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Water Quality Terms


Lakes are a limited, non-renewable resource. They are especially sensitive to human disturbance because they act as collecting basins for all the water which flows from the lands which surround them. As rainfall and snowmelt wash across the land’s surface, these forces lift loose soil, carry it along, and finally deposit it in tributary streams and lakes. This is harmful because every soil particle carries with it a nutrient for plants called phosphorus. When it gets into a lake, phosphorus feeds microscopic floating organisms called algae or cyanobacteria. If too much phosphorus is added, algal populations explode and lake water becomes cloudy, smelly, and uninviting.

Watershed - An area of land that drains water, sediment and dissolved materials to a common receiving body or outlet. The term is not restricted to surface water runoff and includes interactions with subsurface water. Watersheds vary from the largest river basins to just acres or less in size. In our area the relevant watershed is approximately 180 square miles that include parts of 13 communities, seven major lakes and several smaller water bodies. The outlet is the head of Messalonskee stream. To protect and preserve our lakes we must pay attention to the entire Belgrade Watershed: all lands and all waters.

Phosphorus loading refers to all processes which carry phosphorous to the lakes and streams of the watershed. In a state of nature, lakes remain sparkling and clear for tens or even hundreds of thousands of years because trees, grasses and bushes protect them from soil erosion and phosphorus loading. Human development speeds rainwater runoff and increases phosphorus loading by exposing soil, removing native cover, leveling the ground and covering it with non-absorbent surfaces like buildings, roads, and parking lots.

Water clarity is diminished as algae and cyanobacteria prosper from the long term increase in phosphorous. Clarity is expressed as “Secchi depth” which is the depth at which a special disc becomes invisible below the water surface. Long Pond’s long-term decrease has caused the State to design a program to control phosphorous loading.

Gloeotrichia echinulata is an organism that forms tiny clusters in the lake water. It has been seen in our lakes at least since 1987, but wasn’t particularly noticeable until 2002. Since then, occasional phosphorus gushes have promoted episodes of Gloeotrichia overgrowth that collect on the surface as a green scum called a bloom.

Algae and blue-green algae are outdated names for the group of organisms to which Gloeotrichia belongs: properly called cyanobacteria. Scientists recently changed the name to reflect new knowledge. However, the old terms are still often used. Please see “GLOEOTRICHIA Frequently Asked Questions

Remediation refers to fighting the blooms and water quality decline. The fight requires new funds. Remediation may target long term, widespread effects or localized, short term impacts. We have many long term programs underway already. The Belgrade Lakes Association advocates landscaping that filters rainwater and road maintenance that prevents runoff. We support the LakeSmart program for homeowners who want to learn how to improve lake water quality please review our  Lake Smart  page  or call  the Conservation Corps which provides labor for runoff abatement (call 495-6039). Two localized, short term methods: ultrasound and on-shore pumping are scheduled for Test Trials this summer. Ultrasound ideally will use the energy of high frequency sound waves to kill scum organisms with little or no other effects. Pumping will remove scum from surface water and deposit it in uninhabited lake shore areas.
For news, stay tuned to the Belgrade Lakes Association website,

Alkalinity    Alkalinity is the capacity of water to neutralize acid. Often confused with pH,  which is a measure of the strength of an acid or base, alkalinity is a measure of the ability  of a solution to resist changes in pH. Alkalinity is therefore a measure of the solution's  buffering capacity and is measured in molar equivalents per cubic meter, or, equivalently,  milli equivalents per liter [meqll]. It is frequently expressed as equivalent mg/I CaCOa.  In natural waters, alkalinity is essentially equal to the sum of the molar quantities of  carbonate [cC$], bicarbonate [HCO)"), and hydroxyl [mions. In some situations,  berates [BOI"~],silicates[~i0i2],and phosphates poi3], [HPO,'~],rH2P04>can also  contribute to alkalinity.

The main source of alkalinity in natural waters is dissolution of carbonate rocks  such as limestone. As a result, streams in limestone regions tend to have high alkalinity  and are resistant to changes in pH. Consequently, these streams are better able to buffer  the stresses of acid rain than non-ztlkahe mountain lakes in granitic regions.  Maintenance of pH within a water body is important for fish and other aquatic organisms.  If pH is lowered due to acid rain, it can also increase leaching of heavy metals from  sediments leading to higher dissolved metal contaminant levels.

