River basin and watershed are technically, synonymous to each other in terms of ecological functions. Both terminology pertains to an area drained by a stream and its tributaries having a common outlet for surface run – off. The difference between the two is only on the land area, as River Basin covers a basin area of more than 100,000 hectares while the watershed has less than 100,000 hectares.
Per Memorandum Circular 2008 – 05 re: Guidelines in the preparation of integrated watershed management plans issued by the Department of Environment and Natural Resources (DENR), the watershed is further categorized into small, medium and large watersheds. The small watershed has less than 10,000 hectares, while medium watershed range from 10,000 to 50,000 hectares and finally, large watershed has more than 50,000 up to 100,000 hectares only.
River basin or watershed is made up of significant interacting components which include the physical, biotic, and climatic components. The interactions and relationships between and among different systems in the river basin are important and necessary as it maintains and sustains the ecological functions of the environment particularly, the hydrologic or water cycle which enables water to circulate from the seas and streams to the atmosphere and back to the land and so forth.
Many watersheds in the country are already in the state of deterioration, where water is no longer clean and safe due to improper disposal of wastes / garbage, water pollution, siltation, mining and other anthropological activities that weakens the important functions of the watershed. This calls for a concerted effort among all citizens, regardless of race or ethnic, religious or group affiliation, locations, etc.