Glossary

Glossary of Water Quality Terms

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Acidity

The term “acidity” refers to the capacity of water to resist a rise in pH, i.e., a decrease in H+ concentration, when it is mixed with bases. Acidity is measured by adding sodium hydroxide, NaOH, to a known volume of water until the pH increases to 8.0. The more NaOH required to raise the pH to 8.0, the greater the acidity of the water. Examples of sources of acidity in streams and lakes are acid mine drainage and acid rain. Related terms: pH, Alkalinity

Algae

Algae are one-celled plants that live in lakes and oceans. They live near the surface, where sunlight can penetrate. Algae are the foundation of food webs in aquatic ecosystems: They are eaten by microscopic animals called zooplankton, which are eaten by fish, which are eaten by larger fish, mammals, and birds. The growth of algae is limited by the availability of phosphporus and nitrogen nutrients. In freshwater lakes like the Finger Lakes, the limiting nutrient for algae growth is generally phosphorus. Related terms: Chlorophyll, nutrients, trophic status, Secchi depth

Alkalinity

The term “alkalinity” refers to the capacity of water to resist a drop in pH, i.e., an increase in H+ concentration, when it is mixed with acids. Alkalinity is measured by adding sulfuric acid, H₂SO₄, to a known volume of water until the pH decreases to 4.3. The more H₂SO₄ required to lower the pH to 4.3, the greater the alkalinity of the water. An example of a source of alkalinity in streams and lakes are underground limestone formations. Related terms: pH, Acidity

Ammonia

Ammonia, NH₃, is the major form of nitrogen present in animal and human waste. Ammonia is toxic to aquatic life. One of the principal functions of sewage treatment plants is to remove ammonia from wastewater before it is discharged to streams and lakes. Related terms: Nitrogen, Total Kjeldahl nitrogen, total nitrogen

Bacteria

One-celled organisms that are found virtually everywhere in nature, including water, soil and air as well as inside animals and plants. Bacteria are a class of microbes. Other microbes include viruses, fungi and parasites. The vast majority of microbes are harmless to humans, and some are beneficial. However, some microbes are capable of causing serious and even fatal diseases. Microbial diseases were much more common a hundred years ago than they are today. The birth of microbiology as a science in the 1870s and the improvements in sanitation that followed, for example, the purification of public drinking water and the construction of sewage treatment plants, are the main reason for the decrease in water-borne diseases such as cholera, typhoid and yellow fever. Vaccines and antimicrobial drugs have also played an important role in controlling microbial diseases. Indeed, when it comes to water, the main threats to human health are generally due to microbes. From a public health standpoint, the risk of chemical contamination is relatively small compared to the risk of microbial contamination, although when chemical contamination does ocur, for example, near a Superfund toxic waste site, it can constitute a serious publich health threat. The risk of microbial contamination is commonly assessed by testing for members of one large family of bacteria, the coliforms. Tests are generally not conducted for each of the many possible disease-causing microbes themselves, because that would take too much time and money. It would be like looking for the proverbial needle in a haystack. The microbes that are tested for, coliform bacteria, are not harmful (with the exception of a few rare strains). However, as concentrations of coliform bacteria rise, there is an increasing probability that disease-causing bacteria are also present in water. In other words, coliform bacteria are used as a risk indicator, a “red flag” for the potential presence of water-borne microbes that are capable of causing disease. Related terms: Total coliform, E. coli, fecal coliform

Chlorophyll

Chlorophyll is the green pigment in plants that captures the energy of photons in light and makes photosynthesis possible. Like other plants, one-celled algae contain chlorophyll. It is not easy to measure the concentration of algae themselves, and chlorophyll is commonly used as a surrogate measure of algae growth. Related terms: Algae, trophic status

Clean Water Act

The federal Clean Water Act was passed in 1972. Major provisions of the Act include requirements that states assign a “designated use” to every waterbody in their territory, for example, drinking water, contact recreation (swimming), or trout fishing; that states monitor water quality and restore impaired waterbodies to their designated uses; and that point sources of pollution, for example, sewage treatment plants, factories, and concentrated animal feedlot operations, be limited under SPDES (State Pollution Discharge Elimination System) permits as to the quantities of pollutants they are allowed to discharge to streams and lakes.Related terms: Rotating Intensive Basin Survey (RIBS), Standards, Priority Waterbodies List, Total Maximum Daily Load

