Can’t find a term here? Try the USGS’s Glossary of Hydrologic Terms
Ammonia is a byproduct of human and animal waste, and also is a common substance found in industrial waste. Ammonia can be toxic to fish and other aquatic life at certain concentrations.
Benthic Macroinvertebrates are animals without backbones that are larger than ½ millimeter (the size of a pencil dot). These animals live on rocks, logs, sediment, debris and aquatic plants during some period in their life. Benthic macroinvertebrates include crustaceans such as crayfish, mollusks such as clams and snails, aquatic worms and the immature forms of aquatic insects such as stonefly and mayfly nymphs.
Conductivity is a measure of how well water passes an electrical current. Conductivity is an indirect measure of dissolved solids, such as sodium, iron, nitrates or phosphates in the water. Pure water is not a good conductor of electricity - only water with dissolved solids in it, such as salts or metals, can conduct electricity.
Dissolved Oxygen (DO) is a measure of the amount of oxygen dissolved in the water. It comes in the form of tiny bubbles of oxygen mixed in with water molecules. Dissolved oxygen is critical to aquatic life such as fish and macroinvertebrates. Dissolved oxygen varies with depth, velocity and temperature of the water. It is also affected by bacteria, which use oxygen to decompose organic matter in the water.
E. coli is a subset of fecal coliform and includes a broad group of bacteria with many strains, some of which can cause illness in humans. E. coli is monitored in surface waters as an additional, more effective, indicator of pathogens in the water. It is currently being used as a standard for recreational use of surface waters in Colorado.
Eutrophication is the response in water due to overenrichment by nutrients, primarily phosphorus and nitrogen, and can occur under natural or manmade (anthropogenic) conditions. `Manmade' eutrophication, in the absence of control measures, proceeds at an accelerated rate compared to the natural phenomenon and is one of the main forms of water pollution. The resultant increase in fertility in affected lakes and slow-flowing rivers causes symptoms such as algal blooms, heavy growth of rooted aquatic plants (macrophytes), algal mats, deoxygenation and, in some cases, unpleasant odor, which often affects most of the vital uses of the water such as water supply, recreation, fisheries (both commercial and recreational), or aesthetics.
Fecal coliform is a broad family of bacteria that is monitored in surface waters. Fecal coliform comes from the intestines of animals and humans, and may indicate the presence of pathogens in the water.
Habitat is the place where a population lives. A population is a group of living organisms of the same kind living in the same place at the same time. Several populations may share a habitat. Habitats vary in size. A habitat must supply the needs of organisms, such as food, water, temperature, oxygen, and minerals. If the population's needs are not met, it will move to a better habitat.
Indicator Bacteria are used to monitor the presence of disease-causing organisms (pathogens) in surface waters. Two types of indicator bacteria are fecal coliform and E. coli, which are sometimes referred to as BacT or Bacteria.
Nitrate is a nitrogen compound that is used in fertilizers. It also comes from human waste, industrial wastewater, and car exhaust. It is a type of nutrient that can spur excessive algae growth in a lake or stream. Nitrates have also been found to be a cause of Blue Baby Syndrome.
Non-point source is a discharge that does not have one specific source, such as a factory. Non-point source pollution comes from the cumulative effect of a region's residents going about their everyday activities, such as fertilizing a lawn or driving a car.
Nutrients are substances such as nitrogen and phosphorous which are necessary to living things for basic life processes. Aquatic plants and algae need a certain amount of nutrients to survive, but an overabundance of nutrients can promote excessive algae growth and accelerate the natural process of eutrophication.
Phosphorus is a natural element found in rocks, soils and organic material and is a nutrient required by all organisms for the basic processes of life. Phosphorus clings tightly to soil particles and is used by plants, so its concentration in clean waters is generally very low. However, phosphorus is used extensively in fertilizers and other chemicals, so it can be found in higher concentrations in areas of human activity. In freshwater lakes and rivers, phosphorus is often found to be the growth-limiting nutrient, because it occurs in the least amount relative to the needs of plants. If excessive amounts of phosphorus and nitrogen are added to the water, algae and aquatic plants can be produced in large quantities.
Phosphate is a phosphorus compound that is a type of nutrient. Orthophosphate is the most stable kind of phosphate, and is the form used by plants. Orthophosphate is produced by natural processes and is found in sewage. It comes primarily from detergents and fertilizers, and can also spur excessive algae growth.
pH is a measure of the acidity or baseness of water. It is based on a scale of 0 to 14, with 7 being neutral. Values below 7 are acidic, and values above 7 are basic. The scale is logarithmic, meaning each whole number on the scale is 10 times more acidic or basic than the preceding one. For example, a pH of 4 is 100 times more acidic than a pH of 6. pH can vary normally in a body of water from 6 to 9. When waters are too acidic or basic, they become harmful to aquatic life.
Point source is a discharge from a single source, such as a factory or wastewater treatment plant. In 1970, Congress passed the Clean Water Act, which put restrictions on how much and what kind of pollutants industries can dispose of in rivers and lakes. While this has not eliminated industrial or domestic waste from entering our waters completely, it has reduced what once was our biggest pollution threat.
Riparian areas are the green, vegetated areas on each side of streams and rivers. They serve many important functions, including purifying water by removing sediments and other contaminants; reducing the risk of flooding and associated damage; reducing stream channel and streambank erosion; increasing available water and stream flow duration by holding water in stream banks and aquifers; supporting a diversity of plant and wildlife species; maintaining a habitat for healthy fish populations; providing water, forage, and shade for wildlife and livestock; and creating opportunities for recreationists to fish, camp, picnic, and enjoy other activities.
Stormwater Outfalls are locations where water in storm sewers discharges into a river or lake.
Temperature is an important factor for aquatic life. It affects metabolic rate, and affects the activity level of bacteria. It also has an influence on dissolved oxygen level (colder water has higher dissolved oxygen levels).
Turbidity is a measure of how cloudy the water is. It is caused by suspended solids in the water, such as organic material, silt and microorganisms. Turbidity is measured using a device called a secchi disc, which is lowered into the water until it is no longer visible. The depth at which the sechi disappears is then recorded.
Volatile Organic Compounds (VOCs) are compounds containing carbon that readily evaporate. VOCs come from fuel spills, industrial sites, some household products, and combustion engines.
The Water Column is a vertical section of the water in any surface water body.
Can’t find a term here? Try the USGS’s Glossary of Hydrologic Terms.