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5.1  pH

Water contains both hydrogen ions (H+) and hydroxide ions (OH-). pH measures the concentration of hydrogen ions in a substance. To mathematically calculate the pH of a substance, use the following equation:            pH = -log10 [H+] 

The concentration of hydrogen ions shows the acidity of the substance. A low pH is highly acidic, and a high pH is highly alkaline. Pure water, which is neutral, has a pH of 7. Acidic water has a pH of 0-6, and basic water has a pH of 8-14. Table 5.1.1  shows different substances and their normal pH.           

Type of Substance

pH Range

Battery Acid


Lemon Juice




Orange Juice




Normal Rainwater


Distilled Water




Baking Soda


Milk of Magnesia






Household Lye


Table 5.1.1    A variety of substances and their pH range. 

It is generally accepted by the scientific community that adding acid to water will always alter the pH. Several sources of decreasing pH include:

 Acid Rain

The United States is notorious for having dirty air and lots and lots of evil pollutants. Emissions from cars, factories, and other sources of air pollution contain nitrogen oxides (NOx-s) and sulfur dioxide (SO2-). The NOxs and SO2- react in the atmosphere to form nitric acid and sulfuric acid. After this wonderfully complex chemical process, the acid lowers the pH of rivers, streams, brooks, lakes, oceans, runlets, streamlet, springs, cricks, and creeks. 

Acid rain is damaging to the environment in many respects. For example, thousands of lakes in eastern Canada and the northeastern region of the United States are becoming dangerously acidic. The average pH of these waterways is around 4.0, which is a hundred times more acidic than safe levels. The regions that have the worst cases of acid rain, however, are downwind of urban and industrial areas, and contain no minerals to neutralize the acidic effects of acid rain.   

Acid Mine Drainage

Coal mining and the use of coal put water quality in danger. Bituminous coal contains 32 percent sulfur, and is the most commonly mined coal in the world. During the mining process, the sulfur in coal is exposed to the oxygen in air. Reactions occur, with the final result being the sulfide compounds converted to sufuric acid and ferric sulfate. Rainfall and groundwater seepage allow the exposed sulfur and iron to wash into surface water. Surface water that has mine drainage in it is normally acidic and lowers the pH. In the United States, 10,000 stream miles have been contaminated by mine drainage. 

Organisms are adversely affected by decreasing pH in many streams and creeks. Most organisms have adapted to life in water of a specific pH and may die even with a slight change in pH. 


pH Range





Rooted Plants


Carp, Catfish


Bass, Crappie


Snails, Clams, Mussels


Mayflies, Caddisflies, Stoneflies




Trout and other Fish


Table 5.1.2    Some organisms and the pH range in which they live in. 

Acidic water in a stream ecosystem can cause several problems. Young fish are extremely sensitive to low pH values, such as those below 5, as well as aquatic insects. Excessive acidity in streams can also lead to the release of heavy metals such as copper and aluminum into the stream. This can lead to deformities in young fish and the accumulation of heavy metals in the gills of fish. In most cases the heavy metals would be washed away with sediment in the stream, but with higher concentration of hydrogen ions the heavy metals remain. Acidic levels of pH also can lead to retardation in aquatic wildlife. The stages of embryonic development for both species of salamanders and frogs result in a 100% mortality rate in pH levels below 5.0.

5.2  Turbidity

The difference between murky water and clear water is a lot more than the overall color: the real difference lies in the turbidity. Turbidity measures the clarity of water in a relatively simple method—the higher the turbidity, the murkier the water. Turbidity essentially measures the number of suspended solids in a water substance, as suspended solids reduce the transmission of light. Examples of suspended solids include silt, plankton, and clay in addition to industrial wastes and raw sewage.  

Turbidity is mainly caused by soil erosion and runoff, because when sediment is released into streams through erosion and runoff, many of the soil particles becomes suspended in the water. Suspended solids also occur when wastes are discharged from factories and urban runoff. Algae growth is also a source of suspended particles, as the result of eutrophication. Turbid water may also contain micro-organisms such as bacteria and viruses. Finally, asbestos has been found in several rivers in the Deep South with high turbidity.  

Many turbid rivers contain both point and non-point sources. Point sources include sewage treatment plants that discharge organic waste. Non-point sources include natural in-stream detritus, particulate matter, phytoplankton production, and nutrients contributed by industrial waste. 

