Perennial/safe/sustainable yield

A specified rate of groundwater pumping that can be sustained for an indefinite period of time without impairing hydrogeologic and ecologic processes, characteristics, or functions existing within a groundwater basin. Examples of impacts to hydrogeologic and ecologic processes, characteristics, and functions include (but are not limited to) alterations to basin-scale flow paths (direction and magnitude); significant drawdown of groundwater surface elevations; decreases in hydrostatic pressures; and decreased connectivity with surface features such as springs, wetlands, and phreatic vegetation. Quantifying perennial/safe/sustainable yields is a non-trivial task that is often done by examining basin-scale information on groundwater recharge, discharge, and storage processes that is obtained through the combination of extensive field-data collection and numerical modeling.