Water and Irrigation Management

Water and Irrigation Management

Trend analysis of ET0 and relative importance of climatic variables on ET0 (Case study: Stations Khorramdareh, Gheidar, and Abbar)

Document Type : Research Paper

Authors
Yagob Dinpashoh
Nazanin Heidari
Water Engineering Department, University of Tabriz, Tabriz, Iran.
10.22059/jwim.2024.367513.1126
Abstract
In this study trends in ET0 and the relative importance of climatic variables on ET0 were analyzed for three stations namely Khorramdareh, Gheidar, and Abbar. The Penman- Monteith FAO-56 method was used to estimate ET0 and the factor analysis method was used to study the effect of climatic variables on ET0. The climatic variables used here were precipitation, maximum air temperature, minimum air temperature, wind speed, relative humidity, and actual sunshine hours. For each of the stations, trends in ET0 were analyzed using the Spearman (SP) and Mann-Kendall (MK) methods. Results showed that in the station Abbar, trends were downward and significant at 0.05 level using both methods. In the station Gheidar, trends were downward and significant at 0.05 level using the MK method, however, the trend was decreasing (insignificant) using the SP approach. The correlation matrix of climatic variables was constructed. The correlation coefficients were tested for their significance. Results showed that all the correlation coefficients in Khorramdareh were significant at 0.05 level. Results of FA indicated that in all the sites, the eigenvalues of the first two factors were more than unity. These two factors accounted for about 83.49 to 86.14 percent of variances in the stations. After Varimax rotation, the factor loadings were calculated. Results showed that in the station Khorramdareh, the Tmax and Tmin were the most sensitive variables affecting ET0. It was the Tmax alone in the Gheidar and Abbar stations. According to the second-factor loadings, the wind speed (in Khorramdareh and Gheidar) and the precipitation (in the station Abbar) were the second most sensitive variables affecting ET0.
Keywords
Evapotranspiration
Mann-Kendall
Spearman
Varimax
Subjects
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Water and Irrigation Management
Volume 15, Issue 1
Spring 2025
Pages 75-91