Sediment Class




Very coarse

1.5 mm



0.375 mm


Very fine

0.094 mm


Very coarse

0.047 mm



0.0117 mm


Very fine

0.0049 mm



< 0.00195 mm

Suspended solids in water systems are measured in Nephelometric Turbidity Units (NTU) or in Jackson Turbidity Units (JTU). For the purposes of our project, however, the units used are NTUs. Suspended solids in lake water systems normally contain small sediment fractions, such as medium (0.0117 mm) and very fine silt (0.0049 mm) and clay (0.00195 mm). Suspended solids in running water systems, like Bear Creek, normally contain larger particles such as very coarse silt (0.047 mm) and very fine sand (0.094 mm). Acceptable NTU ranges according to government standards are shown on the next page. 

Designated Use




Aquatic Life

< 50 NTU (instantaneously)


< 25 NTU (10 day average)

Human Consumption

1-5 NTU

Table 5.2.1    Acceptable ranges (in NTU) for different uses of water 

Both organic and inorganic materials are found in turbid water. Possible health hazards include microorganisms found in organic material. If turbidity is largely due to organic particles, the dissolved oxygen content might decrease. Excess nutrients available will encourage breakdown of organic material, a process that requires dissolved oxygen. In addition, excess nutrients can stimulate algae growth, which eat up dissolved oxygen as well. It is important to realize that while turbid water is not necessarily harmful, it can indicate much more serious problems. Water high in turbidity can block disinfectants from destroying water contaminants such as bacteria and viruses. Turbidity particles also absorb dissolved water contaminants and carry them throughout the water system. Asbestos, lead, and microorganisms also can be suspended solids themselves, and the presence (in high amounts) of any of them is a health hazard by itself. Protozoan cysts such as Giardia and C-tosioridum are also found in waters with high turbidity. In order to remove these health effects, turbidity problems can be solved with point-of-use water filtration systems specially designed to remove small particles. 

5.3  TDS & Conductivity

Suspended solids are measured by turbidity, yet turbidity does not factor in dissolved solids that are found in a water sample that passes through a filter. Dissolved or inorganic materials include calcium, nitrogen, phosphorous, iron, sulfur, bicarbonate, and several other ions naturally found in a water ecosystem.  

Many sources will affect the amount of TDS in a water system. Runoff from urban and industrial areas is the most common, because normally runoff will contain salt from streets in winter, fertilizers, and other salt-like material found in residential, commercial, and industrial areas. Sewage treatment plants, both primary and secondary, will often add phosphorous and nitrogen to water systems as well. 

Water quality and aquatic life are adversely impacted by the levels of TDS and/or the water’s conductivity. High concentrations of TDS will lower water quality, yet low concentrations will limit the growth of aquatic life. High concentration of suspended solids will also reduce water clarity, contribute to a decrease in photosynthesis, add even more problems by binding with heavy metals, and lead to an increase of water temperature.  

Conductivity is the measurement of a solution's ability to conduct an electrical current. Chemically speaking, pure water is a horrid electrical conductor. Therefore, a conductive water solution will contain dissolved substances or salts. Because of this, conductivity is an excellent indicator of soil salinity and fertilizer concentrations.  

When using conductivity to help determine water quality for a water body, the rationale is simple: the higher the conductivity, the more salts are dissolved in the water. Environmental conditions such as drought, changing seasons, and heavy rainfall, all have an impact on the concentration of dissolved salts in water. These dissolved salts, such as calcium, sodium, magnesium, and so on, can directly affect water ecosystems. 

Specifically, conductivity is dependent upon the concentration or number of ions, the mobility of those ions, the oxidation state, and the temperature of the water. For our test, conductivity is expressed in microohms, the standard unit of measure for conductivity. Since conductivity is related to ionic strength, there is no way to determine from a simple conductivity test which ions are present in water.  

Conductivity determines mineralization, and is closely linked with Total Dissolved Solids (TDS). The number of available ions in the water often affects certain physiological effects on plants and animals. Conductivity also notes variation or changes in natural water and wastewaters, in addition to determining amounts of chemical reagents or treatment chemicals to be added to a water sample.  

Elevated dissolved solids can cause "mineral tastes" in drinking water. Corrosion or encrustation of metallic surfaces by waters high in dissolved solids causes problems with industrial equipment and boilers as well as domestic plumbing, hot water heaters, toilet flushing mechanisms, faucets, and washing machines and dishwashers. Agriculturally, excessive dissolved solids can be a problem in irrigation water and water used for livestock. Indirectly, excessive dissolved solids will basically deplete the growth of vegetation, eliminating food plants and habitat for many aquatic organisms.

There are no current standard criteria for acceptable levels of conductivity. Most water-quality experts, however, recommend a cutoff of around 150 microohms in water for conductivity.

