ScienceAsia 33 (2007): 245-252|doi: 10.2306/scienceasia1513-1874.2007.33.245

Evaluation of Spatial and Temporal Reference Evapotranspiration in the Chao Phraya River Basin, Thailand

Preeyaphorn Kosa and Kobkiat Pongput*

 
ABSTRACT: In the hydrological cycle and in water use, evapotranspiration is one of the most important components because it represents a loss of usable water from the hydrological supply. The purposes of this research are to examine the temporal trend of reference evapotranspiration and pan evaporation for the upper region, the lower region, and the whole catchment of the Chao Phraya River Basin, and to consider the spatial and temporal distribution of monthly reference evapotranspiration. To achieve these purposes, daily reference evapotranspiration from 1971 to 2002 was computed for each weather station using the FAO Penman-Monteith method. The average of monthly reference evapotranspiration in each weather station was calculated. Thereafter, this monthly reference evapotranspiration reference point for evapotranspiration was interpolated using the Co-Kriging interpolation to obtain a spatial value. From the results of this research it can be concluded that the trends of both reference evapotranspiration and pan evaporation in all the regions have decreased from 1971 to 2002 and that the spatial and temporal distribution of mean monthly reference evapotranspiration are affected by the changes in the meteorological variables for each month and for each different region.

KEYWORDS: spatial, temporal, reference evapotranspiration, Co-Kriging.

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