Estimation of Evaporation from Class A Pan in Semi-Arid Climatic Conditions by Penman and Kohler-Nordenson-Fox (KNF) Models

Abstract

The climatic parameters needed to estimate evaporation are not easily obtained in many regions for various reasons. By obtaining reliable data, estimation of evaporation for irrigation planning and protection of water resources can be made with less data and easily. In this study, the evaporation from the Class A evaporation vessels, which are used for the estimation of evaporation and developed for this purpose, are estimated by comparing the values measured in meteorological stations and the evaporation through Penman (PM) and Kohler-Nordenson-Fox (KNF) equations, and their performance in semi-arid climatic conditions is evaluated comparatively. For this purpose, climate data received from the Meteorological Station in Siirt province, located in the Southeastern Anatolia Region of Turkey, was used as input in the analysis of the models. Outputs optained from models were statistically evaluated and the root mean squared error (RMSE), mean absolute error (MAE), percentage of error (PE), mean ratio (MR) and determination coefficient (R2) parameters were taken as statistical evaluation criteria. At the end of the study, the best R2 value in the daily comparison was obtained from the EPM-Epan comparison in 2015 and 2016 with 0.8783 and 0.8062, and the RMSE values in this year were calculated as 1.35 and 1.32. In the monthly comparison, the same equation showed the best performance. According to these results, Penman equation used in this study is recommended because it gives lower RMSE values in semi-arid climate conditions in order to estimate evaporation from class A evaporation vessel at daily and monthly levels.

Keywords

• evaporation vessel
• model
• semiarid
• siirt
• reference plant water consumption