5.4  Temperature

The water temperature of a water system is vital to the water quality and health of and aquatic organisms. Physical, chemical, and biological characteristics are affected by changes in temperature. Temperature has an effect, whether it be direct or indirect, on dissolved oxygen, photosynthesis, metabolism, and sensitivity to toxins. But its primary and most immediate effect is on dissolved oxygen.  

As temperature increases, the solubility of oxygen decreases.  Eventually DO will reach levels that cannot support life if the temperature is high enough.  This is  called “thermal pollution” and can kill fish.  Industry is largely responsible for this type of pollution. 

Temperature is measured with a thermometer. 

Temperature Range

Life that Lives

> 20 degrees C

Most plant life, many fish, bass, crappie, catfish, bluegill, and carp

15 < 20 degrees C

Some plant life, some fish, salmon, trout, stonefly nymphs

11 < 15 degrees C

Mayfly nymphs, caddisfly larvae, water beetles, and water striders

11 degrees C <

Trout, caddisfly larvae, stonefly nymphs, and mayfly nymphs

Table 5.4.1  The Temperature range of tolerance for some aquatic organisms

5.5  Flow

These things are important insofar as they tend to be indicative of the overall health of the watershed.  For constant rainfall, the higher the flow, the more water is running off and the less infiltration and consequent replenishment of groundwater is occurring.  High runoff is not a good thing.  In addition to slowing the recharge rate of the aquifer, it also means that less water is being stored in other important places, such as wetlands, for slow, gradual release over the dry summer months.  Water that runs off tends to carry topsoil with it.  This process is bad for 2 reasons: not only does it make the land not so fertile anymore, but that eroded sediment can make it impossible for salmon to reproduce successfully by clogging their gravel spawning beds.   

Runoff and thus large flow and depth are dramatically increased by developments.  Areas that are covered in concrete, asphault, and steel do not absorb water particularly well.  This water has no place to go but into storm drains and eventually creeks, carrying with it all sorts of nasty stuff.  This problem is intensified when wetlands are destroyed. 

Flow is measured with a little spinny-wheel thing that goes in the creek.  Depth is measured with a big wood stick with measurements on it.  The procedure for measuring flow is as follows.  First, a channel cross-section must be mapped out and an area calculated.  After this has been done, the water-velocity-measuring-thing is plunged into the water at regular intervals and depths.  If the creek is deep, several depths should be taken.  If it is shallow, the tool should be inserted to 60% of the depth of the water, the place where the faster surface velocity is averaged with the slower bottom velocity.

The flow is then calculated by plugging the average velocity into a handy little equation that came with the flowmeter. 

Flow was measured in three spots. These were the same spots where we measured depth. A schematic below shows this: 

We submerged the flow meter in three depth levels. We took the averages (in our heads) and came to a number for flow for that specific spot. The flow measurements 

Depth is calculated by measuring how deep the water is with a yardstick.

5.6  Water Volume

The measure of volume of water was approximated with geometric shapes since finding a complex mathematical function of the bottom of the stream would make the calculus very messy. Below is a schematic of what we did:


We basically took three depth measurements, one on each side and one in the middle. We took the averages of the total 20 days of measurement to get an average measurement, which would be used, in determining the average volume. 

They were set apart equally which means the creek was divided into fourths. These heights of the rectangles were found through the side water depth measurements and gave us one side to two of the triangles. The bottom two triangles were kind of tricky. One of the side depth values was subtracted from the middle depth value to get side of the bottom triangles. To clarify this procedure there are pictures below:

Let us assign DEPTH as variable “a”, WATER DEPTH as “b” and “LENGTH” as “c”. This means the volume of the rectangular solid is equal to the product of a,b and c.

From the measurements from in the field we can find the area of the base which is (1/2)(LENGTH)(WATER DEPTH) and times it by the (DEPTH) to find the volume of the triangular solid.


In the picture above you can see that the side water depth value can be subtracted from the middle depth value to get the side of the triangle which is needed to find the volume of the triangular solid.  

Approximation of both rectangles and triangles yield 2 rectangular solids and 4 triangular solids. By adding the volume of the triangular solids and rectangular solids you get an approximation of how many cubic feet of water is flowing through the creek. The depth was set as a constant factor of 1 foot. We set markers on each side of the creek. If there were ropes from marker to a marker on the side the two ropes would be parallel.  




Average Depths of Water


1 ft.

10.71 ft.

3.46 ft. / 5.54 ft. / 4.45 ft.

Redmond Town Center

1 ft.

11.32 ft

3.48 ft. / 5.21 ft. / 4.09 ft.

Cottage Lake

1 ft.

5.21 ft.

0.55 ft. / 0.83 ft. / 0.37 ft.

