Water scarcity, insufficient freshwater resources to meet the human and environmental demands of a given area. Water scarcity is inextricably linked to human rights, and sufficient access to safe drinking water is a priority for global development. However, given the challenges of population growth, profligate use, growing pollution, and changes in weather patterns due to global warming, many countries and major cities worldwide,…
Glacier, any large mass of perennial ice that originates on land by the recrystallization of snow or other forms of solid precipitation and that shows evidence of past or present flow. Exact limits for the terms large, perennial, and flow cannot be set. Except in size, a small snow patch that persists for more than one season is hydrologically indistinguishable from a true…
Lead poisoning, also called plumbism, deleterious effect of a gradual accumulation of lead in body tissues, as a result of repeated exposure to lead-containing substances. Causes And Symptoms In humans the main sources of lead are usually lead-based paint and drinking water carried through lead pipes; lead-based paints are especially harmful to children who chew on painted toys and furnishings and eat paint peelings…
Chlorine (Cl), chemical element, the second lightest member of the halogen elements, or Group 17 (Group VIIa) of the periodic table. Chlorine is a toxic, corrosive, greenish yellow gas that is irritating to the eyes and to the respiratory system. · · atomic number 17 atomic weight 35.453 melting point −103 °C (−153 °F) boiling point −34 °C (−29 °F) density…
Germ theory, in medicine, the theory that certain diseases are caused by the invasion of the body by microorganisms, organisms too small to be seen except through a microscope. The French chemist and microbiologist Louis Pasteur, the English surgeon Joseph Lister, and the German physician Robert Koch are given much of the credit for development and acceptance of the theory….
Water purification, process by which undesired chemical compounds, organic and inorganic materials, and biological contaminants are removed from water. That process also includes distillation (the conversion of a liquid into vapour to condense it back to liquid form) and deionization (ion removal through the extraction of dissolved salts). One major purpose of water purification is to provide clean drinking water….
Cast iron, an alloy of iron that contains 2 to 4 percent carbon, along with varying amounts of silicon and manganese and traces of impurities such as sulfur and phosphorus. It is made by reducing iron ore in a blast furnace. The liquid iron is cast, or poured and hardened, into crude ingots called pigs, and the pigs are subsequently remelted along with scrap and alloying…
Reservoir, an open-air storage area (usually formed by masonry or earthwork) where water is collected and kept in quantity so that it may be drawn off for use. reservoir Changes in weather cause the natural flow of streams and rivers to vary greatly with time. Periods of excess flows and valley flooding may alternate with low flows or droughts….
Sewer, conduit that carries wastewater from its source to a point of treatment and disposal. The wastewater may be domestic (sanitary) sewage, industrial sewage, storm runoff, or a mixture of the three. Large-diameter pipes or tunnels that carry a mixture of the three types of liquid wastes, called combined sewers, were commonly built in the 19th and early 20th…
Aqueduct, (from Latin aqua + ducere, “to lead water”), conduit built to convey water. In a restricted sense, aqueducts are structures used to conduct a water stream across a hollow or valley. In modern engineering, however, aqueduct refers to a system of pipes, ditches, canals, tunnels, and supporting structures used to convey water from its source to its main distribution point. Such systems…