Alkalinity is typically measured in the laboratory by titration after converting the  carbonate and bicarbonate to carbonic acid by lowering the pH, Samples collected for  alkalinity tests should be refrigerated and processed within 24 hours of collection.

Carbon Dioxide    Carbon dioxide (CO;) is a colorless, odorless gas that is produced during respiration by plants, animals, and bacteria, as well as through combustion of carbon-   based fuels. During the daytime,plants consume CO; during photosynthesis of carbon- based organic compounds,with oxygen generated as a byproduct  This leads to a diurnal cycle in both carbon dioxide and oxygen, which will be discussed more thoroughly under    "Oxygen." In this cycle, carbon dioxide is lowest in the daytime and highest at night, when there is no photosynthesis and aquatic organisms (including plants) are producing    additional CQ2through respiration.

Carbon dioxide plays an important role in the carbonate system that controls the    pH of natural waters. Although comprising only about .03% of the atmosphere at sea    level, COa is highly soluble in water and solubility increases as temperature decreases. In    solution, aqueous C02reacts with water to form carbonic acid (HaCOs),which    dissociates in two steps, first to bicarbonate and then to carbonate. The FT1' ion released    during these dissociation slowers the pH;so high COa levels will lead to lower pH.    These dissociations are reversible,equilibrium processes, so high levels of bicarbonate    and carbonate ions will allow higher levels of COa to exist at equilibrium, resisting the    change in pH as discussed under "Alkalinity." This influence on pH means that as COa    and oxygen levels cycle diurnally, pH also cycles inversely with the CO;.    Carbon dioxide can be measured in the laboratory by titration.It is typically not  routinely measured in surface water quality studies because of the rapid equilibration of    the carbonate system and high solubility of atmospheric carbon dioxide. Instead, levels  can be calculated from pH and alkalinity measurements.

Conductivity    Conductivity is a measure of the ability of the water to pass an electrical current.  While pure distilled water is a very poor conductor, as inorganic ionic solids dissolve in  water (e-g., Nad), adding positively charged cations (e.g., ~a4)and negatively charged  anions (e. g., CF), conductivity of fhe solution increases. Organic compounds such as oils  or alcohols do not dissociate when they dissolve and do not increase conductivity.  Conductivity increases with ionic strength and temperature and is generally reported as  conductivity at 25'C. In practice, electrical conductance (conductivity of 1 cm3),is  measured using two platinum electrodes to determine resistance,which is the inverse of  conductance. Conductivity is measured in micromhos (pnho) or,equivalently,  microsiemens (ps) per centimeter. Distilled water has a value of approximately 1p/cm,  whereas typical streams and rivers, can range from 50 to 1500 ps/cm. Readings in the  range of 150 to 500 p/cm are considered healthy for good mixed fisheries.

Conductivity is useful as a general measure of stream water quality and it is an  easy measurement to make. Streams tend to have a relatively constant range of  conductivity that is the result of the makeup of the bedrock through which they flow as  well as steady-state discharges. Once the normal range is established, significant changes  from this baseline can be an indicator of a change in a discharge or addition of some other pollutant in(he stream. Inorganic pollutants such as road salt or sewage discharges  will increase conductivity while organic contaminants such a soil will lower conductivity.

Conductivity is typically measured in the field with a probe or meter but can also  be measured in the lab on collected samples. It is important to use thoroughly cleaned  (phosphate-free detergent) and rinsed (distilled water) glass or polyethylene bottles for  these samples.

