Spatial and Temporal Distribution of Irrigation Requirements in the Chao Phraya River Basin, Thailand

Abstract

The tendency towards increasingly-higher water demands than in the past has increased the importance of improving water resource management. Responsible water resource management is facilitated by quantifying the irrigation requirements for given land uses. The goal of this study was to
determine the spatial distribution of the irrigation requirements in the eight sub-basins of the Chao Phraya River basin, Thailand. To achieve this goal, actual evapotranspiration was determined by the SEBAL and the FAO Penman-Monteith equations while precipitation was recorded from TRMM satellite images and rain gauge stations. The irrigation requirement was calculated by subtracting the amount of actual evapotranspiration from the measured precipitation. The results of the study concluded that the Ping, Wang and Yom sub-basins had sufficient precipitation for all land uses. For the Nan, Sakae Krang and Pasak sub-basins, there was sufficient precipitation for all land uses except in areas that had existing irrigation infrastructure and thus there is a need for water that is not naturally supplied to support some land uses. For the Tha Chin and Chao Phraya sub-basins there was insufficient precipitation for all land uses. Additional water for these two sub-basins could be sourced from the surplus water from the Ping, Wang, Yom and Nan sub-basins that flowed into the Chao Phraya sub-basin and could also be diverted to the Tha Chin sub-basin.