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Water Glossary - E

  • Ecosphere: Total of all the ecosystems on the planet, along with their interactions; the sphere of air, water, and land in which all life is found.

  • Ecosystem: A system formed by the interaction of a group of organisms and their environment.

  • Edwards aquifer: An arch-shaped belt of porous, water bearing limestone composed of the Comanche Peak, Edwards, and Georgetown formations trending from west to east to northeast through Kinney, Uvalde, Medina, Bexar, Comal, Hays, Travis, and Williamson counties.

  • Edwards outcrop: Where the Edwards and associated limestone formations are found at the surface. This area is also referred to as the Recharge Zone.

  • Effective porosity: The portion of pore space in saturated permeable material where the movement of water takes place.

  • Effective precipitation: The part of precipitation which produces runoff; a weighted average of current and antecedent precipitation "effective" in correlating with runoff. It is also that part of the precipitation falling on an irrigated area which is effective in meeting the requirements of consumptive use.

  • Effluent: The sewage or industrial liquid waste that is released into natural water by sewage treatment plants, industry, or septic tanks.

  • Ejector: A device used to inject a chemical solution into wastewater during water treatment.

  • Electrical charge: The charge on an ion, declared by its number of electrons. A Cl- ion is in fact a Cl atom which has acquired an electron, and a Ca++ ion is a Ca atom, which has lost two electrons.

  • Electrodialysis: A process which uses an electrical current and an arrangement of permeable membranes to separate soluble minerals from water. It is often used to desalinate salt or brackish water.

  • Electrolyte: Substance that dissociates into ions when it dissolves in water.

  • Elutriation: Freeing sludge of its mother liquor by washing it with water.

  • Emulsifier: A chemical that helps suspending one liquid in another.

  • Emulsion: Dispersion of one liquid in another liquid, occurs when a liquid in insoluble.

  • Endangered species: One having so few individual survivors that the species could soon become extinct in all or part of its region.

  • End-of-pipe techniques: Techniques for water purification that serve the reduction pollutants after they have formed.

  • Enrichment: When the addition of nutrients, such as nitrogen and phosphorus, from sewage effluent or agricultural runoff to surface water, greatly increases algal growth.

  • Enteric viruses: A category of viruses related to human excreta found in waterways.

  • Environment: All of the external factors, conditions, and influences that affect an organism or a community.

  • Environmental assessment: The critical appraisal of the likely effects of a proposed project, activity, or policy on the environment, both positive and negative.

  • Environmental monitoring: The process of checking, observing, or keeping track of something for a specified period of time or at specified intervals.

  • EPA: Environmental protection agency.

  • Epilimnion: Warm, less dense top layer in a stratified lake. Compare hypolimnion.

  • Erosion: The wearing down or washing away of the soil and land surface by the action of water, wind, or ice.

  • Escarpment: The topographic expression of a fault.

  • Eschericha coli (E. coli): Coliform bacterium that is often associated with human and animal waste and is found in the intestinal court. It is used by health departments and private laboratories t measure the purity of water.

  • Estuarine waters: Deepwater tidal habitats and tidal wetlands that are usually enclosed by land but have access to the ocean and are at least occasionally diluted by freshwater runoff from the land (such as bays, mouths of rivers, salt marshes, lagoons).

  • Estuarine zone: Area near the coastline that consists of estuaries and coastal saltwater wetlands.

  • Estuary: Regions of interaction between rivers and nearshore ocean waters, where tidal action and river flow create a mixing of fresh water and saltwater. These areas may include bays, mouths of rivers, salt marshes, and lagoons. These brackish water ecosystems shelter and feed marine life, birds, and wildlife.

  • Euphotic zone: Surface layer of an ocean, lake, or other body of water through which light can penetrate. Also known as the zone of photosynthesis.

  • Eutrophic: Having a large or excessive supply of plant nutrients (nitrates and phosphates). Compare oligotrophic.

  • Eutrophic lake: Shallow, murky bodies of water that have excessive concentrations of plant nutrients causing excessive algal production.

  • Eutrophication: The natural process by which lakes and ponds become enriched with dissolved nutrients, resulting in increased growth of algae and other microscopic plants.

  • Evaporation: Process by which water is changed from a liquid into a vapor. See also evapotranspiration and transpiration.

  • Evaporation ponds: Areas where sewage sludge is dumped and dried.

  • Evapotranspiration: A collective term that includes water discharged to the atmosphere as a result of evaporation from the soil and surface-water bodies and as a result of plant transpiration. See also evaporation and transpiration.

  • External cost: Cost of production or consumption that must be borne by society; not by the producer.

  • Extinction: Complete disappearance of a species because of failure to adapt to environmental change.

Water glossary