Conductivity

Conductivity, also called specific conductance, measures the capacity of water to conduct an electrical current. It depends on the total concentration of positively and negatively charged molecules, or ions, that are dissolved in the water. Generally, ions come from underground minerals that dissolve in groundwater on its way to a stream. Because the water in runoff is generally “soft” water from rain or snowmelt, the conductivity of stream water usually decreases as the volume of water contributed by runoff to stream flow increases. Conductivity provides an indirect estimate of the concentration of total dissolved solids. Generally, total dissolved solids in units of mg/L is approximated by multiplying conductivity in units of µS (microsiemens)/cm by a factor of 0.7. For example, if conductivity is 300 µS/cm, then the concentration of total dissolved solids is approximately 210 mg/L. However, the actual concentration of total dissolved solids could range from 0.5 to 0.9 times the conductivity, or 150 to 270 mg/L, depending on the specific minerals dissolved in the stream water. Thus, conductivity provides only a rough estimate of total dissolved solids. Related terms: Total dissolved solids

Dissolved Oxygen

Fish and other aquatic creatures need oxygen to live, just like animals that live on land. Oxygen that is dissolved in water comes from the air and from photosynthesis by aquatic plants such as algae. Aquatic organisms breathe water through their gills, analogous to humans breathing air with our lungs. As water passes over gills, the dissolved oxygen in the water moves into the bloodstream and into the body’s cells, providing fuel for vital chemical reactions. Healthy waterbodies have dissolved oxygen concentrations ranging from around 12 mg/L at 4° C (40° F) to around 8 mg/L at 18° C (68° F). The difference is due to the physics of oxygen as a gas: The warmer the water, the more the oxygen tends to volatilize and move from the water into the surrounding air. Colder oxygen is less volatile, therefore more of it tends to stay in the water. Aquatic life generally need a minimum concentration of 3.5 mg/L of dissolved oxygen to survive. Oxygen can become depleted when water contains excessive amounts of organic matter. The reason is that when organic matter is decomposed by microorganisms, the decomposition process depends on biochemical reactions that require oxygen. Algal blooms in lakes and ponds offer a classic example of oxygen depletion. As algae die and large amounts sink to the bottom and are decomposed by microorganisms, dissolved oxygen levels drop. If dissolved oxygen falls too far, fish may begin to die. Oxygen levels rise again as the decomposition of the algae is completed and oxygen from the air replaces the dissolved oxygen that had been used up by the microbial decomposers. Related terms: Water quality standards, vital signs

E.coli

The intestines of humans and wildlife are home to large numbers of different kinds of bacteria, among them E. coli. With the exception of a few rare strains, E. coli are not harmful. Other intestinal microbes are more likely to cause disease. If significant concentrations of E. coli are present in water, they indicate that the water is contaminated by fecal matter and that there is a risk of infection from intestinal microbes. The higher the concentration of E. coli, the greater the risk of infection. Thus, E. coli serves as a risk indicator, a “red flag,” to warn of the risk of infection. The EPA considers an E. coli concentration up to 235 colonies (bacteria) per 100 ml of water to indicate an acceptable risk for contact recreation such as swimming. For drinking water, the acceptable concentration of E. coli is set at less than one colony per 100 ml of water. Related terms: Bacteria, fecal coliform, total coliform.

