ECMI Glossary of Water Related Terms

Absorption is the process by which chemicals in gaseous, liquid or solid phases are incorporated into and included within another gas, liquid, or solid chemical. For example, sponges absorb water.

Acceptable daily intake (ADI) is the chemical ingestion level determined by combining the maximum No-Observed-Adverse-Effect-Level (NOAEL) with the addition of an uncertainty (safety) factor. Chemicals with ADI levels usually are not considered or suspected to be carcinogens. This classification results from toxicity data collected during prolonged ingestion studies conducted on a number of animals.

Acidity -The base neutralizing capacity of a water is known as acidity. Acids contribute to corrosiveness, influence chemical reactions, and chemical/biological processes. Acidity is determined using a titrametric or potentiometric method.

Acre-foot is the volume of water (325,851 gallons of water) required to cover one acre of land with 12 inches of water.

Adsorption is the adherence of gas molecules, ions or solutions to the surface of solids. For example, odors from freezers and refrigerators are adsorbed to baking soda.

Advection is the process by which chemicals and heat are transported along with the bulk motion of flowing gas or liquid. For example, nitrates move through soils and aquifer formations due predominantly to the bulk motion or movement of water.

Alkalinity: The acid neutralizing capacity of a water is known as alkalinity. For surface waters alkalinity has been called "The Protector of the Stream", since the alkalinity of the water rests sudden changes in the pH of the stream associated with the influx of acid deposition, water containing organic acids, groundwater discharges or industrial wastes.

Most surface waters have alkalinity’s < 200 mg CaCO3/L, but in limestone areas the alkalinity’s can be greater than 1000 mg CaCO3/L. In some cases, pristine surface water have very low alkalinity’s and therefore they would be adversely impacted by acid mine drainage and acid rain. The alkalinity of precipitation can be from 1 to about 10 mg CaCO3/L. Typically the best alkalinity for aquatic life is between 100 and 120 mg CaCO3/L. Alkalinity is determined using a titrametric or potentiometric method.

Aluminum(Al): There is no published Maximum Contaminant Level (MCL), but 0.2 mg/L is considered safe. Elevated aluminum is believed to be associated with forms of dementia, such as: Alzheimer’s.

Ammonia (NH4): There is no MCL established for ammonia. Ammonia is very toxic to fish and aquatic life. Ammonia concentrations of 0.06 mg/L can cause gill damage in fish and 0.2 mg/L is lethal to trout. Concentrations in excess of 0.1 mg/L suggest domestic or agricultural sources of waste.

Anion is a negatively charged chemical. Nitrate and chloride (Cl^-) are examples of anions.

Anion exchange is the chemical process where negative ions of one chemical are preferentially replaced by negative ions of another chemical. In water treatment, the net effect is the removal of an unwanted ion from a water supply. For example, some municipalities are installing anion exchange systems to remove nitrate from their water supplies.

Antimony (Sb): The maximum contaminant level is 0.006 mg/L. Elevated levels of antimony can increase blood cholesterol and decrease blood glucose.

Aquifer is the saturated underground formation that will yield usable amounts of water to a well or spring. The formation could be sand, gravel, limestone or sandstone. The water in an aquifer is called groundwater. A saturated formation that will not yield water in usable quantities is called an aquiclude. Most Pennsylvania aquifers may be categorized into confined and unconfined aquifers.

• Confined aquifer (artesian aquifer) is the saturated formation between low permeability layers that restrict movement of water vertically into or out of the saturated formation. Water is confined under pressure similar to water in a pipeline. Drilling a well into this type of aquifer is analogous to puncturing a pressurized pipeline. In some areas confined aquifers produce water without pumps (flowing artesian well). When pumping from confined aquifers, water levels often change rapidly over large areas. However, water levels will generally recover to normal when pumping ceases.

• Unconfined aquifer (water table aquifer) is the saturated formation in which the upper surface fluctuates with addition or subtraction of water. The upper surface of an unconfined aquifer is called the water table. Water, contained in an unconfined aquifer, is free to move laterally in response to differences in the water table elevations.