  Volume Calculations 

Average Volume at Bridge = Rectangle Volume + Triangle Volume =

[(1 ft)(10.71 ft)(1/4)(3.46 ft) + (1 ft)(10.71 ft)(1/4)(4.45 ft)] + [(1/2)(10.71 ft)(1/4)(5.54 ft – 3.46 ft)(1 ft) + (1/2)(10.71 ft)(1/4)(5.54 ft – 4.45 ft)(1 ft) + (1/2)(10.71 ft)(1/4)(3.46 ft)(1 ft) + (1/2)(10.71 ft)(1/4)(4.45 ft)(1 ft)] = 35.530425 cubic feet

 Average Volume at Redmond Town Center = Rectangle Volume + Triangle Volume =

[(1 ft)(11.32 ft)(1/4)(3.48 ft) + (1 ft)(11.32 ft)(1/4)(4.09 ft)] + [(1/2)(11.32 ft)(1/4)(5.21 ft – 3.48 ft)(1 ft) + (1/2)(11.32 ft)(1/4)(5.21 ft – 4.09 ft)(1ft) + (1/2)(11.32 ft)(1/4)(3.48 ft)(1 ft) + (1/2)(11.32 ft)(1/4)(4.09 ft)(1 ft)] = 36.1674 cubic feet

 Average Volume at Cottage Lake = Rectangle Volume + Triangle Volume =

[(1 ft)(5.21 ft)(1/4)(0.55 ft) + (1 ft)(5.21 ft)(1/4)(0.37 ft)] + [(1/2)(5.21 ft)(1/4)(0.83 ft – 0.55 ft)(1 ft) + (1/2)(5.21 ft)(1/4)(0.83 ft – 0.37 ft)(1 ft) + (1/2)(5.21 ft)(1/4)(0.55 ft)(1 ft) + (1/2)(5.21 ft)(1/4)(0.37 ft)(1 ft)] = 2.279375 cubic feet

5.7  Dissolved Oxygen

Simply put, dissolved oxygen is the volume of oxygen gas that is contained in water. The level of dissolved oxygen is extremely important to organisms, as organisms use oxygen to produce ATP. Oxygen enters water through two methods: photosynthesis and the air-water interface. Three factors determine the capacity of the water: temperature, salinity, and pressure. Gas solubility increases when temperature and salinity decrease, and decreases when pressure decreases according to the wonderful AP Chemistry textbook. In other words, colder water holds more oxygen, freshwater holds more oxygen than saltwater, and since pressure change with altitude, solubility decreases when altitude increases.  

Dissolved oxygen, otherwise known as DO, is essential for the health of lakes, streams, rivers, and creeks. Most, in fact nearly all, aquatic plants and animals require oxygen to survive. In flowing water, turbulence causes water with less oxygen to switch with water with more oxygen at the surface level. A high temperature leads to a loss of oxygen. As the temperature increases, the density of the water decreases. This process is known as stratification, a seasonal process. This is why warm water remains at the surface while colder water is found beneath to the surface (normally in the aphotic zone). The top layer of the water, warm and near the surface, is called the epilimnion. The cooler layer at the bottom is referred to as the hypolimnion. The layer in between is called the thermocline.  

Since stratification is a seasonal process, the layers are much more evident in the summertime. As summer starts, most normally healthy water systems have plenty of dissolved oxygen. Yet as eutophication  during the summer occurs, dead organisms clutter the hypolimnion and create an oxygen deficiency. Many streams, creeks, and lakes have continuous eutrophication currently in the United States. For these streams, creeks, and lakes dissolved oxygen levels will continue to decrease until the amount is totally depleted.

Aquatic organisms depend on dissolved oxygen, since all living organisms require oxygen. In fact, without oxygen, you would die. Don't you see the importance of oxygen now? Closer to home, salmon really depend on dissolved oxygen levels. When salmon spawn, there must be a set minimum dissolved oxygen level in order to ensure that there will be enough oxygen in a lake or other water system.  

Designated Use

Lowest Accepable

DO levels (mg/L)

Warm water fish


Cold water fish


Spawning season


Aquatic Life in estuaries


Primary recreational contact


Secondary recreational contact


Table 5.7.1 Acceptable levels of Dissolved Oxygen for various purposes

Water temperature and the discharge of water both affect dissolved oxygen levels. Gases in general, but especially oxygen, dissolve more easily in cooler water than in warmer water. Climate conditions also have a strong impact on dissolved oxygen levels. During dry period, water flow can be substantially reduced, and air and water temperatures are often higher than normal. Both higher temperatures and decreased water flow are known for reducing dissolved oxygen levels.  