Fecal Colifonn Bacteria    The presence of pathogens (i.e., those organisms capable of infecting or    transmitting diseases to humans) is a primary concern in recreational waters and waters    used for drinking water supply. Because it is difficult to test for some pathogens, and    because there are so many different species of pathogenic organisms,fecal colifonn, fecal    streptococcus,and total colifornn are used as indicator species. High colifonn    concentration indicates poor bacteriological water quality, which implies possible    elevated pathogen levels. Fecal colifornn, like pathogens, are ubiquitous in nature.    Sources of fecal colifornn and fecal streptococci include animal waste (wild animals,    livestock, and manure) and human waste (septic system leach or leaking sewage    pipes). It is interesting to note that fecal colifonn multiply in the environment,while    fecal streptococci do not multiply in water. In addition to the possible health risk    associated with elevated levels of fecal bacteria, they can also cause cloudy water,    unpleasant odors, and increased biological oxygen demand. The federal and state surface water quality criterion for fecal colifonn for contact recreation is 200 cfa/100ml (i.e.,    colony forming units per 100ml sample).

Studies conducted by EPA (USEPA 1997) to determine the correlation between    different bacterial indicators and the occurrence of digestive system illness at swimming    beaches suggest that the best indicators of health risk from recreational water contact in  fresh water are E. coil (a specific coliform species) and enterococci (a sub-group of the  fecal streptococci). For salt water, enterococci are the best indicator as these bacteria  survive in salt water while most other fecal bacteria do not. Interestingly, fecal coliforms  as a group were determined to be a poor indicator of the risk of digestive system illness,  However, many states, including Pennsylvania, continue to use fecal colifoms as their  primary health risk indicator.

Bacteria can be difficult to sample and analyze. Background levels can vary  significantly and are strongly correlated with rainfall. As a result, wet and dry weather  bacteria data can sometimes vary by orders of magnitude. It is important to note weather  conditions when collecting samples. Sterile conditions are required to collect and handle  samples. Samples collected should be collected directly in the sterile container and  should include sterile field blanks and field duplicates. Samples must be refrigerated and  processed within six hours of collection.

Nitrates    Nitrogen is a complex element that can exist in many forms. From awater quality  perspective, the compounds of most interest are organic nitrogen (nitrogen contained in  organic matter), ammonia (NHs); nitrite (NOa") nitrate (NO;); urea [CO(NI&)2];and  nitrogen gas (N;). Total Kjeldahl Nitrogen (TKN) is a measure of the organic nitrogen  plus the ammonia nitrogen. In nature, nitrogen continually cycles between these various  forms. While nitrogen gas comprises over 70%of the atmosphere, only a few plants and  some bacteria can directly fix nitrogen gas to form organic compounds containing  nitrogen. Most plants can use nitrates and or ammonia to build proteins,while all  animals must use organic nitrogen obtained from consuming plants or animals.

This leads to a complex cycle in which atmospheric nitrogen is converted to  organic nitrogen(proteins)by nitrogen fixers (or to nitrates through lightning). Organic  nitrogen is broken down through bacterial action to urea and ammonia. Nitrifying  bacteria oxidize ammonia to nitrites and then to nitrates than can be used by plants, while  denitnfying bacteria reduce these compounds to elemental nitrogen that returns to the  atmosphere. hi addition,man has developed various processes to convert atmospheric  nitrogen or inorganic mineral forms to ammonia-ornitrate-containing fertilizers and  large quantities of nitrates are produced as a result of combustion of fossil .fuels.  Atmospheric deposition of these combustion byproducts can be significant in urban areas  such as Philadelphia. Other sources of nitrates include waste water treatment plants,  runoff from fertilized lawns and croplands, failing septic systems, run off from animal  manure storage areas, and industrial discharges that contain corrosion inhibitors.

While nitrates are necessary for aquatic plant growth that supports a healthy  ecosystem, excess nitrates, in combination with phosphates, can lead to eutrophic  conditions inwhich excessive plant and algae growth occurs. The algae may reduce the  amount of sunlight reaching rooted vegetation. In addition, the increased plant activity  causes fluctuations in dissolved oxygen levels and pH, and some algal blooms may be  toxic to aquatic life. Furthermore, when the algae die and begin decomposing, they can  seriously deplete the surrounding water of oxygen in addition to causing taste and odor  problems. The dead algae matter will also form bottom deposits, thereby decreasing the  water depth.

Nad levels of nitrates during the growing season are typically low (less than 1  ma) although sewage treatment effluent can range up to around 30 mgA. The surface  water quality standard for nitrogen in Pennsylvania is that nitrate plus nitrate cannot  exceed 10 mg/1measured as nitrogen (PA Code Section 25, Chapter 93).