Arsenic (As): The MCL for arsenic is 0.05 mg/L. Arsenic is highly toxic and its prevalence is due to the natural occurrence of this metal and past use of arsenic in pesticides. Arsenic poisoning typically makes people feel tired and depressed and this poisoning is also associated with weight loss, nausea, hair loss, and marked by white lines across your toenails and fingernails. For freshwater the concentration should be less than 0.05 mg/L.

Artificial recharge is the unnatural addition of surface waters to groundwater. Recharge could result from reservoirs, storage basins, leaky canals, direct injection of water into an aquifer, or by spreading water over a large land surface.

Barium (Ba):The MCL is 2 mg/L. Barium can increase blood pressure.

Beryllium (Be): The MCL is 0.004 mg/L and it can cause intestinal lesions.

Baseflow is that part of streamflow derived from groundwater flowing into a stream.

Biological Oxygen Demand (BOD) : BOD is typically reported as 5 day BOD and ultimate BOD at 20 C and reported as milligrams of oxygen consumed per liter (mg O/L). BOD 5 is used by regulatory agencies for monitoring wastewater treatment facilities and monitoring surface water quality. BOD is the biochemical oxygen demand of the water and it is related to the concentration of the bacterial facilitated decomposable organic material in the water. A sample with a 5 day BOD between 1 and 2 mg O/L indicates a very clean water, 3.0 to 5.0 mg O/L indicates a moderately clean water and > 5 mg O/L indicates a nearby pollution source. BOD is a laboratory test that requires a oxygen sensing meter, incubator, nitrifying inhibitors, and a source of bacteria.

Cadmium (Cd): The MCL for cadmium is 0.01 mg/L. Cadmium poisoning is associated with kidney disease and hypertension and possibly mutations. For freshwater the concentration should be less than 0.0004 mg/L.

Calcium (Ca): No specific recommendation, but high calcium is associated with hardness, total dissolved solids problems and can cause aesthetic problems.

Capillary fringe is a zone of partially saturated material just above the water table. The depth of the fringe depends upon the size and distribution of the pore spaces within the geologic formation.

Cation is a positively charged chemical. For example, calcium (Ca⁺²), and Magnesium (Mg⁺²) are cations.

Cation exchange is a process where positively charged ions of one chemical are preferentially replaced by positive ions of another chemical. For example, water softeners replace Ca⁺², and Mg⁺² ions with the sodium (Na⁺²) ion.

Chloride (Cl): It is one of the major anions found in water and wastewater. The recommended maximum contaminant level is 250 mg/L, since the chloride ion imparts a salty taste to the water. If ions of Calcium and Magnesium are present, the chloride ion may not impart a salty taste until over 1000 mg/L. In addition to human and animal waste, sources of chloride can include natural geological formations, road salt storage and applications, oil / natural base drilling, and saltwater intrusions. High levels of chloride can attack and weaken metallic piping and fixtures and inhibit the growth of vegetation. Chloride ion is detected using a titrametric or potentiometric method.

Chlorine: Chlorine in one of a number of forms is added to water to destroy or deactivate disease-causing microorganisms and is the mostly widely used disinfectant in the United States. Elevated chlorine levels can great aesthetic problems (strong taste and odor) and if organic matter is present it can result in the creation of trihalomethanes, which are potentially carcinogenic with target organs including the liver and kidney.

Chemical Oxygen Demand (COD): COD is used as a measure of the oxygen equivalent of the organic matter content of the sample. Only the organic matter that is susceptible to oxidation by strong chemical oxidant. COD is typically used when there are industrial wastewater sources, comparing biological to chemical oxidation in the selection of treatment process and performances, or depending on the waste stream it can provide insight into the concentration of reduced inorganic metal inorganic, such as ferrous iron, sulfide, and manganese. Chromium (Cr): The MCL is 0.05 mg/L. The impact of chromium is not clearly defined, but it is known to adversely impact aquatic organisms.

Conductivity:The theoretical definition of conductivity is the "reciprocal of the resistance of a cube of a substance 1 cm on a side at a specified temperature". Typically the units of measure are microhms/cm (uohms/cm) or microsiemens/cm (uS/cm). Conductivity or specific conductance is a measure of the ability of a fluid to carry a charge which is directly related to the concentration of dissolved substances. As the total dissolved substances in the water increases, the conductivity of the water also increases. For More information see Total Dissolved Solids.

