Abstract:
The purposes of this study were to determine the change of agiicultural landuse above Lam Phra Phloeng reservoir in the years 1991, 1995 and 2000 and a relationship between the change of agricultural landuse, suspended sediment in the watershed and bed load in the Lam Phra Phloeng reservoir. Little change was found in the area above the reservoir, which was used primarily for growing field crops, such as corn, cassava and sugar cane in more than half of the total area, and the rest of the area were forests, orchards, residences, infrastructures and water body and rice areas. There was a tendency to increasingly substitute field crops with fruit trees, such as mangoes, tamarind and custard apples. Not much change was found in the rice-growing area. The forest area was found to be in the high slope ridge area surrounding the study area.Multiple regression analysis was used to determine the relationship between the change of landuse, the suspended sediment in the watershed and the bed load in the Lam Phra Phloeng reservoir. It was found that landuse for agriculture had an impact on thesuspended sediment in the watershed (R = 0.854) and the bed load in the Lam Phra Phloeng reservoir (R= 0.999).