Typical methods for analyzing nitrates and nitrites include colorimetric analysis  with a spectrophotomet~or color wheel following reduction with cadmium, or the we of  a nitrate electrode. These measurements can be done in the field with variow test kits  such as those supplied by Hach. Samples collected for laboratory analysis should be  refrigerated and kept in the dark to retard metabolism and processed within 48 hours.  Preservation with sulfuric acid is recommended.

Oxygen and Biochemical Oxygen Demand (BOD)    The dissolved oxygen (DO) level is one of the most basic indicators of a water  body's ability to support aquatic flora and fauna. Oxygen becomes dissolved in water through diffwion from the atmosphere, fmbulmt mixing from &g water and  entrainment of bubbles, and production by plants as a result of photosynthesis. Swiftly  flowing water will have a higher DO than stagnant water due to the fact that the water is  aerated more efficiently as it mixes and flows. From a physical chemistry standpoint,  saturated DO concentrations increase as water temperature decreases. In a thriving  ecosystem, however, there are large diurnal (i.e., daily) fluctuations of DO during the  growing period. As the number of plants and algae increase, so does the amount of  photosynthetic activity, resulting in elevated DO levels during the daylight hows. As the  sun goes down and photosynthesis ceases, the DO concentration will decrease as a result  of plant and animal respiration throughout the nighttime.

A major source of oxygen depletion in the water column and sediments is the    microbial decay of organic matter such as dead plants and animals. The amount of    oxygen consumed by these microbial organisms in breaking down dissolved and solid    organic wastes is known as biochemical oxygen demand, or BOD. Sources of oxygen-   consuming waste include waste water treatment plants, storm water runoff from farmland,    urban streets, and failing septic systems, as well as dead plant and algae material.    In contrast to lakes and ponds where oxygen levels tend to vary with depth, DO in    well-mixed rivers and streams changes more in the horizontal along the course of the    waterway as conditions change. For example, BOD loading from a waste water treatment    plant can lower oxygen levels immediately below the outfall. These levels will tend to    recover as the water moves downstream and undergoes reaeration, resulting in a so-called    'oxygen sag" curve. Conversely, waterfalls and riffles can significantly increase levels from immediately upstream pools or impoundments.

In Pennsylvania, TSF (Trout Stocking Fishery) streams such as the Wissahickon  Creek must meet Dissolved Oxygen Standard Do5 (PA Code Section 25, Chapter 93).    This requires minimum ddy average DO ofat least 6.0 mgA, with an absolute minimum    of 5.0mg/1 for the period Feb 15 to July 3 1 and requires the 24-hour average DO to    remain above 5.0 mg/1 and DO to be above 4.0 mgfl at all times for the remainder of the    year.

In order to assess the oxygen demand of the water body,five-day biochemical  oxygen demand (BOD5) test is typically used. BOD 5 represents the sum of the biological  (mostly microbial activity) and chemical (i-e.,oxygen lost in chemical transformation processes) oxygen depleting factors which occur over a five-day period under specific  conditions (20°), and is useful to identity problem areas. High levels of BOD will  rapidly deplete dissolved oxygen stressing aquatic organisms, possibly resulting in  suffocation and death. Low flow conditions in the summer are particularly vulnerable to  excess BOD loading.

Oxygen levels can be measured in the field with a DO probe or through the  Winkler titration method. Samples collected for Winkler tests must be filled completely  with no air left in the sample bottle and should be fixed immediately with acid if the  titration will be done later in the lab. To monitor for low oxygen levels, it is best to  sample early in the morning before the daily photosynthetic period begins.

BOD tests require samples be split into two aliquots at the laboratory and  saturated with DO. One is tested immediately for DO and the other is incubated in the  dark for 5 days at 20° and then the DO is measured. The difference represents the BOD  for the test. If BOD is so high that the oxygen would be completely consumed, dilution  may be necessary. BOD samples should be collected in dark bottles to fibit dl  photosynthesis.

