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.
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
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
Heat exchanger: A component that
is utilized to remove heat from or ad heat to a liquid.
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all the hydrogen atoms have been replaced by deuterium.
Law: A way of
calculating the solubility of a gas in a liquid, based on temperature and partial
pressure, by means of constants.
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.
A water system that supplies
piped water to a single residence.
Humidification: The addition
of water vapor to air.
The rate at which water
can move through a permeable medium.
general, the direction of groundwater flow due to changes in the depth of the
Hydrocarbon: Organic compounds
that are built of carbon and hydrogen atoms and are often used in petroleum
power plant in which the energy of falling water is used to spin a turbine generator
to produce electricity.
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
Hydroelectricity: Electric energy
produced by water-powered turbine generators.
A gas emitted during organic
decomposition by a select group of bacteria, which strongly smells like rotten
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.
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.
unit: Is a geographic
area representing part or all of a surface drainage basin or distinct hydrologic
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
Hydrophobic: Having an aversion
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.
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.
exerted by or existing within a liquid at rest with respect to adjacent bodies.
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.
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.