Fecal Coliform Bacteria

The test for fecal coliform bacteria is an older version of the E. coli test and serves the same purpose: To warn of contamination by fecal matter and serve as a “red flag” indicator of the risk of infection by intestinal microbes. A number of states, including New York, use the fecal coliform test rather than the E. coli test to regulate bacterial concentrations in water other than drinking water, for example, at swimming beaches and and in the water discharged from sewage treatment plants into streams and lakes. Fecal coliforms are a somewhat broader class of bacteria than E. coli. That is, all E. coli are fecal coliforms, but not all fecal coliforms are E. coli. When the fecal coliform test is used, a count of 200 colonies (bacteria) per 100 ml is considered to be the upper limit of acceptable risk for contact recreation such as swimming. The fecal coliform test is not used to regulate drinking water in New York State. Related terms: Bacteria, E. coliform, total coliform

Flow

The flow, which is also referred to as the discharge, is the volume of water moving down a stream per unit of time and is conventionally expressed in cubic feet per second (cfs or ft³/sec). Flow is measured in two parts: a) Using a current meter, the velocity of the water is measured in feet per second (ft/sec); and b) The cross-sectional area of the stream is measured in square feet (ft²) by determining the average width and depth at the point where the current velocity is measured. Flow is then calculated by multiplying the current velocity times the cross-sectional area of the stream:Flow (ft3/sec) = Velocity (ft/sec) x Cross-sectional area (ft²)Flow is a major determinant of water quality. In general, the higher the flow, the greater the concentrations of suspended sediment, phosphorus, bacteria and other pollutants. Of the total amount, or mass, of pollutants that enter Cayuga Lake from its tributary streams, roughly 90% enter when the flow is elevated due to rain or snowmelt.
Related terms: Groundwater, runoff, load

Groundwater

Approximately 96% of all freshwater on the planet is groundwater, while only 4% of freshwater is surface water in lakes and streams. Groundwater, like surface water, flows in a downhill direction under the influence of gravity, ultimately draining into a stream or lake. The underground path it takes depends on geological formations of soil, sand, clay, rocks and minerals. Groundwater sometimes collects in areas called aquifers, underground geological formations that are able to hold relatively large amounts of water. Groundwater is located in and among the soil, sand or other particles and minerals that make up the aquifer. Most of the water flowing in streams comes from groundwater most of the time. The kinds of minerals that are present in stream water are due to the specific kinds of underground minerals that groundwater comes in contact with, dissolving some of the underground minerals on its way to the stream. Groundwater may also contain chemicals and bacteria that are leached from the surface down into the ground by rainwater and snowmelt percolating down through the soil. Examples are nitrate from fertilizer and bacteria from liquid manure. Following heavy rain or snowmelt events, surface runoff may contribute a significant percentage of stream flow. Related terms: Watershed, runoff, flow, load

Load

The load is the total amount, or mass, of a chemical that is transported in stream water to a lake, estuary or other larger water body over a specified period of time. For example, load might be expressed as kilograms of phosphorus that are transported to Cayuga Lake by Fall Creek each day. Load is calculated as the product of two factors: a) The concentration of the chemical in stream water; and b) The flow of water in the stream:Load of chemical (kg/day) = Concentration of chemical (kg/m 3) x Flow (m³/day)

Nitrate

Nitrate, NO₃, is the form of nitrogen that plants take up from the environment as a nutrient. Nitrate may come from underground minerals that dissolve in groundwater as it flows to streams and lakes. Nitrate may also come from man-made fertilizers that are applied, for example, to agricultural fields, golf courses, and suburban lawns and enter streams and lakes in runoff when it rains. Related terms: Nitrite, nitrogen, total nitrogen

Nitrite

Nitrite, NO₂, is produced by bacteria in the environment and in the intestinal tract from nitrate, NO₃. Concentrations of nitrite are generally very low, and nitrite is rarely detectable in stream and lake water. The test for nitrate includes nitrite. Related terms: Nitrate, total nitrogen

Nitrogen

In addition to phosphorus, the other major nutrient determining plant and algae growth is nitrogen. Nitrogen comes in several chemical forms, including nitrate, organic nitrogen, and ammonia. is the form that plants take up from the environment is nitrate, NO₃. Nitrate is changed into organic nitrogen by being incorporated into biological molecules such as proteins and DNA. Waste from humans, mammals, fish and other creatures contains nitrogen in the form of ammonia, NH₃, as well as organic nitrogen. Because nitrate, ammonia and organic nitrogen differ chemically, they must be analyzed separately using methods suited to each of the different chemical forms. This is unlike phosphorus, which can be measured using a single method because it is readily converted to its basic chemical form, orthophosphate, PO₄. Related terms: Nitrate, ammonia, organic nitrogen, Total Kjeldahl nitrogen, total nitrogen, nutrients

