Watershed is basically when water flowing in a particular geographical area drains/ meets into lake, river or any other water body. Management of this water is known as water shed management.It includes the overall planning proper utilization of watersheds. There are various agencies which run different watershed management programs. These programs aimed at protecting and restoring water quality, controlling water pollution and ensuring adequate water supplies.
Need for watershed management:
Due to human activities and various other natural phenomenon (like soil erosion, etc.) water gets polluted.If this water flowing in a particular area is polluted, then the entire water body with which it meets also gets polluted. Which in turn effects the ecological balance. So there is a great need to manage the watershed which is achieved through watershed management programmes.
So Rainwater harvesting is a type of watershed management.