, 2011. Katul, G. G., Oren, R., Manzoni, S., Higgins, C., and Parlange, M. B.: Evapotranspiration: A process driving mass transport and energy exchange in the soil-plant-atmosphere-climate system, Rev. Geophys., 50, RG3002, <a href="http://dx.doi.org/10.1029/2011RG000366">https://doi.org/10.1029/2011RG000366</a>, 2012. Kigalu, J. M.: Effects of planting density on the productivity and water use of tea (Camellia sinensis L.) clones I. Measurement of water use in young tea using sap flow meters with a stem heat balance method, Agr. Water Manage., 90, 224–232, 2007. Ko, J., Piccinni, G., Marek, T., and Howell, T.: Determination of growth-stage-specific crop coefficients (<i>K<sub>c</sub></i>) of cotton and wheat, Agr. Water Manage., 96, 1691–1697, 2009. Lei, H. and Yang, D.: Interannual and seasonal variability in evapotranspiration and energy partitioning over an irrigated cropland in the North China Plain, Agr. Forest. Meteorol., 150, 581–589, 2010. Leuning, R., Van Gorsel, E., Massman, W. J., and Isaac, P. R.: Reflections on the surface energy imbalance problem, Agric. Forest. Meteorol., 156, 65–74, 2012. Li, S., Kang, S., Li, F., and Zhang, L.: Evapotranspiration and crop coefficient of spring maize with plastic mulch using eddy covariance in northwest China, Agr. Water Manage., 95, 1214–1222, 2008. Loranty, M. M., Mackay, D. S., Ewers, B. E., Adelman, J. D., and Kruger, E. L.: Environmental drivers of spatial variation in whole-tree transpiration in an aspen-dominated upland-to-wetland forest gradient, Water Resour. Res., 44, W02441, <a href="http://dx.doi.org/10.1029/2007WR006272">https://doi.org/10.1029/2007WR006272</a>, 2008. MacKay, D. S., Ahl, D. E., Ewers, B. E., Gower, S. T., Burrows, S. N., Samanta, S., and Davis, K. J.: Effects of aggregated classifications of forest composition on estimates of evapotranspiration in a northern Wisconsin forest, Global Change Biol., 8, 1253–1265, 2002. Mahouachi, J., Socorro, A. R., and Talon, M.: Responses of papaya seedlings (Carica papaya L.) to water stress and re-hydration: Growth, photosynthesis and mineral nutrient imbalance, Plant Soil, 281, 137–146, 2006. Mengistu, T., Sterck, F. J., Fetene, M., Tadesse, W., and Bongers, F.: Leaf gas exchange in the frankincense tree (Boswellia papyrifera) of African dry woodlands, Tree Physiol., 31, 740–750, 2011. Petersen, K. L., Fuchs, M., Moreshet, S., Cohen, Y., and Sinoquet, H.: Computing transpiration of sunlit and shaded cotton foliage under various water stresss, Agron. J., 84, 91–97, 1992. Sakuratani, T.: A heat balance method for measuring water flux in the stem of intact plants, J. Agr. Meteorol., 37, 9–17, 1981. Sakuratani, T.: Improvement of the probe for measuring water flow rate in intact plants with the stem heat balance method, J. Agrometeorol., 40, 273–277, 1984. Sarlikioti, V., de Visser, P., and Marcelis, L.: Exploring the spatial distribution of light interception and photosynthesis of canopies by means of a functional-structural plant model, Ann. Bot., 107, 875–883, 2011. Sassenrath-Cole, G. F.: Dependence of canopy light distribution on leaf and canopy structure for two cotton (Gossypium) species, Agr. Forest. Meteorol., 77, 55–72, 1995. Silberstein, R., Held, A., Hatton, T., Viney, N., and Sivapalan, M.: Energy balance of a natural jarrah (Eucalyptus marginata) forest in Western Australia: measurements during the spring and summer, Agr. Forest. Meteorol., 109, 79–104, 2001. Stoy, P. C., Mauder, M., Foken, T., Marcolla, B., Boegh, E., Ibrom, A., Arain, M. A., Arneth, A., Aurela, M., Bernhofer, C., Cescatti, A., Dellwik, E., Duce, P., Gianelle, D., van Gorsel, E., Kiely, G., Knohl, A., Margolis, H., McCaughey, H., Merbold, L., Montagnani, L., Papale, D., Reichstein, M., Saunders, M., Serrano-Ortiz, P., Sottocornola, M., Spano, D., Vaccari, F., and Varlagin, A.: A data-driven analysis of energy balance closure across FLUXNET research sites: The role of landscape scale heterogeneity, Agr. Forest. Meteorol., 