Terms and Definitions - G to L

G

Giardia Lamblia. A flagellate protozoan that causes the severe gastro-intestinal illness Giardiasis, when it contaminates drinking water.

Giardiasis. A disease that results from an infection by the protozoan parasite Giardia Intestinalis, caused by drinking water that is either not filtered or not chlorinated. The disorder is more prevalent in children than in adults and is characterized by abdominal discomfort, nausea, and alternating constipation and diarrhea.

Grab Sample. Typically, a single water or air sample drawn over a short time period. As a result, the sample is not representative of long-term conditions at the sampling site. This type of sampling yields data that provides a snapshot of conditions or concentrations at a particular point in time.

H

Heavy Metals. (1) Those metals that have high density; in agronomic usage these include copper, iron, manganese, molybdenum, cobalt, zinc, cadmium, mercury, nickel and lead. These substances are considered toxic at specified concentrations. (2) Metals having a specific gravity of 5.0 or greater; generally toxic in relatively low concentrations to plant and animal life and tend to accumulate in the food chain. Examples include lead, mercury, cadmium, chromium, and arsenic.

Heterotrophic Organism. Organisms that are dependent on organic matter for food.

Holding Pond. An impoundment used to temporarily store solid and liquid wastes and polluted runoff from concentrated livestock or waste areas until they can be safely utilized, evaporated or otherwise disposed of. Sometimes called a retention pond.

Holding Time. (Water Quality) The time allowed between removal of samples from water sources for bacteriological analysis and the processing of those samples.

Hyporheic Zone. Zone of substrate in a stream bottom extending 1 to 2 meters (3.3 to 6.6 feet) below the surface of the stream bed. In gaining and in losing streams, water and dissolved chemicals can move repeatedly over short distances between the stream and the shallow subsurface below the streambed. The hyporheic zone is comprised of the resulting subsurface environments, which contain variable proportions of water from groundwater and surface water. These zones can be active sites for aquatic life, for example, the spawning success of fish may be greater where flow from the stream brings oxygen into contact with eggs that were deposited within the course bottom sediment or where stream temperatures are modulated by groundwater flows.

Hypoxia. A condition in which natural waters have a low concentration of dissolved oxygen (about 2 milligrams per liter as compared with a normal level of 8 to 10 milligrams per liter). Most game and commercial species of fish avoid waters that are Hypoxic.

I

Impaired. Water bodies that cannot reasonably be expected to attain or maintain applicable water quality standards, and at least one beneficial use shows some degree of degradation.

Industrial Wastes. Any solid, liquid, or gaseous wastes resulting from any process, or from excess energy of industry, manufacturing, trade, or business or from the development, processing, or recovery, except for agricultural crop raising of any natural resources.

Instantaneous Discharge. The discharge at a particular instant of time.

Intermittent Stream.A stream that carries water only part of the time, generally in response to periods of heavy runoff either from snowmelt or storms; a stream or part of a stream that flows only in direct response to precipitation. It receives little or no water from springs or other sources. It is dry for a large part of the year, generally more than three months. Flow generally occurs for several weeks or months in response to seasonal precipitation, due to groundwater discharge, in contrast to the Ephemeral Stream that flows but a few hours or days following a single storm. Also referred to as Seasonal Streams.

Interstate Waters. All waters which cross or form a part of the border between states.

Intrastate Waters. All waters of the state which are not interstate waters.

J

Jackson Turbidity Unit (JTU). The JTU is a measurement of the turbidity, or lack of transparency, of water. It is measured by lighting a candle under a cylindrical transparent glass tube and pouring a sample of water into the tube until an observer looking from the top of the tube cannot see the image of the candle flame. The number of JTUs varies inversely and non-linearily with the height of the sample (e.g., a sample which measures 2.3 cm has a turbidity of 1,000 JTUs whereas a sample measuring 72.9 cm has a turbidity of 25 JTUs).

L

Laboratory Blank. An artificial sample, usually distilled water, introduced to a chemical analyzer to observe the response of the instrument to a sample that does not contain the material being measured. The blank can also detect any contamination occurring during laboratory processing of the sample.

Land Application. An advanced physical, chemical and biological waste treatment process that uses soil, air, plants and bacteria to remove pollutants from wastewater. In this process, sewage is pretreated to screen and settle out large solids and then held in shallow lagoons to accelerate the action of bacteria. The sludge settles out and is applied to the land as fertilizer while the liquid (containing suspended and dissolved nutrients) is chlorinated (sewage) and sprayed on the land. Final purification is accomplished by natural biological, chemical and physical reactions in the soil.

Leachate. Liquid which has percolated through the ground, such as water seeping through a sanitary landfill, wastes, pesticides, or fertilizers. Leaching may occur in farming areas, feedlots, and landfills, and may result in hazardous substances entering surface water, ground water, or soil.

Leaching Requirements (LR). The fraction of the water entering the soil that must pass through the root zone in order to prevent soil salinity from exceeding a specified value. Leaching requirement is used primarily under steady-state or long-term average conditions.

Load. The amount of material that a transporting agency, such as a stream, a glacier, or the wind, is actually carrying at a given time. Also, the amount of power delivered to a given point. In this respect:
[1] Base Load = The minimum load in a stated period of time.
[2] Firm Load = That part of the system load which must be met on demand.
[3] Peak Load = Literally, the maximum load in a stated period of time. Sometimes the term peak load isused in a general sense to describe that portion of the load above the base load.

Load Allocation (LA). (Water Quality) The portion of the pollution Load of a stream attributable to human Non-Point Sources (NPS) of pollution. The amount of pollution from each point source is the Waste Load Allocation.

Lotic Waters. Describing the waters of rivers and streams (flowing waters) as compared to Lentic Waters of ponds or marshes (standing waters).

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Last Modified: 07/05/2007