Groundwater Contamination — Definition

Definition

Groundwater contamination is the presence or introduction of substances or organisms that impair groundwater quality for a specified use. Contaminants may come from human activities, such as leaking waste systems and agricultural inputs, or from natural interactions between water and geological materials.

Clear-looking water is not proof of chemical or microbial safety. Groundwater also differs from a sealed underground tank: it moves through connected pores and fractures, so pollutants can travel beyond their entry point.

Assessing contamination requires identifying the substance, its concentration, the pathway and the applicable use, rather than assuming that all underground water is naturally protected.