PH  pH is a measure of the degree of acidity of a solution and is measured on a scale  of 1 (most acid) to 14 (most alkaline), with pure water having a neutral pH of 7-0. The  pH scale measures the inverse of the logarithmic concentrations of hydrogen (H^) ions in  water, some of which dissociates to hydrogen (FT^)and hydroxide (OH')ions. Acid  solutions have a higher proportion of hydrogen (H4) ions.Since the scale is logarithmic, a  solution with pH of6.0 is ten times as acidic as a solution with a T)H of7.0.  The pH affects many chemical and biological processes in the water and can  strongly influence which aquatic organisms are lively to flourish in a stream. Most  aquatic organisms prefer a near neutral range of 6.5 to 8.0and can become severely  stressed outside of this range. Additionally, low pH levels result in many toxic  substances(especially heavy metals) becoming more soluble and thus more bio available  (and toxic) to aquatic organisms. Changes in pH can be caused by photosynthesis by  plants;atmospheric deposition (acid rain); dissolution of certain types of rock (especially  sulfide minerals such as pyrite); as well as certain pollutants or waste water discharges.  As discussed earlier, alkalinity acts as a buffer and makes a stream more resistant to  changes in pH.

pH is normally measured in the field either with a pH meter o rwith color  comparator kits that add a reagent to the water that colors a sample. The color is then  compared to a standard color chart that matches colors to pH.An approximate pH can be  determined with simple litmus paper.

Phosphorous    Both phosphorous (P) and nitrogen are essential nutrients for plants and animals.  Both must be present and in certain ratios for plants to thrive. Plants require nitrogen and  phosphorous in an approximate 10to 1ratio and either nitrogen or phosphorous can be a  limiting nutrient depending on relative availability. In freshwater,phosphorous is  typically the limiting nutrient and is also typically somewhat easier to control than  nitrogen. As a result, most nutrient-limiting programs focus on controlling phosphorous.

Phosphorous in streams comes from both natural sources such as rocks, minerals,  and animal wastes, as well as anthropogenic (generated by man) sources such as  waste water treatment plants or fertilized fields and lawns. Phosphorous in aquatic  systems occurs as organic phosphorous (bound inorganic matter) or inorganic  phosphates, comprised of ortho phosphates (~04'~ or polyphosphates. While .   o rHPCV')  animals can use either organic or inorganic P, plants require inorganic P,with dissolved  ortho phosphate being the most bio available form.

Like nitrogen, phosphorous in the environment continually cycles between these  various forms. Aquatic plants take up dissolved, inorganic phosphorous and convert it to  organic phosphorous in plant tissue. As plants and animals excrete wastes or die, this  organic detritus settles to the bottom and is broken down to inorganic form by bacteria.  The inorganic P can be in either dissolved or particulate (bound to sediment particles)  form. The particulate phosphorous in the sediments or in runoff is not considered  bio available but can become bio available if it is stirred up or if ambient conditions,  especially pH or redox conditions change. Under low oxygen conditions, such as occurs  in the bottom of stratified lakes in the summer, phosphates can be reduced and become  much more soluble. This can often trigger an algae bloom if excess nitrates are available.

Because of the complexity of the various forms of phosphorous, various types of  phosphorous measurements are done in the laboratory. When collecting samples for  phosphorous tests, all samples containers must be thoroughly rinsed after cleaning with  non-phosphate detergents. Samples should be fixed with acid and refrigerated. If  samples are to be analyzed for ortho phosphate,they should be analyzed within 48hours  of collection.

Total Solids    Total solids are dissolved solids (TDS) plus suspended and settleable solids (TSS)  in water. In water quality terms, dissolved solids refer to ions and other particles that will  pass through a 2-micron filter and suspended solids are those that won't pass through the  filter. Settleable solids will settle within one hour in an hnhoff cone. Essentially all  contaminants in the water other than dissolved gases contribute to the solids load. The  concentration of dissolved solids changes the ionic strength of the water and affects the  water balance of aquatic organisms. Organisms in pure, distilled water will swell as  osmosis moves water into cells whereas organisms placed in high TDS water will tend to  shrink. This can affect the organisms' ability to maintain homeostasis and density and  make it difficult to maintain it's proper location in the water column. High TDS can lead  to scale forming in pipes. Sources of solids include industrial and municipal discharges,  stom water-off, and eroding stream banks. Use of road salt in the winter can  significantly increase TDS. The general PA state criterion for TDS is 500 mg/1 as a  monthly average value with a maximum of 750 mg/1.

