Fundamentals of watershed hydrology

This is a primer about hydrology, the science of water. Watersheds are the basic land unit for water resource management and their delineation, importance, and variation are explained and illustrated. The hydrologic cycle and its components (precipitation, evaporation, transpiration, soil water, groundwater, and streamflow) which collectively provide a foundation for how landscapes and water interact are discussed at length. Important hydrologic concepts and methods are described in detail but primarily within the context of forested watersheds since most of the nation's fresh water originates from forest lands. The contents of this paper are designed to provide fundamental hydrologic principles to both citizens and policy makers, with the intention of helping to guide informed watershed management activities.