Cone of depression is a depression in groundwater levels around a well in response to groundwater withdrawal or pumping water.

Contaminant is any unnatural biological, chemical, physical, or radiological substance or matter contained in water. Tri-chloroethylene (TCE) is a synthetic cleaning solvent sometimes found in groundwater near manufacturing sites.

Copper (Cu): The MCL is 1 mg/L. At 1 mg/L, the water may taste bitter and is highly toxic and may disrupt the metabolic processes, especially for children. For freshwater the concentration should be less than 0.036 mg/L.

Deep percolation is the movement of water below the maximum effective plant root zone.

Denitrifying Bacteria: In the process of nitrification of wastewater, the two key bacteria of ecological importance are nitrosomonas and nitrobacteria. These bacteria facilitate "catalyze" the reactions. Nitrosomonas results in the removal of three pairs of electrons from ammonia facilitating the formation of nitrite and nitrobacteria removes to electrons from nitrite to form nitrate. The bacteria responsible for denitrification are autotrophic and heterotrophic facultative anaerobes. Monitoring for denitrifying bacteria is typically done to monitor the performance of denitrification systems.

Diffusion is a process where heat or chemicals are transported in response to differences in chemical concentration or temperature. Movement is from high concentration (or temperature) to low concentration (or temperature). This process could involve liquids, gases and solids.

Discharge area is an area where groundwater moves toward or is delivered to the soil surface. Groundwater can flow into springs, or seeps; contribute baseflow to streams; or provide supplemental water for plant use.

Dispersion is the process whereby a chemical, contained in water, deviates from the path that would be expected due to bulk flow. In the process the chemical is mixed with surrounding liquids, causing its concentration to be reduced.

Distillation is a two-stage water treatment method: 1) the liquid is boiled, producing water vapor; 2) the water vapor is condensed, leaving most contaminants behind. Distillation can be used to remove inorganic chemicals, some non-volatile organic chemicals, and bacteria.

Drawdown is a lowering of the groundwater surface caused by withdrawal or pumping of water from a well. It is the difference between the static water level and the pumping water level in a well pumped at a constant flow rate.

Drainage is the process of transporting surface water over a land area to a river, lake or ocean (surface drainage), or removal of water from a soil using buried pipelines that are regularly spaced and perforated (subsurface drainage).

Effluent is the discharge of a contaminant or contaminants with water from animal production or industrial facilities or waste water treatment plant.

Erosion is the process or series of processes that removes soils, crop residues, and organic matter from the land surface in runoff waters, or by wind. Water droplets begin the erosion process by detaching soil particles. Runoff waters transport the detached particles to local and regional streams or lakes. Soil erosion represents the single largest source of nonpoint pollution in the United States.

Eutrophication is the process of surface water nutrient enrichment causing a water body to fill with aquatic plants and algae. The increase in plant life reduces the oxygen content of the water. Eutrophic lakes often are undesirable for recreation and may not support normal fish populations.

Evapotranspiration (ET) is the process of changing soil water into water vapor through the combination of soil evaporation and plant water use, or transpiration.

Field capacity is the amount of water a soil contains after rapid drainage has ceased. It is the water content following a period of gravity drainage without the addition of water.

Fecal coliform is a portion of the coliform bacteria group originating in the intestinal tract of warm-blooded animals that pass into the environment as feces. Fecal coliform often is used as an indicator of the bacteriological safety of a domestic water supply.

The fecal coliform bacterial densities will be determined using the membrane filtration technique. The MF procedure uses an enriched lactose medium and an incubation temperature of 44.5 + 0.2oC. Fecal coliform is bacteria typically found in the feces of warm blooded mammals. Fecal coliform colonies produced by the M-FC medium are blue, while non-coliform colonies are pale yellow, gray, or cream color. Since fecal coliform is found in mammalian waste, it is recommended that fecal coliform be absent from potable water.

Fecal Streptococcus:The fecal streptococcus group consists of a number of species of the genus Streptococcus, such as: S. faecalis, S. faecium, S. avium, S. bovis, S. equinus, and S. gallinarum. Fecal Streptococci are typically found in the gastrointestinal tract of warm blooded animals. Due to the variation in survival rates the ratio of FC/FS should not be used as a means of differentiating human and animal sources of bacterial contamination. Fecal streptococcus colonies produced by the KF-Streptococcus broth are red. For potable water, the fecal streptococcus should be absent.

