American Journal of Water Resources
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American Journal of Water Resources. 2018, 6(6), 212-216
DOI: 10.12691/ajwr-6-6-1
Open AccessArticle

Determining the Effective Distance Spatially for Sharing the Climatic Data Relating to Reference Evapotranspiration

Homayoon Ganji1, and Takamitsu Kajisa1

1Graduate School of Bioresources, Mie University, 1577 Kurimamachiya-cho, Tsu City, Mie 514-8507, Japan

Pub. Date: December 09, 2018

Cite this paper:
Homayoon Ganji and Takamitsu Kajisa. Determining the Effective Distance Spatially for Sharing the Climatic Data Relating to Reference Evapotranspiration. American Journal of Water Resources. 2018; 6(6):212-216. doi: 10.12691/ajwr-6-6-1


The estimation of reference evapotranspiration (ET0) with the FAO-Penman-Monteith method faces challenges in some places due to its high data demand. To overcome this challenge some methodologies recommended by FAO. However, sharing the nearby station’s data is another way to estimate ET0 more accurate in some cases than that of using the FAO’s recommendation. In this paper, the important matter is the determination of an effective distance (Xc) which is the upper limit of distance for data sharing between the stations. ∆ET0(st) which is the average errors between the two stations given by the measured data is theoretically very small if the distance is zero. ∆ET0(Alt) which is the error produced from the alternative data given by FAO’s recommendation is equal to ∆ET0(st) at Xc. By using the data form 48 metrological stations in Japan, we examined this concept in the case of three kinds of data. The results confirmed, there was Xc exited along the investigated distance at which ∆ET0(st) was smaller than ∆ET0(Alt). This was the case corresponding to the solar radiation and actual vapor pressure. Xc was found smaller than the minimum distance in the case of wind data. It is, therefore, possible to use the FAO’s alternative wind data.

effective distance climatic variables reference evapotranspiration geostatistical technique error theory

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