The park is compossed of two major watersheds. About half of the area drains to the Phetchaburi River, which flows to Kaeng Krachan dam at the eastern edge of the park and then down through farmland to the provincial capital of Phetchaburi. The southern haft of the park drains to the Pranburi River, which flows south to the Pranburi dam and then on to the town of Pranburi in Prachuab Khiri Khan Province. Because of abundant rainfall and undisturbed forest cover in these watersheds, the streams, waterfall and rivers of Keang Krachan flow year round.