Gaining stream (effluent stream) is a stream or portion of a stream where flow increases because of discharge from groundwater.

Grains per gallon is a unit of measurement often used to describe water hardness. One grain per gallon is approximately equal to 17 ppm of various cations.

Groundwater (sometimes written as two words) is water that occupies voids, cracks, or other spaces between particles of clay, silt, sand, gravel or rock within the saturated formation.

Groundwater mining is the removal of groundwater from an aquifer in excess of the rate of natural or artificial recharge. Continued groundwater mining reduces the groundwater supply until it is no longer an economical source of water.

Groundwater recharge is the process where water enters the soil and eventually reaches the saturated zone. Recharge varies from place to place due to the amount of rainfall, infiltration, and surface vegetation.

Hardness: The hardness of a water is a measure of the concentration of the multivalent cations (positively charged particles) in the water, but primarily it is equivalent to the calcium and magnesium concentration of the water. Hardness is typically reported as mg /L as CaCO3 (calcium carbonate), but it may also be reported as grains per gallon (1 gpg (US) = 17.12 mg CaCO3/L ). Hardness Classification: Soft: 0 to 17 mg CaCO3/L; Slightly Hard: 17 to 60 mg/L; Moderately Hard 60 to 120 mg/L; Hard 120 to 180 mg/L; and Very Hard > 180 mg/L. For more information visit the Hardness Website.

Health advisory level (HAL) is a non-regulatory health-based chemical concentration in drinking water that results in no adverse health risks when a given amount of water is ingested over exposure periods ranging from one day to a lifetime.

Heterotrophic Bacteria: Heterotrophic plate count is a procedure for estimating the number of live heterotrophic bacteria in the water. Colonies may form in pairs, colonies, clusters or single cells, which can be termed as "colony-forming units". The colonies are relatively small/compact and do not encroach on each other. This procedure can accommodate volumes of sample or diluted < 1.0 ml. Test is typically performed in high purity water, pilot treatment facility performance evaluations, and pilot scale testing.

Hydraulic conductivity is a term used to describe the ease with which water moves through soil or a saturated geologic material. Hydraulic conductivity is influenced by the type of material comprising the formation (sand, gravel, rock, limestone, sandstone, clay), the slope of the water table, the type of fluid, and the degree to which existing pores are interconnected.

Hydraulic gradient is the slope of the water surface in an aquifer. The hydraulic gradient indicates the direction groundwater will flow. Water always flows from higher water table elevations to lower water table elevations. All other factors being equal, flow is greater when the hydraulic gradient is steeper.

Hydrologic cycle describes the constant movement of water above, on, and below the earth's surface. Processes such as precipitation, evaporation, condensation, infiltration and runoff comprise the cycle. Within the cycle, water changes forms in response to the Earth's climatic conditions.

Infiltration is the downward entry of water into the soil. The infiltration rate is a function of surface wetness soil texture, surface residue cover, irrigation application or precipitation rate, surface topography and other factors.

Iron (Fe):The MCL is 0.3 mg/L. Iron is a secondary drinking water standard and primarily regulated because of the aesthetic problems associated with elevated iron concentrations.

No Available Definitions

No Available Definitions

Leaching is the removal of dissolved chemicals from soil by the movement of a liquid (like water).

Lead (Pb):The MCL is 0.05 mg/L. Symptoms of lead poisoning start as: abdominal pains, constipation, fatigue, depressed appetite and decrease endurance, but long-term exposure may led to nerve and kidney damage and anemia.

Losing stream (influent stream) is a stream or portion of a stream that discharges water into the groundwater.

Low permeability layers include soil, sediment or other geologic material that inhibit water movement. These layers may serve as a base material, or confining beds for an aquifer. This may be caused by a fragipan or silt clay horizon in the soil.

Magnesium (Mg): No specific recommendation, but high calcium is associated with hardness, total dissolved solids problems and can cause aesthetic problems.