171–172, 137–152, 2013. Tang, L., Li, Y., and Zhang, J.: Partial rootzone irrigation increases water use efficiency, maintains yield and enhances economic profit of cotton in arid area, Agr. Water Manage., 97, 1527–1533, 2010. Tao, Y.: Contrusting physiological properties of shaded and sunlit leaves, and applying a photosynthesis model for cotton, Nanjing University of Information Science & Technology, Nanjing, 2007. Thanisawanyangkura, S., Sinoquet, H., Rivet, P., Cretenet, M., and Jallas, E.: Leaf orientation and sunlit leaf area distribution in cotton, Agr. Forest. Meteorol., 86, 1–15, 1997. Tolk, J. A., Howell, T. A., and Evett, S. R.: Nighttime evapotranspiration from alfalfa and cotton in a semiarid climate, Agron. J., 98, 730–736, 2006. van Dijk, A., Moene, A. F., and de Bruin, H. A. R.: The principles of surface flux physics: theory, practice and description of the ECPACK library, Internal Report 2004/1, Meteorology and Air Quality Group, Wageningen University, Wageningen, the Netherlands, 99 pp., 2004. Wang, H., Zhang, L., Dawes, W. R., and Liu, C.: Improving water use efficiency of irrigated crops in the North China Plain – measurements and modeling, Agr. Water Manage., 48, 151–167, 2001. Wang, L., Caylor, K. K., Villegas, J. C., Barron-Gafford, G. A., Breshears, D. D., and Huxman, T. E.: Partitioning evapotranspiration across gradients of woody plant cover: Assessment of a stable isotope technique, Geophys. Res. Lett., 37, L09401, <a href="http://dx.doi.org/10.1029/2010GL043228">https://doi.org/10.1029/2010GL043228</a>, 2010. Wang, L., Niu, S., Good, S. P., Soderberg, K., McCabe, M. F., Sherry, R. A., Luo, Y., Zhou, X., Xia, J., and Caylor, K. K.: The effect of warming on grassland evapotranspiration partitioning using laser-based isotope monitoring techniques, Geochim. Cosmochim. Acta, 111, 28–38, 2013. Wang, R., Kang, Y., Wan, S., Hu, W., Liu, S., and Liu, S.: Salt distribution and the growth of cotton under different drip irrigation regimes in a saline area, Agr. Water Manage., 100, 58–69, 2011. Webb, E. K., Pearman, G. I., and Leuning, R.: Correction of flux measurements for density effects due to heat and water vapour transfer, Q. J. Roy. Meteorol. Soc., 106, 85–100, 1980. Williams, D. G., Cable, W., Hultine, K., Hoedjes, J. C. B., Yepez, E. A., Simonneaux, V., Er-Raki, S., Boulet, G., de Bruin, H. A. R., Chehbouni, A., Hartogensis, O. K., and Timouk, F.: Evapotranspiration components determined by stable isotope, sap flow and eddy covariance techniques, Agr. Forest. Meteorol., 125, 241–258, 2004. Wilson, K. B., Hanson, P. J., Mulholland, P. J., Baldocchi, D. D., and Wullschleger, S. D.: A comparison of methods for determining forest evapotranspiration and its components: sap-flow, soil water budget, eddy covariance and catchment water balance, Agr. Forest. Meteorol., 106, 153–168, 2001. Wilson, K., Goldstein, A., Falge, E., Aubinet, M., Baldocchi, D., Berbigier, P., Bernhofer, C., Ceulemans, R., Dolmanh, H., Field, C., Grelle, A., Ibrom, A., Lawl, B. E., Kowalski, A., Meyers, T., Moncrieffm, J., Monsonn, R., Oechel, W., Tenhunen, J., Valentini, R., and Verma, S.: Energy balance closure at FLUXNET sites, Agr. Forest. Meteorol., 113, 223–243, 2002. Zhang, J., Wang, Y., Mao, W., Dong, Q., and Zhao, Y.: Dynamic Simulation of leaf area in cotton canopy, Trans. Chin. Soc. Agric. Mach., 38, 117–120, 2007. Zhang, Z., Hu, H. C., Tian, F., Hu, H. P., Yao, X., and Zhong, R.: Soil salt distribution under mulched drip irrigation in an arid area of northwestern China, J. Arid. Environ., 104, 23–33, <a href="http://dx.doi.org/10.1016/j.jaridenv.2014.01.012">https://doi.org/10.1016/j.jaridenv.2014.01.012</a>, 2014. Zhou, S., Wang, J., Liu, J., Yang, J., Xu, Y., and Li, J.: Evapotranspiration of a drip-irrigated, film-mulched cotton field in northern Xinjiang, China, Hydrol. Process., 26, 1169–1178, <a href="http://dx.doi.org/10.1002/hyp.8208">https://doi.org/10.1002/hyp.8208</a>, 2011.