A Water Diversion Procedure to Irrigation for the Lower Chao Phraya Basin in Dry Season

Abstract

Diversion of water meeting an irrigation plan is fundamental to management of water resources in the lower Chao Phraya Basin during dry season efficiently. This study therefore proposes a procedure for water diversion from the Chao Phraya Dam that consists of a combination of a quantile regression between observed upstream-water-level of the dam and diversion discharge record (1997 – 2018) and a probability distribution (lognormal distribution) of historical capital water of the Bhumibhol and Sirikit dams for the period (1997 - 2018). The adopted regression is more suitable than ordinary least-square one because the present research is interested in obtaining the function that is conditional on quantile. In addition, when dealing with outlier condition, its estimation is also more robust. The application of the proposed procedure starts with using the distribution function to find a level of probability for the available capital water. Later, it considers the developed regression to estimate a rate of diversion discharge with the probability level and a water level observation. Results of applying to the Noi River (the Boromtart Gate) and the Tha-Chin River (the Polathep Gate) have shown that the procedure yields the size of irrigated areas that are closer to a plan than that of existing ones.