Manganese (Mn):The MCL is 0.05 mg/L. Manganese is primarily regulated because of the aesthetic problems associated with elevated levels of manganese, i.e., a secondary drinking water standard. Elevated manganese levels can disrupt the nervous system and regeneration of hemoglobin. For freshwater the concentration should be less than 1.5 mg/L.

Maximum contaminant levels (MCLs) are legally enforceable drinking water standards required by the Safe Drinking Water Act. Standards set by the Environmental Protection Agency establish the maximum permissible concentration of selected contaminants in public water supplies. Contaminants are included on the list if they pose a public health risk. For example, 10 ppm is the MCL for nitrate-nitrogen (NO³-N).

Maximum contaminant level goals (MCLGs) are public drinking water standards that serve as nonenforceable goals for selected contaminants contained in drinking water that pose no health risk to people over a lifetime of exposure. A MCLG is a suggested level set by EPA as a guideline for water utilities.

Mecury (Hg): The MCL is 0.002 mg/L for organic mercury. Mercury has been associated with kidney disease. For freshwater the concentration should be less than 0.00005 mg/L.

Methemoglobinemia or blue baby syndrome is the condition that limits the oxygen-carrying capacity of red blood cells. The condition occurs when bacteria in the digestive tract convert nitrate to nitrite. Nitrite reacts with hemoglobin in the blood, producing methemoglobin which cannot carry oxygen. The resulting oxygen starvation causes a bluish discoloration of the body. The condition is largely confined to infants less than 9 months old. Excessive amounts of nitrates may be ingested with water or food. Often foods, such as fresh vegetables, are a major source of nitrates.

Nickel (Ni): MCL has not been established, but for freshwater the concentration should be less than 0.1 mg/L. Element detected using flame atomic absorption, no specific standard for nickel. Nickel may cause dermatitis and nasal irritation.

Non-point source (NPS) pollution is the source of surface or groundwater pollution originating from diffuse areas without well-defined sources. The most common examples of NPS are chemicals that enter surface water during runoff events from crop land and turfgrass, and soil erosion from cultivated cropland and construction sites.

Ozone - A form of oxygen, O3. A powerful oxidizing agent that is considered a pollutant in the lower troposphere but an essential chemical in the stratosphere where it protects the earth from high-energy ultraviolet radiation from the sun.

Ozone Disinfection - (see link)

Part-per-million (ppm) is a measure of concentration of a dissolved material in terms of a mass ratio (milligrams per kilogram, mg/kg). One part of a contaminant is present for each million parts of water. For water analysis, parts per million often is presented as a mass per unit volume (milligrams per liter, mg/l). There are one million milligrams of water in one liter.

Perched water tables occur when a low permeability material, located above the water table, blocks or intercepts the downward flow of water from the land surface. Water mounds up above the impermeable material, creating another saturated zone with a water table.

Permeability is the property of porous materials indicating the ease with which liquids or gases will be transmitted through a soil or other porous material. Permeabilities are not affected by changing the type of liquid.

pH is a numerical measure of the acidity or alkalinity of water. The pH scale ranges from 1 (acidic) to 14 (alkaline). A pH of 7 is neutral.The technical definition of pH is that it is a measure of the activity of the hydrogen ion (H+) and is reported as the reciprocal of the logarithm of the hydrogen ion activity. Therefore, a water with a pH of 7 has 10-7 moles per liter of hydrogen ions; whereas, a pH of 6 is 10-6 moles per liter. The pH scale ranges from 0 to 14. For more information please visit the pH Website.

Phosphate (PO4): There is no MCL for phosphate. In surface waters, phosphate is typically a limiting plant nutrient. The recommend maximum concentration in rivers and streams is a concentration of 0.1 mg/L of total phosphate.

Point-of-entry (POE) treatment is the treatment of all water entering a house, farmstead or other facility, regardless of its intended use. Anion exchange is an example of POE treatment to remove nitrates.

Point-of-use (POU) treatment is treatment of water at the point it is used. A common example would be water treatment at the kitchen sink for drinking and cooking uses. Reverse osmosis, distillation and ozone are examples of POU treatment methods.

Point source (PS) pollution is the source of surface or groundwater pollution that originates from a well-defined source. Examples include: industrial effluent; large animal containment facilities; city waste water treatment discharges; or chemical spills. Point sources commonly are associated with pipeline discharges of some type.

