This chapter gives an overview of environmental quality standards and water quality elements according to the Water Framework Directive and all related guidance documents, Environmental Quality Standards Directive and Water Information System for Europe – WISE GIS Guidance. The chapter explains the main definitions and principles by which surface water and groundwater quality is assessed; it sets out the concepts and procedures that closely drive the development of the aquatic environment protection strategy for the basins for the purpose of preventing the damage to water bodies, as well as protecting, increasing, and rehabilitating the status of all bodies of water, both surface and groundwater ones.