Oregon Water Science Center Glossary | U.S. Geological Survey

A

Acoustic velocity meter

A device that uses sound waves to track velocity of particles moving in the water column.

Akinetes

Dormant cells found in some species of cyanobacteria. These cells enable phototrophic bacteria to endure harsh and starvation conditions.

Aphanizomenon

A type of cyanobacteria or blue-green algae commonly found in freshwater phytoplankton assemblages. In nutrient-rich waterbodies it can form dense blooms.

B

BOD5

BOD5 refers to the five-day biochemical oxygen demand of bacteria and microorganisms decomposing nitrogenous and carbonaceous matter in water.

Backwater

Water backed up in its course by an obstruction (such as a dam), an opposing current, or the tide.

C

CBOD

Oxygen demand of bacteria and microorganisms decomposing carbonaceous matter in water.

CE-QUAL-W2

A water quality and hydrodynamic model in 2D (longitudinal-vertical) for rivers, estuaries, lakes, reservoirs and river basin systems. W2 models basic eutrophication processes such as temperature-nutrient-algae-dissolved oxygen-organic matter and sediment relationships.

Coagulant

A substance that causes a liquid to thicken or clump

Cyanobacteria

Also known as blue-green algae, these photosynthetic bacteria naturally inhabit freshwater ecosystems. However, an excess of nutrients in warm water can create conditions that cause cyanobacterial blooms that can produce toxins. These blooms often appear as floating mats of foul-smelling, decaying, scum in lakes and can also form mats on the bottoms of streams.

Cyanotoxins

Cyanotoxins are produced by cyanobacteria, also known as blue-green algae, found in freshwater, estuarine, and marine waters. Once these toxins are released, they can cause numerous health effects ranging from minimal (i.e., diarrhea, headaches, and skin irritation) to life threatening (i.e., death).

D

Diatoms

Diatoms are the base of the food chain in aquatic ecosystems. Any of a class (Bacillariophyceae) of minute planktonic unicellular or colonial algae with silicified skeletons that form diatomite.

Dolichospermum

A type of cyanobacteria genus that is commonly found in freshwater phytoplankton assemblages. In nutrient-rich waterbodies it can form dense blooms.

E

Eutrophic

A body of water that is rich in dissolved nutrients.

Evapotranspiration

The process by which water is transferred from the land to the atmosphere, by water leaving the soil (evaporation) and water lost through plant leaves and stems (transpiration).

G

Gage height

The height of the water surface above the gage datum (zero point). Gage height is often used interchangeably with the more general term, stage, although gage height is more appropriate when used with a gage reading.

Geomorphic

landform evolution

Groundwater

Liquid water stored underground, within rocks of all kinds, stored in cracks and in the pore spaces of sediments and sedimentary rocks. Groundwater can be fresh, saline, or brackish. The term “aquifer” refers to rocks that can hold substantial amounts of water.

Groundwater discharge

Processes through which water leaves a groundwater system. Examples: water resurfaces naturally in springs, lakes, rivers and other water bodies, and from plants consuming water through roots. Human caused discharge occurs from withdrawals through wells.

Groundwater recharge

Processes through which water can enter a groundwater system. Examples: rain and snowmelt infiltration, seepage from water bodies such as lakes, rivers, etc.

H

High-head dams

A dam that stores water at a higher elevation for better power generation.

Hydraulic modeling

Hydraulic modeling simulates and analyzes the behavior of water flow in various systems, such as rivers, channels, pipelines, or stormwater networks.

Hypereutrophic

Extremely rich in nutrients.

I

Impoundments

A body of water formed by a dam.

Isotope

Isotopes are atoms of the same element with different numbers of neutrons. For example, carbon always has 6 protons, or else it wouldn't be carbon. Carbon 12 has 6 protons and 6 neutrons to equal carbon 12. An isotope of carbon - carbon 14 still has 6 protons but has 8 neutrons to equal 14.

L

Lidar

Light Detection and Ranging (LiDAR) systems use lasers to measure the elevation of objects on the ground, in forests, under water and even in buildings.

M

Macroinvertebrates

Small organisms without a backbone that are visible to the naked eye. The most common in aquatic systems, living in water as nymphs or larvae at least until they reach their adult stages. Common types include dragonflies, caddisflies, stoneflies, beetles, midges, and mayflies.

Mesocosm

An outdoor environment that is designed to determine the effects that different changes have on an ecosystem.

Microcystin

A potent liver toxin and possible human carcinogen. Cyanotoxins can also kill livestock and pets that drink affected waters.

Microcystis

A genus of cyanobacteria commonly found in freshwater phytoplankton communities. In nutrient-rich waterbodies, it can form dense blooms.

O

Organochlorine pesticides

Organochlorine pesticides are chlorinated hydrocarbons used extensively from the 1940s through the 1960s in agriculture and mosquito control. As neurotoxicants, many organochlorine pesticides were banned in the United States, although a few are still registered for use in this country.

Oscillatoria

A type of cyanobacteria or blue-green algae commonly found in freshwater. Its name refers to the oscillating movement of its filaments as they slide against each other, positioning the colony to face a light source.

P

Per- and polyfluoroalkyl substances

PFAS are a group of synthetic chemicals used in a wide variety of common applications, from the linings of fast-food boxes and non-stick cookware to fire-fighting foams and other purposes. Their persistence in the environment and occurrence across the country make them a unique water quality concern.

Periphyton

A plant assemblage including microbial communities of algae and cyanobacteria living attached to submerged aquatic vegetation.

Permeability

Describes the ability of groundwater to flow through rocks or sediments.

Photosynthesis

Photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy. During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds.

Phreatophytes

A deep-rooted plant that obtains its water from near the water table. Phreatophytes often have their roots in constant contact with groundwater.

Polybrominated Diphenyl Ethers

PBDEs belong to a class of chemicals that are added to certain manufactured products in order to reduce the chances that the products will catch on fire. Finished products that may contain PBDEs are furniture foam padding; wire insulation; rugs, draperies, and upholstery; and plastic cabinets for televisions, personal computers, and small appliances.

Polychlorinated biphenyls

PCBs belong to a broad family of man-made organic chemicals known as chlorinated hydrocarbons. PCBs were domestically manufactured from 1929 until manufacturing was banned in 1979. PCBs may be present in products and materials produced before the 1979 PCB ban.

Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a group of over 100 different chemicals that are formed during the incomplete burning of coal, oil and gas, garbage, or other organic substances like tobacco or charbroiled meat.

Pumpage

The amount of liquid raised by pumping.

S

Suspended sediment

Suspended sediment is primarily fine particles of clay and silt. It also may include fine sand and particles of organic matter suspended in the water column.

T

Turbidity

The measure of relative clarity of a liquid. Turbidity is an optical characteristic of water and is a measurement of the amount of light that is scattered by materials in the water.

W

Water year

The 12-month period October 1, for any given year through September 30, of the following year. Commonly used in hydrology to describe the time period for which precipitation totals are measured.