Pollutant is any unwanted chemical or change in physical property that renders a water supply unfit for its intended use.

Porosity is the ratio of the volume of open spaces or voids to the total volume of a porous material. For example, a sand and gravel deposit may have 20 percent porosity. Porosity determines the amount of water that can be stored in a saturated formation. A saturated formation 100 feet thick with a porosity of 20 percent could store an equivalent water depth of approximately 20 feet.

Potable water supply is a source of water that can be used for human consumption.

Precipitation is the process where water vapor condenses in the atmosphere to form water droplets that fall to the earth as rain, sleet, snow or hail. Nebraska's long-term annual precipitation varies from 16 inches in the west to 34 inches in the southeast. Annual deviations can be greater than 30 percent.

Pumping water level is the water level in a well when the pump is operating and water is being removed.

No Available Definitions

Recharge area is the area where water predominantly flows downward through the unsaturated formation (zone) to become groundwater.

Reference dose (RfD) is the maximum daily exposure to a chemical that is judged to be without risk of adverse systemic health effects over a person's lifetime. It formerly was called the Acceptable Daily Intake.

Reverse osmosis (RO) is a water treatment method used to remove dissolved inorganic chemicals and suspended particulate matter from a water supply. Water, under pressure, is forced through a semipermeable membrane that removes molecules larger than the pores of the membrane. Large molecules are flushed into waste waters. Smaller molecules are removed by an activated carbon filter.

Runoff is precipitation or irrigation water that does not infiltrate but flows over the land surface toward a surface drain, eventually making its way to a river, lake or an ocean.

Saturated formation (zone) is the portion of a soil profile or geologic formation where all voids, spaces or cracks are filled with water. No air is present. There may be multiple water-bearing formations within a saturated formation. These water-bearing formations often are separated by layers of clay or other impermeable layers.

Saturated thickness (zone) is the total thickness of a saturated formation.

Seepage is the movement of water into or through a porous material. Seepage occurs from canals, ditches, and other water storage facilities. It sometimes is used to describe water escaping from municipal landfill sites.

Selenium (Se):The MCL is 0.05 mg/L. Selenium is associated with hair or fingernail loss, numbness of fingers and toes, and circulatory problems. For freshwater the concentration should be less than 1.5 mg/L.

Shock chlorination is the addition of chlorine for disinfecting a water supply system including the well, and all distribution pipelines. Shock chlorination is recommended when coliform bacteria are detected, or after system repairs. Treated water, with a concentration of at least 200 ppm, is pumped throughout the distribution system and allowed to set for at least 24 hours before flushing with untreated water.

Silver (Ag):The MCL is 0.10 mg/L. Silver is associated with causing discoloration of the skin. For freshwater the concentration should be less than 0.0003 mg/L.

Sodium (Na):No MCL has been set. For individuals on low sodium diets a general recommendation of 20 mg/L is used.

Specific capacity expresses the productivity of a well. Specific capacity is obtained by dividing the well discharge rate by the well drawdown while pumping.

Specific yield is the ratio of the volume of water that will drain from a unit volume of aquifer by gravity flow.

Spring is the point of natural groundwater discharge to a soil surface, river, or lake.

Static water level is the water level in a well located in an unconfined aquifer when the pump is not operating. The static water level is the surface of the water-bearing formation and typically is synonymous with the water table.

Strontium (Sr):No MCL has been set, but the element is analyzed using nitrous oxide -acetylene flame. The primary concern is the presence of a radioactive form, known as Strontium-90.

Sulfate (SO4):The drinking water limit is 250 mg/L. Sulfate (SO4-2) is widely distributed in natural waters, but is typically less than a few mg/L. In Northeastern Pennsylvania, the primary sources of sulfate in surface waters and groundwater include: acid mine drainage, acid deposition, and mineral oxidation. Standard set because of taste and aesthetic problems and sulfates laxative effects.

Sulfite (SO3):May occur in boilers and boiler feedwaters treated with sulfite to control dissolved oxygen levels, natural waters containing industrial waste and in wastewater treatment plant effluents using sulfur dioxide to dechlorinate the effluent.