Humans also contribute to decreasing levels of dissolved oxygen. The principle factor that causes changes in dissolved oxygen levels is essentially organic matter or waste. Organic wastes consist of anything that came from a plant or animal: food, leaves, crap, etc. Sewage, urban runoff, and agriculture are all causes of organic material that leaks into rivers and waterways. In terms of runoff—both urban and agricultural—fertilizers contribute to organic material. Fertilizers stimulate algae growth and eutrophication, which in turn leads to decreased dissolved oxygen levels.

Excess organic matter, such as dead organisms and waste from those dead, rotting organisms, can result in oxygen depletion in an aquatic life system. If an organism is exposed to dissolved oxygen levels below its minimum, the organism may die directly from a lack of oxygen, however it will also be susceptible to many other diseases. Once the organisms die, only anaerobic organisms can survive in the water. The anaerobic organisms normally have energy bound to molecules like sulfate compounds. During anaerobic respiration, sulfate compounds will be broken down and will put a smell not unlike rotten eggs to the water. This means that all recreational use for the water is done for. Examples of species that can be in danger of dying from low levels of dissolved oxygen are the mayfly nymphs, stonefly nymphs, caddisfly larvae, and beetle larvae, all organisms that were spotted around our sites. 

5.8  Nitrates

Nitrogen is one of the most abundant elements. About 80 percent of the air we breathe is nitrogen. It is found in the cells of all living things and is a major component of proteins. Inorganic nitrogen may exist in the free state as a gas N 2, or as nitrate NO 3-, nitrite NO 2- or ammonia NH3. Organic nitrogen is found in amino acids in proteins, and is continually recycled by plants and animals. The nitrogen cycle is shown below:

Nitrogen is tested for using a chromatographic test.  While fairly crude, this test is accurate enough for our purposes. 

Nitrogen-containing compounds act as nutrients in streams, rivers, and reservoirs. The major routes of entry of nitrogen into bodies of water are municipal and industrial wastewater, septic tanks, feed lot discharges, animal wastes (including birds and fish), runoff from fertilized agricultural field and lawns and discharges from car exhausts. Bacteria in water quickly convert nitrites [NO2-] to nitrates [NO 3 -] and this process uses up oxygen. Excessive concentrations of nitrites can produce a serious condition in fish called "brown blood disease." Nitrites also can react directly with hemoglobin in the blood of humans and other warm-blooded animals to produce methemoglobin. Methemoglobin destroys the ability of red blood cells to transport oxygen. This condition is especially serious in babies under three months of age. It causes a condition known as methemoglobinemia or "blue baby" disease. Water with nitrate levels exceeding 1.0 mg/L should not be used for feeding babies. High nitrates in drinking water can cause digestive disturbances in people. Nitrite/nitrogen levels below 90 mg/L and nitrate levels below 0.5 mg/L seem to have no affect on warm water fish.

The major impact of nitrates/nitrites on fresh water bodies is that of enrichment or fertilization called eutrophication. Nitrates stimulate the growth of algae and other plankton which provide food for higher organisms (invertebrates and fish); however an excess of nitrogen can cause over-production of plankton and as they die and decompose they use up the oxygen which causes other oxygen-dependent organism to die. 

5.9  Phosphates

Phosphorus is one of the key elements necessary for growth of plants and animals. Phosphates PO4--- are formed from this element. Phosphates exist in three forms: orthophosphate, metaphosphate (or polyphosphate) and organically bound phosphate. Each compound contains phosphorous in a different chemical formula. Ortho forms are produced by natural processes and are found in sewage. Poly forms are used for treating boiler waters and in detergents. In water, they change into the ortho form. Organic phosphates are important in nature. Their occurrence may result from the breakdown of organic pesticides which contain phosphates. They may exist in solution, as particles, loose fragments or in the bodies of aquatic organisms.

Phosphates were measured using a crude colormetric analysis.  While not terribly accurate, it was accurate enough, given our very low phosphate levels.

Rainfall can cause varying amounts of phosphates to wash from farm soils into nearby waterways. Phosphate will stimulate the growth of plankton and aquatic plants that provide food for fish. This may cause an increase in the fish population and improve the overall water quality. However, if an excess of phosphate enters the waterway, algae and aquatic plants will grow wildly, choke up the waterway and use up large amounts of oxygen. This condition is known as eutrophication or over-fertilization of receiving waters. This rapid growth of aquatic vegetation eventually dies and as it decays it uses up oxygen. This process in turn causes the death of aquatic life because of the lowering of dissolved oxygen levels.

Phosphates are not toxic to people or animals unless they are present in very high levels. Digestive problems could occur from extremely high levels of phosphate.