A watershed is the area of land from which precipitation or surface water flow is drained into a receiving water body. The term is roughly analogous to a "drainage basin", and are often used interchangeably. While primarily describing the geologic/geographic drainage patterns of water, a more holistic view of the word watershed incorporates all the biotic and abiotic communities and processes contained in the drainage basin. Watersheds may be referred to as the sum of the area, drainage patterns, and environment of a given waterway or waterway segment. This book reviews research on watersheds including the climatic change impacts on the hydrologic dynamics of watershed systems; the watershed approach for resource conservation, environment quality and food security in the Indian Himalayas and others.