Mt. Apo has 19 major rivers and 21 creeks draining its 8 major watersheds (PASAlist.1992). Out of the 19 major rivers, only two has studies as reported by SEA-BMB consultants for the Mt. Apo Geothermal Project Environmental Impact Assessment 1991. According to the report, there are two river ecosystems draining the geothermal site namely: (1) Marbel-Matingao river ecosystem- characterized by narrower river channels at highly elevated areas, much faster water flow, clearer water and rock boulder-rich water beds. The aquatic organisms in the area have expectedly lower biological productivity and species diversity. The report also concluded that this river ecosystem provides much less economic and commercial value for its biological production. The study identified 12 species of fish caught in the area; (2) Kabacan River- Pulangi River ecosystem- characterized by a much wider channels at flat areas, relatively much slower water flow, highly turbid waters and sandy mud river beds.