EVAPORATION MEASUREMENT FROM FREE WATER SURFACE

Huyen Thi Thanh Dao, Yasushi Mori

Abstract


This paper aims to quantify the amount of water surface evaporation with special regard to the EWM evaporation pan and to relate the direct measurements to the Penman and other empirical equations. Based on the available 10-minute interval data on the EWM pan evaporation and the data on precipitation for the same intervals, the net water surface evaporation was estimated for the period from July 2010 to October 2012 (excluding the time EWM pan did not function in winter). From the processing data, raingauge appeared to underestimate the actual precipitation on average 5:3 times, and malfunction when heavy rains occurred. Thus, the net evaporation was estimated only from the fluctuation of water level in EWM pan. Other available weather data, including the dry/wet bulb temperature, water surface temperature, air humidity, wind speed and short-wave solar radiation were also summarized and corrected. These data were then used as input for the Penman equations to obtain semi-empirical daily values of evaporation from water surface. A comparison between the evaporation rates directly measured and those calculated by different methods shows that different values of albedo would improve the performance of the Penman equations. The result of this study contributed to optimization of the EWM data processing methods and to the analysis of variation of water surface evaporation within the diurnal cycle, as well as over longer periods.


Keywords


evaporation, empirical equations, precipitation, EWM pan

References


Chen, D., Gao, G., Xu, C. Y., Guo, J., Ren, G. - Comparison of the Thornthwaite method and pan data with the standard Penman-Monteith estimate of reference evapotranspiration in China, Climate Research 28 (2006) 123 - 132.

Penman, H.L. - Natural evapotranspiration from open water, bare soil and grass. Proceedings of the Royal Society of London. Series A 193 (1948) 120-146.

Historical weather data in Prague. Online database of Czech Meteorological Institute. http://www.chmi.cz/portal/dt?portal_lang=en&menu=JSPTabContainer/P3_0_Informace_pro_Vas/P3_9_Historicka_data&last=false, accessed online 20th March 2013.

Dolezal, F. - Lecture notes on Transport of water in soil-plant-atmosphere continuum. National University of Ireland, Galway, Ireland (1994).

Lecture on Evapotranspiration.

http://search.boisestate.edu/?q=evapotranspiration&site=boisestate.edu, accessed online 20th March, 2013.

Wilson, G. W, Fredlund, D. G., Barbour, S. L. - The effect of soil suction on evaporative fluxes from soil surface. Canadian Geotechnical Journal 34 (4) (1997) 145-155.

Mekonnen, G. B., Dolezal, F., Matula, S. - Using the Dirichlet boundary condition for soil evaporation at all times. Private communication (2012).

Monteith, J.L., Unsworth, M.H. - Principles of environmental physics. Second edition. Edward Arnold, London. ISBN: 9780713129311 (1990) 291.

Chow, VenTe - Handbook of Applied Hydrology: A Compendium of Water Resources Technology, McGraw Hill.ISBN-10: 0070108102 (1964) 1450.

Knozova, G., Roznovsky, J., Kohut, M. - Comparison of evaporation time series measured by evaporimeter GGI 3000 and that calculated by the FAO method. (In Czech). Bioklimatologiesoucasnosti a budoucnosti (2005).

WMO - Guide to meteorological instruments and methods of observation, 7th edition. World Meteorological Organization. Switzerland. ISBN 978-92-63-10008-5 (2008) 681.

Allen, R.G., Pereira, L.S., Raes, D., Smith, M. - Crop evapotranspiration: Guidelines for computing crop water requirements. FAO Irrigation and Drainage Paper, No. 56. FAO. Rome. ISBN 92-5-304219-2 (1998) 300.

Martinez, J.M.M., Alvarez, V. M, Gonzalez-Real, M. M, Baille, A. - A simulation model for predicting hourly pan evaporation from meteorological data. Journal of Hydrology 318 (2005) 250-261.

Valiantzas, J.D. - Simplified versions for the Penman evaporation equation using routine weather data. Journal of Hydrology 331 (2006) 690 - 702.




DOI: https://doi.org/10.15625/2525-2518/58/3/14223 Display counter: Abstract : 23 views.

Refbacks

  • There are currently no refbacks.


Index: Google Scholar; Crossref; VCGate; Asean Citation Index

Published by Vietnam Academy of Science and Technology