A study of global water issues often requires the use of specialized terminology. This glossary defines some of the most common terms used in such discussions.
Acre-foot A measurement of water volume equal to the amount of water required to cover one acre of land to the depth of one foot. One acre-foot is equivalent to 325,851 gallons, or 43,560 cubic feet.
Aquifer A bed of porous rock or sand that holds water and from which water can be extracted.
Arch dam A dam that is usually made of concrete and with a curved shape that is facing upstream.
Best available technology (BAT) A method of water treatment that has been determined to be the most effective such technology for that application.
Blue water A term used to describe groundwater and surface water.
Buttress dam A dam that consists of a sloping concrete wall that faces upstream and that is supported by vertical columns attached to the wall.
Chlorination The application of chlorine to water usually for the purpose of disinfecting that water.
Coliform bacteria A group of bacteria found in soils, in water, and in the intestines of warm-blooded animals. Although usually harmless themselves, they are used as an indicator of the potential presence of disease-causing organisms in water.
Desalination The process of removing dissolved salts from a solution, usually seawater, so that it can be used for human consumption, industrial operations, agriculture, or other purposes.
Drought A period of time with less than normal precipitation that lasts for an extended period of time, such that plants are unable to grow successfully, and widespread death of animals results.
Dysentery A disease especially common among children, often caused by waterborne organisms, characterized by severe diarrhea with passage of mucus and blood.
Economic water scarcity A situation in which natural sources of freshwater may be available to a region, but insufficient efforts have been expended to make those resources available to human inhabitants of the region.
Embankment dam A dam made of unconsolidated materials, such as rock, sand, clay, and/or soil.
Finished water Water that has been treated and is ready to be delivered for use by humans.
Fossil water Water that has been trapped underground in an aquifer for very long periods of times, usually tens or hundreds of thousands or millions of years.
Freshwater Water that contains no or very low amounts of dissolved salts.
Gravity dam A dam made of a dense material, such as concrete, that holds back water largely because of its weight.
Gray water Water required to carry away the waste products of some industrial, municipal, agricultural, or other human activities, that is, polluted water.
Green water Rainwater that falls on the land and soaks into the ground, where it is available for growing plants.
Groundwater Water that occurs beneath the surface of the ground.
Highly saline Saline water that contains 10,000 to 35,000 parts per million of dissolved salts.
Hydrology The science dealing with Earth’s waters, their occurrences, distribution, and circulation through the water cycle.
Infiltration The process by which rainwater falls on the ground, soaks into the earth, and then remains there or slowly travels through the earth.
Maximum contaminant level (MCL) A term used to describe the highest concentration of a substance considered to be safe in drinking water.
Moderately saline Saline water that contains 3,000 to 10,000 parts per million of dissolved salts.
Open defecation The discharge of feces from the body in fields, forests, bodies of water, or other open spaces.
Physical water scarcity The lack of access to potable water because of insufficient natural resources, such as lakes, rivers, and underground reservoirs.
Potable water Water that is safe to drink. More specifically, water that is pure enough to meet certain government standards such as the U.S. Public Health Service Drinking Water Standards (available at http://water.epa.gov/drink/contaminants/upload/mcl2.pdf).
Primary drinking water standards A group of legally enforceable standards designed to protect the general public by limiting the amount of various contaminants found in drinking water.
Prior appropriation Priority in the use of a water resource is determined by the priority of beneficial use or, is sometimes commonly noted, “first in time, first in use.”
Qanat A system consisting of a long sloping underground tunnel that can be used to collect water from underground and deliver it to a holding tank on the surface of the land.
Raw water Water that is taken untreated from a natural source, such as a river or lake.
Reverse osmosis A method that is commonly used in the desalination of water in which water is forced through a semipermeable membrane from a region of low concentration to one of high concentration.
Riparian rights A legal doctrine that allows any person whose property borders on a water resource to have access for any beneficial use to that water.
Saline A water solution containing dissolved salts. Also see slightly saline; moderately saline; highly saline.
Secondary drinking water standards A set of standards designed to protect the public health that are provided as guidelines for water purification technology, but that are not legally enforceable.
Shaduf (or shadoof) A simple kind of water-transferring machine that consists of a long horizontal pole that pivots on a vertical post. A bucket hangs from one end of the horizontal pole and a weight (e.g., a rock) at the opposite end.
Slightly saline Saline water that contains 1,000 to 3,000 parts per million of dissolved salts.
Waterborne disease A type of illness caused by a pathogen (e.g., a virus, bacterium, parasite, chemical, or other potentially harmful material) that occurs in drinking water or water used for recreation (e.g., swimming).
Water risk A measure of the probability and severity of the damage caused by some water-related event to a community, a business, or some other entity.
Water scarcity The lack of a sufficient supply of freshwater or of access to such a supply. Technically, the term is used to describe regions where there are fewer than 1,000 cubic meters of freshwater available per person per year.
Water-stressed A term describing an area with a severe lack of freshwater supplies, usually one with between 1,000 and 1,667 cubic meters per person per year.
Water table An underground region in which the ground is permanently saturated.