Nutrients

Nutrients are basic chemicals that plants need in order to grow. The most important nutrients are phosphorus and nitrogen. In lakes, the availability of nutrients determines the growth of algae, one-celled plants near the surface of the water where sunlight can penetrate. Related terms: Algae, chlorophyll, trophic status

Organic Nitrogen

See Total Kjeldahl Nitrogen

pH

The term “pH” refers to the concentration of hydrogen ions, H⁺, in water. The higher the concentration of H⁺, the lower the pH. The lower the concentration of H+, the higher the pH. The reason is that pH is the negative logarithm of the H⁺ concentration. For example, if the H⁺ concentration is 10^-2 moles/liter, the pH is 2. If the H⁺ concentration is 10^-9 moles/liter, the pH is 9. Because pH is a logarithmic scale, a change of 1 pH unit means the H⁺ concentration changes by a factor of 10. For example, when the pH changes from 2 to 3, the H⁺ concentration decreases from 10^-2 moles/liter to 10^-3 moles/liter. A pH of 7 (H⁺ concentration of 10^-7 moles/liter) is defined as being a neutral pH. Water with a pH less than 7 is described as “acidic,” while water with a pH greater than 7 is described as “basic” or “alkaline.” Note that when the terms “acidic” and “alkaline” are used as general descriptions of pH being less than or greater than pH 7, they are not the same as the “acidity” and “alkalinity” of water. “Acidity” and”alkalinity” do not describe pH, rather they define the capacity of water to resist changes in pH. Related terms: Algae, trophic status, turbidity

Phosphorus

In addition to nitrogen, the second major nutrient driving the growth of algae and other aquatic plants is phosphorus. The chemical form of phosphorus that is taken up by plants as a nutrient from the environment is orthophosphate, PO₄. Orthophosphate is incorporated into DNA, ATP, and other molecules essential to life. Related terms: Total phosphorus, soluble reactive phosphorus, trophic status

Priority Waterbodies List

When RIBS results indicate that a waterbody’s designated use has or is threatened to become impaired, the waterbody is placed on the NYSDEC’s Priority Waterbodies List (PWL) and evaluated for remediation. Allocation of limited resources to restore a waterbody to its designated use depends on the nature and severity of the problem, the economic importance of the waterbody, and the feasibility of remedial action. States report impaired waterbodies to the EPA every two years in the so-called 303d report, named after the section in the Clean Water Act requiring states to provide biannual reports of waterbody impairments. The EPA may impose a remedial action plan if it concludes that the state is not doing enough to restore a waterbody to its designated use. Related terms: Clean Water Act, water quality, Standards, Total Maximum Daily Load, Rotating Intensive Basin Survey

Rotating Intensive Basin Survey (RIBS)

RIBS is the water quality monitoring program of the New York State Department of Environmental Conservation (NYSDEC) that complies with the federal Clean Water Act requirement to monitor waterbodies and protect their designated uses. The RIBS program divides New York State into 17 major drainage basins. Approximately two to three basins are monitored each year; thus, each basin is monitored roughly once every six to eight years. Given limited resources, DEC staff sample a few percent of the waterbodies in each drainage basin, targeting resources on waterbodies suspected of water quality problems. Results are published annually in the so-called 305b report, named after the section of the federal Clean Water Act requiring states to provide annual reports of water quality. Related terms: Clean Water Act, water quality, Priority Waterbodies List, Standards, Total Maximum Daily Load

