This study aimed to identify forest type using geo-informatics in watershed constructed within two dam types including Lower Part of Lam Nam Mun subwatershed, where the run-of-river dam named Pak Mun was constructed, and Lam Dom Noi subwatershed, where storage dam named Sirindhorn was constructed. Forest identification was conducted by visual interpretation method using LANDSAT-8 which acquisition in 2017, combine with several secondary information.
The result showed that most of forest covering around mountain in east of both subwatershed. There are 47.79 square kilometers (4.98% of subwatershed area) in Lower Part of Lam Nam Mun subwatershed, consist of 3 forest types including dry diptercarp forest, dry evergreen forest and fresh water swamp forest, which dry diptercarp forest has the most area (31.85 square kilometers). While Lam Dom Noi subwatershed has forest area more than another one (793.68 square kilometers or 36.14% of subwatershed area), and consist of 4 forest types including dry diptercarp forest, dry evergreen forest, fresh water swamp forest and mixed deciduous forest, which dry evergreen forest has the most area (609.39 square kilometers). Moreover, fresh water swamp forest that covered in Lower Part of Lam Nam Mun subwatershed has area more than Lam Dom Noi subwatershed because Sirindhorn dam is the storage dam, resulting in large inundated area throughout the year, whereas Pak Mun dam is the run-of-river dam and Mun river still annual flood, resulting in more fresh water swamp forest.