High TSS can result in a high load of adsorbed toxics or bacteria and increase    turbidity as discussed in the next section. High TSS can increase water temperature and    inhibit productivity by blocking light. In addition to the effects on drinking water    suppliers discussed earlier, high TSS can reduce the efficiency of waste water treatment    plants and industrial processes that use raw water,    Regular monitoring of total solids can help detect trends that might indicate  increased erosion or pollutant loading in developing watersheds. TSS in particular is also    dependent on stream flow and velocity and those parameters should also be measured  when taking TSS samples. Total solids are measured in the laboratory by weighing a  beaker with an accurate scale, filling it with water and weighing it again and then  completely evaporating the water, drying the residue, and reweighing to calculating the  weight of the residue. TDS and TSS are calculated similarly by first passing the sample  through a 2-micron filter. Samples collected for solids measurements should be processed  within 7daysofcollection.

Turbidity    Turbidity is a measure of water clarity that describes the degree to which light  passing through water is scattered. Turbidity is caused by fine suspended soil particles  (-004mto 1.0m),algae, plankton, and other substances, and affects the clarity of the  water. Sources of turbidity include soil erosion, waste discharges, urban runoff, eroding  stream banks, bottom feeding fish such as carp, and excess algal growth.

High turbidity can lead to increased water temperatures as suspended particles  absorb heat. This inturn can reduce dissolved oxygen concentrations. Additionally, light  cannot penetrate as far in turbid waters and photosynthesis is inhibited, further reducing  available oxygen. Suspended matter can clog fish gills, lower growth rates, and affect  reproduction. When velocities slow and these fine particles settle out they can smother  fish eggs as well as benthic macroinvertebrates.

Turbidity is a useful indicator of the effects of runoff and can be used as a    "trigger" to determine when to collect samples for parameters such as fecal coliform and    total suspended solids (TSS) that are correlated with high runoff events. Turbidity often    increases sharply during rainfall in developed-watersheds like the Wissahickon that have    high percentages of impervious surfaces. This can be a significant issue for drinking    water suppliers such as the Philadelphia Water Company because it requires them to use    more chemicals for flocculati onto remove suspended solids and can inhibit the    effectiveness of bacterial disinfection by chlorination.

Turbidity is generally measured with a turbidity meter (also called a turbidi meter  or nephelo meter) that uses a calibrated light source to measure turbidity in nephelometric  turbidity units (NTU). An alternative way of estimating transparency is with a Secchi  disk or transparency tube although that is not a true turbidity measurement. Samples  collected for measurement by a laboratory should be refrigerated and processed within 24  hours of collection.

Water Temperature    Temperature is an important basic water quality parameter that strongly influences the rates of iological and chemical processes. The effects on dissolved    oxygen have already been discussed. Fish and other aquatic organisms often require certain temperature ranges to survive or to reproduce. Development of a watershed  generally results in an overall increase of average water temperatures as vegetated    canopies that provide shade are removed, impoundments created, increased surface moff replaces cooler groundwater.flow, and waste water or cooling water flow becomes    a larger component of base flow.

Temperature readings are taken in the field with a calibrated thermometer. The  readings should be taken at mid-depth, away from feebank. As a Pennsylvania TSF  stream, the Wissahickon must meet temperature criterion, Temp3 (PA Code Section 25,  Chapter 93). This means that discharges may not raise temperatures by more than 2¡ in  a one-hour period and no rise is permitted when ambient temperature is 87¡ or above.  The maximum temperature in the stream should not exceed:   

Jan 1-31
Feb 1-29
Mar 1-31
Apr 1-15
Apr 16-30
May 1-15
May 16-31
Jun 1-15
Jul 1-31
Aug 1-15
Aug 16-30
Sep 1-15
Sep 16-30
Oct 1-15
Oct 16-31
Nov 1-15
Nov 16-30
Dec 1-31




To protect and improve the watershed of Great Pond and Long Pond through preservation, education, and action.

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Belgrade Lakes Association

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