Runoff

Runoff is water from rain or snowmelt that does not percolate into the ground and become groundwater but instead flows along the surface to a depth of a few inches. Because it does not percolate into the ground, runoff bypasses the filtering action of soil and deposits into the nearest water body eroding soil particles and debris as well as chemicals and bacteria that may be present at or close to the surface. Runoff reflects local land uses and has a significant impact on water quality. A variety of factors increase the volume of runoff and the concentrations of sediment, bacteria and chemicals that reach streams and lakes: Lack of vegetation holding soil in place, impermeable surfaces such as roads and parking lots, inadequate municipal stormwater systems, leaky on-site septic systems, agricultural fertilizers and pesticides, and road salt, to name a few. Controlling runoff is one of the main goals of land use planning as it relates to water resource management. Related terms: Turbidity, bacteria, nutrients, load, trophic status
Secchi depth is determined for lakes using a secchi disk: A round disk with alternating white and black quadrants. The secchi disk is lowered over the side of a boat. The depth at which the disk just disappears from sight is the secchi depth. Secchi depth depends on algae growth: The more algae, the shallower the Secchi depth. Secchi depth is inversely related to turbidity.
Related terms: Algae, trophic status, turbidity

Secchi depth

Several streams and lakes in Tompkins County were placed on New York State’s Priority Waterbodies List in the last RIBS survey published for our drainage basin, the Seneca-Oswego-Oneida River basin, in 1996, including Six Mile Creek, lower Fall Creek, Cascadilla Creek. The southern end of Cayuga Lake was placed on the EPA’s 303d list in 2005. A common feature of federal plans to remediate water quality is the Total Maximum Daily Load, or TMDL. The TMDL is the maximum amount, or load, of a pollutant that is permitted to be transported by a stream each day. Examples of pollutants that may be regulated by TMDLs are sediment, phosphorus and nitrogen. The TMDL is controversial as an enforcement tool. Its usefulness depends on correctly identifying problem chemicals, accurately measuring their amounts, and successfully designing strategies to reduce their presence in the stream. TMDL requirements could be imposed on streams in Tompkins County as part of a comprehensive strategy for remediating the southern end of the Cayuga Lake. Citizen involvement is envisioned by the Clean Water Act as an integral part of safeguarding water resources. It is virtually impossible, even with more tax revenues and bigger budgets than are available today, for any State to monitor all of its waterbodies often enough to identify problems early so they can manage them before they become expensive to fix. In fact, when conducting a RIBS survey of a major drainage basin every five to seven years, the DEC asks local agencies to point out streams and lakes that they think should be checked. In general, local, state and federal government agencies in New York welcome volunteer monitoring data as an important aid in monitoring water resources. Click to view: Volunteer Monitoring Pilot Projects. Following is an overview of New York State classifications of waterbodies together with water quality standards and guidelines.

Class A

Class A Drinking, cooking, contact recreation (swimming), fishing, fish propagation and survival
(aquatic life).
Class B Primary and secondary contact recreation, fishing, fish propagation and survival (aquatic life).
Class C Fishing, fish propagation and survival (aquatic life). Can be suitable for contact recreation,
but may be limited.
Class D Fishing. Cannot support fish propagation due to natural conditions such as streambed and
flow. Suitable for fish survival. Contact recreation may be limited.

Soluble Reactive Phosphorus

This test measures phosphorus that is dissolved and “free” in water. Phosphorus in microorganisms or attached to soil particles is excluded by passing the water sample through a filter with a 0.45 micrometer pore size (a micrometer is a millionth of a meter or a thousandth of a millimeter). The filter retains microorganisms and other particulates but lets the dissolved phosphorus pass through. Soluble reactive phosphorus is “bioavailable” to algae and other plants, which means that they can take it up as a nutrient directly from the environment. Related terms: Phosphorus, total phosphorus, trophic status

Standards

Water quality standards are based on the designated use of a waterbody. For example, water quality standards are different for a lake that serves as a source of drinking water than for a stream that supports fish reproduction but is not potable or swimmable. The table below gives an overview of water quality standards for New York State. Some standards are expressed as numerical limits while others are expressed as verbal statements. Guidelines are offered when no standard is available. Note that the “classification” of a waterbody means the same as “designated use.” Related terms: Clean Water Act, water quality, Total Maximum Daily Load, Rotating Intensive Basin Survey, Priority Waterbodies List

Temperature

Water temperature has a big impact on the health of fish and other aquatic organisms. Trees and shrubs growing along the banks of a stream provide shade and help keep stream water cool. This “riparian buffer zone” may be eliminated when land is developed, for example, for a suburban housing tract, a commercial farm, or a golf course. As stream water is no longer shaded, temperatures rise, endangering aquatic species that require cool temperatures, such as trout. Another effect of warmer water is an increase in the growth of bacteria and other microbes, including pathogenic (disease-causing) species. Related terms: Water quality standards, vital signs

