This research is devided into three parts, the study of water resources, water quality and water utilization of Changwat Rayong during the dry season. It is found that there are many water resources available in Rayong. Most of them are streams which come from the northern part of Rayong flowing towards the sea in the southern. Rayong River and Pra-sae River are two main rivers in Rayong and have adjoining basins. There is high potential of developing reservoir system from the two rivers nowaaday many projects are in the planning stage of water resource development. Most of the people in rural area use rain water and water from dug wells for consumption and domesric uses. But in the dry season they are mostly dried up. In the northern part of Rayong shortage of water occurs during the dry season while the salinity intrusion and hardness of water are the main problems in the southern. Generally, water quality is quite good, but in some part of Rayong, there are some heavy metals such as manganese (Mn) in water from dug wells, which are toxic for drinking. Most of water resources for the cultivation is rainfall. Water resources for small industries are provided by the owners themselves. In case of the Eastern Seaboard Development, industrial projects require more fresh water about 63-72 MCM per year from Dok Krai Reservoir and the Nong Kho Reservoir. In the first part of the development, there is some trend of fresh water shortage. Supplementary water will have to be drawn Nong Pla Lai Reservoir and Klong Yai Reservoir. It is believed that the Nong Pla Lai Project will be helpful to solve the problem of shortage of fresh water in these areas.
