A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering. School of Civil Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 1999

Most of the irrigation systems in developing countries perform below their potential. There may be numerous factors affecting the performance of these systems. The study was carried out to find the influence of the position of the farm relative to the canal system and the influence of farm size on productivity. The K.rasieo irrigation system in Supanburi province, Thailand was selected for the study. A questionnaire was used to collect primary data from the farmers. Secondary data were collected from the Royal Irrigation Department project office at Krasieo. There are two main canals in the system and both of the command areas under main canals consist of lateral and field canals. All canals were divided into three positions as head, middle and tail. The analysis was done for the three canal levels for 1996 and 1997. For the study area 1997 was a drier year compared to an average year. The irrigation supply to demand ratio, for the system varied from 0.36 to 1.09 in 1997. The variation of water distribution was higher in the Right Bank Command Area. The field canal level income variation with the position was less compared to the main and lateral canal levels. The influence of farm size was not significant in Right Bank and, in the Left Bank Command area the small farms perfo1med better than large farms. In the Krasieo irrigation system the performance was mostly dependend on the type and combination of crops cultivated. Sugarcane farmers got more stable income in wet as well as dry years and paddy cultivating farmers got higher income in wet years.