Total Coliform Bacteria

Total coliforms are a much broader class of bacteria than fecal coliforms. In addition to the intestines of humans and wildlife, coliform bacteria live virtually everywhere in the environment, including in soil and in streams and lakes. Total coliforms are rarely harmful. Their presence, like that of E. coli and fecal coliform bacteria, serves as a general “red flag” indicator of the risk of infection by other, pathogenic microbes. The test for total coliform bacteria is not used to regulate potentially contaminated water such as swimming areas or sewage treatment plant outfalls. Rather, it is used as general guide to water quality in sgtreams and lakes. The New York State Department of Environmental Conservation recommends 2,400 total coliform colonies per 100 ml as an upper limit in ambient waters. For drinking water, total coliforms are used in addition to E. coli as a “red flag” indicator of infection risk. As for E. coli, the acceptable concentration of total coliform bacteria is set at less than one colony per 100 ml of drinking water. In other words, public drinking water supplies are required by law to have less than one colony of total coliform bacteria and less than one colony of E. coli bacteria per 100 ml in order to be considered safe to drink. Related terms: Bacteria, E. coli, fecal coliform

Total Dissolved Solids

Under base flow conditions, the water in a stream or a lake comes mostly from groundwater. Dissolved solids are primarily minerals that groundwater leaches from rocks and soil as it flows underground. To measure dissolved solids, a dish is dried and weighed, the water sample is filtered to remove any suspended solids, a known volume of the filtered sample is added to the dish and evaporated, and the dish is dried and weighed again. The difference between the before and after weights gives the concentration of total dissolved solids. Dissolved solids are a general indication of the concentration of minerals in the water. “Hard” water has higher concentrations of dissolved minerals, for example, calcium carbonate, while concentrations are lower in “soft” water from rain and snowmelt. Because dissolved minerals are responsible for the electrical conductivity of water, electrical conductivity can be used to obtain a rough estimate of the concentration of total dissolved solids. The mass of total dissolved solids is almost always greater than the mass of total suspended solids, even when water is very turbid.Related terms: Conductivity

Total Kjeldahl Nitrogen

Organic nitrogen is found in plants and animals in the form of proteins, DNA and other large molecules essential to life. There is no direct test to measure organic nitrogen. Total Kjeldahl nitrogen (TKN) measures the sum of organic nitrogen plus ammonia. Ammonia can then be measured separately and subtracted from TKN to obtain organic nitrogen. Because TKN is the sum of ammonia plus organic nitrogen, it serves as a useful indicator of water quality impacts due to human and animal waste. Related terms: Nitrogen, ammonia, total nitrogen

Total Maximum Daily Load

The total maximum daily load, or TMDL, is the maximum amount, or mass, of a pollutant that may be transported by a stream to a specific location in one day. TMDLs are enforcement tools that are incorporated into remedial action plans designed to restore waterbodies to their designated uses. TMDLs may require local governments in a watershed to take action to reduce pollutant discharges from businesses and private property owners. Related terms: Clean Water Act, water quality, Standards, Rotating Intensive Basin Survey, Priority Waterbodies List

Total Nitrogen

Total nitrogen refers to the total amount of nitrogen present in a water sample, regardless of the chemical form the nitrogen is in. Total nitrogen is calculated as the sum of nitrate plus TKN. Total nitrogen indicates the total amount of this nutrient that is available or potentially available to support algae growth and impact the trophic status of lakes, estuaries and other water bodies. Related terms: Nitrogen, nitrate, ammonia, Total Kjeldahl nitrogen

Total Phosphorus

The total phosphorus test measures all the phosphorus in a water sample, including soluble reactive phosphorus (dissolved or “free” phosphorus), phosphorus attached to soil particles, phosphorus in organic waste, and phosphorus in microorganisms such as algae. The sample is first boiled in acid and ammonium persulfate, a strong oxidizing agent, in order to release the diverse forms of phosphorus and make them available for measurement. Total phosphorus is always equal to or greater than soluble reactive phosphorus; how much greater depends on the concentration of suspended sediment, organic waste and other particulate sources of phosphorus in the water. Related terms: Phosphorus, soluble reactive phosphorus, trophic status

