AquiferAn aquifer is an underground layer of water-bearing material consisting of permeable or fractured rock, or of unconsolidated materials (gravel, sand, or silt). Aquifers vary greatly in their characteristics. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Related concepts include aquitard, a bed of low permeability along an aquifer, and aquiclude (or aquifuge), a solid and impermeable region underlying or overlying an aquifer, the pressure of which could lead to t...
Digital object identifierA digital object identifier (DOI) is a persistent identifier, or persistent handle, used to uniquely identify various objects, standardized by the International Organization for Standardization (ISO). DOIs are an implementation of the Handle System; they also fit within the URI system (Uniform Resource Identifier). They are widely used to identify academic, professional, and government information, such as journal articles, research reports, data sets, and official publications. A DOI aims to resolve to its targ...*As an Amazon Associate I earn from qualifying purchases.