Groundwater is an inherent part of the ever-changing hydrosphere in the ecosystem supporting probably half of the world economy. As groundwater fl ows from property to property, through communities, underneath boundaries, and interacts naturally between aquifers and streams, it has multiple uses and can serve many users while moving through the hydrologic cycle. The economics of its use and misuse are interconnected with the larger economy and the allocation of resources through prices in the market as a commodity and unpriced values for public services of the ecosystem to sustain life and societies’ economies around the world. Prices and nonmarket values are infl uenced by government policy and regulation. Human interaction with the resources of the ecosystem through the economy can have a positive, sustainable result or a negative, irreversible outcome. For future sustainability, groundwater to support our economies must essentially be in balance with the other intrinsic factors of the ecosystem. The groundwater environment is a condition of water, a stage in the hydrologic and geologic cycles that we intercept for transient and regular purposes of our human needs. With the exception of some deep formations, groundwater fl ows rather than being compartmentalized for our control. As we have choices at different levels of national, international, watershed, community, business, and individual interest, several key economic principles affecting what and how we decide about groundwater emerge from the previous examination and will be considered here.