Total Solids

Total solids are the sum of total dissolved solids and total suspended solids. Total solids are measured by drying and weighing a dish, adding a known volume of a water sample, and drying and weighing the dish again. The difference between the before and after weights gives the concentration of total solids. Related terms: Total dissolved solids, total suspended solids

Total Suspended Solids

There are two major sources of suspended solids in streams. First, runoff, the water that flows over the ground following a rain or snowmelt, picks up dirt and soil particles from many different places such as construction sites, eroding stream banks, suburban parking lots, agricultural fields and city streets. When runoff is not controlled, it carries these solids into the nearest stream or lake together with any chemicals it picks up along the way. Streams themselves are the second major source of suspended solids. When water flows swiftly, it scours the stream bottom, lifting mud, sand, pebbles, rocks and even small boulders and carrying them downstream. Suspended solids, especially fine soil particles in runoff, can endanger aquatic life by coating the stream bottom and making it unfit for the small animals and insects fish depend on for food. Suspended solids can clog gills, causing suffocation. Suspended solids also absorb heat from the sun, raising the temperature of the surrounding water and causing thermal stress. Suspended solids are measured by drying and weighing a filter, passing the water sample through the filter in order to trap suspended solids on it, then drying and weighing the filter again. The difference between the “before” and “after” weight of the filter gives the concentration of suspended solids. Related terms: Turbidity, Secchi depth

Trophic Status

The ability of a lake to produce and support life is referred to as its trophic state. “Trophic” comes from the Greek word for “grow”. Three broad trophic states are used to classify freshwater lakes: Oligotrophic, or low productivity; mesotrophic, or intermediate productivity; and eutrophic, or high productivity. A eutrophic state is considered undesirable for a number of reasons, including excessive growth of algae and other aquatic plants, hypoxia (reduced oxygen) and resulting fish kills, and diminished recreational and aesthetic value. Three indicators are used to assess a lake’s trophic state: Chlorophyll, a measure of algae concentration; phosphorus, the limiting nutrient for algae growth; and secchi depth, a measure of water clarity. Trophic status indicators for oligotrophic, mesotrophic and eutrophic lakes are listed below. Cayuga Lake is considered to be a mesotrophic lake. Related terms: chlorophyll, soluble reactive phosphorus, Secchi depth

Turbidity

Turbidity is due to fine particles of solid material that are suspended in water. Two synonyms for “turbid” are “cloudy” and “opaque.” Turbidity in stream water is typically caused by suspended soil and dust particles in runoff that washes into the stream following a rain or snowmelt. Turbidity in lake water, by contrast, is typically caused by the growth of microscopic algae near the surface. Turbidity is measured by shining a beam of light on a sample of water and determining the intensity of the light that is scattered at a 90º angle. There is a close correlation between turbidity and total suspended solids. Related terms: Total Suspended Solids, Secchi depth

Water Quality

Water quality refers to the physical, chemical and bacteriological composition of water that makes it suitable as a habitat for aquatic life and a source of drinking water and recreational enjoyment for human populations. Water quality is assessed by measuring specific physical, chemical and bacteriological parameters (characteristics). Water quality is regulated under state and federal laws which set standards and guidelines for water quality parameters. Related terms: Standards, Clean Water Act, Rotating Intensive Basin Survey (RIBS), Priority Waterbodies List (PWL),Total Maximum Daily Load

Watershed

A watershed is the land that water is in contact with as it moves, under the influence of gravity, toward a surface water body such as a stream or a lake. Most of the water in a watershed is underground, in the form of groundwater. Following rain or snowmelt, surface runoff is added to groundwater, and runoff can comprise a significant proportion of the water reaching a stream. Groundwater and runoff determine water quality in streams and lakes. Water quality is a direct reflection of the hydrogeology of groundwater and land uses in a watershed. Another term for watershed is drainage area. Related terms: Drainage area, flow, load