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Water glossary



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Water Glossary - H

  • Habitat: The native environment where a plant or animal naturally grows or lives.

  • Hail: A form of precipitation which forms into balls or lumps of ice over 0.2 inch in diameter. Hail is formed by alternate freezing and melting as precipitation is carried up and down in highly turbulent air currents.

  • Half-life: The time required for a pollutant to lose one-half of its original concentration.

  • Hard water: Water containing a high level of calcium, magnesium, and other minerals. Hard water reduces the cleansing power of soap and produces scale in hot water lines and appliances.

  • Hardness (water): Condition caused by dissolved salts of calcium, magnesium, and iron, such as bicarbonates, carbonates, sulfates, chlorides, and nitrates.

  • Hardpan: A shallow layer of earth material which has become relatively hard and impermeable, usually through the deposition of minerals. In the edwards region hardpans of clay are common.

  • Hazardous waste: Waste that poses a risk to human health or the environment and requires special disposal techniques to make it harmless or less dangerous.

  • Head: The pressure of a fluid owing to its elevation, usually expressed in feet of head or in pounds per square inch, since a measure of fluid pressure is the height of a fluid column above a given or known point.

  • Headgate: The gate that controls water flow into irrigation canals and ditches. A watermaster regulates the headgates during water distribution and posts headgate notices declaring official regulations.

  • Heat exchanger: A component that is utilized to remove heat from or ad heat to a liquid.

  • Heat of vaporization: The amount of heat necessary to convert a liquid (water) into vapor.

  • Heavy metals: Metals that have a density of 5.0 or higher and a high elemental weight. Most are toxic to humans, even in low concentrations.

  • Heavy water: Water in which all the hydrogen atoms have been replaced by deuterium.

  • Henry's Law: A way of calculating the solubility of a gas in a liquid, based on temperature and partial pressure, by means of constants.

  • Holding pond: A small basin or pond designed to hold sediment laden or contaminated water until it can be treated to meet water quality standards or be used in some other way.

  • Homeowner water system: A water system that supplies piped water to a single residence.

  • Humidification: The addition of water vapor to air.

  • Hydraulic conductivity: The rate at which water can move through a permeable medium.

  • Hydraulic gradient: In general, the direction of groundwater flow due to changes in the depth of the water table.

  • Hydrocarbon: Organic compounds that are built of carbon and hydrogen atoms and are often used in petroleum industries.

  • Hydroelectric plant: Electric power plant in which the energy of falling water is used to spin a turbine generator to produce electricity.

  • Hydroelectric power water use: The use of water in the generation of electricity at plants where the turbine generators are driven by falling water. Hydroelectric water use is classified as an instream use in this report.

  • Hydroelectricity: Electric energy produced by water-powered turbine generators.

  • Hydrogen sulfide (H2S): A gas emitted during organic decomposition by a select group of bacteria, which strongly smells like rotten eggs.

  • Hydrogeology: The science of chemistry and movement of groundwater.

  • Hydrograph: A chart that measures the amount of water flowing past a point as a function of time.

  • Hydrologic cycle: The constant circulation of water from the sea, through the atmosphere, to the land, and back to the sea by over-land, underground, and atmospheric routes.

  • Hydrologic unit: Is a geographic area representing part or all of a surface drainage basin or distinct hydrologic feature.

  • Hydrology: The science of waters of the earth; water's properties, circulation, principles, and distribution.

  • Hydrometer: An instrument used to measure the density of a liquid.

  • Hydrophilic: Having an affinity for water.

  • Hydrophobic: Having an aversion for water.

  • Hydropower: Electrical energy produced by falling water.

  • Hydrosphere: Region that includes all the earth's liquid water, frozen water, floating ice, frozen upper layer of soil, and the small amounts of water vapor in the Earth's atmosphere.

  • Hydrostatic head: A measure of pressure at a given point in a liquid in terms of the vertical height of a column of the same liquid which would produce the same pressure.

  • Hydrostatic pressure: Pressure exerted by or existing within a liquid at rest with respect to adjacent bodies.

  • Hygroscopic nuclei: Piece of dust or other particle around which water condenses in the atmosphere. These tiny droplets then collide and coalesce, with as many as 10,000 nuclei contributing to formation of a raindrop.

  • Hypochlorite: An anion that forms products such as calcium and sodium hypo chlorite. These products are often used for disinfection and bleaching.

  • Hypolimnion: Bottom layer of cold water in a lake. Compare epilimnion.

  • Hypoxic waters: Waters with dissolved oxygen concentrations of less than 2 mg/L, the level generally accepted as the minimum required for life and reproduction of aquatic organisms.

Water glossary