Determining Hourly Evaporation Measurement Accuracy of Small Pans in Comparison with Class-A Pan


  • Mohammad Amir Azimi
  • Mohammad Javad Manshti
  • Amir Ghods Motahari
  • Amin Karami
  • Kourosh Roshtami


evaporation pans, weather station, small pans, water resources, Class-A pan


Because of their convenience and low costs, various types of evaporation pans have been used as a common instrument for measuring evaporation. These pans differ from each other in terms of shape and size. When it comes to tropical areas with high evaporation and short supply of water, refilling evaporation pans on a daily basis is a big challenge. Thus, big pans cannot be easily used in such environments because long term data collection requires proximity to water resources near the weather station. An alternative solution in such conditions is utilizing smaller pans. The present study aimed at comparing the accuracy of evaporation data obtained from evaporation pans with minimized diameters and those collected from standard Class-A pan. It also intended to find out the factors that could influence the accuracy of the collected data. To this end, four cylindrical evaporation pans with diameters of 60, 45, 30, and 15cm and the depth of 25cm were designed. Evaporation heights of these pans were compared with that of Class-A. RMSE and MBE indices as well as t-test results showed that minimizing pan diameter will increase evaporation height, hence reducing the accuracy of obtained data. It was also discovered that, out of all the small pans, the pan with the 60cm diameter is the most suitable evaporation measurement instrument.


Stanhill, G. “Is the Class A evaporation pan still the most practical and accurate meteorological method for determining irrigation water requirements?â€,Agricultural and Forest Meteorology, vol. 112, no. 3, pp.233-236, 2002.

Jacovides, C.P. “Statistical procedures for the evaluation of evapotranspiration computing modelsâ€, Agricultural Water Management, vol. 27, no. 3, pp.365-371, 1995.

Jarraud, M. “Guide to Meteorological Instruments and Methods of Observation (WMO-No. 8)â€, World Meteorological Organisation: Geneva, Switzerland, 2008.

Masoner, J. R. Stannard, D. I. Christenson, S. C. “Differences in Evaporation Between a Floating Pan and Class A Pan on Land1â€, Journal of the American Water Resources Association, vol.44, no.3, pp.552-561, 2008.


How to Cite

Azimi, M. A., Manshti, M. J., Motahari, A. G., Karami, A., & Roshtami, K. (2015). Determining Hourly Evaporation Measurement Accuracy of Small Pans in Comparison with Class-A Pan. Asian Journal of Applied Sciences, 3(6). Retrieved from