Thallium (TI): The MCL is 0.002 mg/L, but a MCL Goal is 0.0005. Thallium is associated with hair loss, changes in the blood, and kidney, digestive, and liver problems.

Tin (Sn):No MCL has been established for tin.

Total Kjeldahl Nitrogen (TKN): There is no MCl for total kjeldahl nitrogen. This parameter is used to measure the total amount of organic nitrogen and is typically used for surface water and groundwater investigations associated with domestic or agricultural contamination.

Transmissivity is the capacity of an aquifer to transmit water. It is dependent on the water-transmitting characteristics of the saturated formation (hydraulic conductivity) and the saturated thickness. For example, sand and gravel formations typically have greater hydraulic conductivities than sandstone formations. The sand and gravel will have a greater transmissivity if both formations are the same thickness.

Total dissolved solids (TDS) is a water quality parameter defining the concentration of dissolved organic and inorganic chemicals in water. After suspended solids are filtered from water and water is evaporated, dissolved solids are the remaining residue. Dissolved solids commonly found in Nebraska water are calcium, magnesium, sodium, potassium, bicarbonate, sulfate, chloride and silica. Total dissolved solid concentrations depend on the geologic material water passes through in the saturated and unsaturated zone, and the quality of the infiltrating water. Total dissolved solid contents range from less that 100 ppm in the Small streams to greater than 1,000 ppm near the Susquehanna River in northeast Pennsylvania.

Turbidity: Turdidity is a measure of the cloudiness or opaqueness of the water and is measured in nephelometric turbidity units (ntu). The turbidity is influenced by the amount and nature of suspended organic and inorganic material in water. Typically, the higher the concentration of the suspended material the greater the turbidity. The value of 1 ntu is recommend for drinking water, since higher turbidities could cause aesthetic problems or inhibit the ability of a system to disinfect the water. The source of turbidity could be fine sand, silt, and clay (i.e., soil separates); organic material, particles of iron and manganese or other metal oxides, rust from corroding piping, or carbonate precipitates. Turbidity measurements are typically not made on surfacewater sources - see Total suspended solids.

Total Solids: The total amount of solids in the sample, which includes: dissolved, suspended, and volatile.

Total Suspended Solids: A fixed volume of sample is filtered through a preweighed and washed glass fiber filter. The filter is then rinsed and dried at 103 to 105 C. The change in the weight of the filter represents the weight of suspended material. This test is typically done for surfacewater supplies and wastewater treatment plants. For drinking water, turbidity is parameter that is typically monitored.

Total Dissolved Solids: Is determined by filtering a measured volume of sample through a standard glass fiber filter. The filtrate (i.e., filtered liquid) is then evaporated to dryness at a constant temperature of 180 C. High total dissolved solids may effect the aesthetic quality of the water, interfere with washing clothes and corroding plumbing fixtures. For aesthetic reasons, a limit of 500 mg dissolved solids/L is typically recommended for potable water supplies.

Total Volatile Solids: The residue for previous testing is then ignited at a temperature of 500 C. The change in the weight represents the amount of suspended or dissolved solids that are organic in nature or volatilized. The parameter is typically used in wastewater treatment plants because it provides an estimate of the organic matter content within the waste stream.

Unsaturated formation (vadose zone) is the soil or other geologic material usually located between the land surface and a saturated formation where the voids, spaces or cracks are filled with a combination of air and water.

Vanadium (V):Currently there is no specific MCL for vanadium. Vanadium may cause respiratory problems and inhibition of Na and K in ATP production.

Watersheds are regional basins drained by or contributing water to a particular point, stream, river, lake or ocean. Watersheds range in size from a few acres to large areas of the country.

Water table is the upper level of a saturated formation where the water is at atmospheric pressure. The water table is the upper surface of an unconfined aquifer.

No Available Definitions

Yeast and Molds: Yeast and molds are fungi. A fungus is a colorless (i.e., lacking chlorophyll) plant with practically no differentiation of cell structure. Yeast are small single-celled forms that reproduce by budding or spore formation. Molds produce spores for both asexual and sexual reproduction. Yeast and mold analysis is typically done on air-borne samples and surface wipes.

Zinc (Zn): The MCL is 5 mg/L, because of problems with the aesthetic quality due to the taste of zinc.