pH
The balance of positive hydrogen ions (H
+
) and negative hydroxide ions (OH
-
) in water determines how acidic or basic the water is. Notice the “+” and “–” in the chemical symbols. They show that these chemical forms “ions” - they have a positive or negative electrical charge. This means that the molecule in question is either missing an electron or has an extra electron. Since electrons have a negative charge, and an additional one in the OH molecule it makes OH
-
, and a missing one in the H molecule gives it a "missing-minus" charge — in other words, positive — and makes it H+. When analysts measure pH, they determine the balance between these ions.
The pH scale ranges from 0 (high concentration of positive ions of hydrogen, strongly acidic) to 14
(high concentration of negative hydroxide ions, strongly Basic). In pure water, the concentration of the positive hydrogen ions in equilibrium with the concentration of negative hydroxide ions and pH measures exactly 7.
In a lake or pond, water pH depends on age and chemical substances released from the community and industry. Most of the lakes are basic when they are first formed and become more acidic with time due to the accumulation of organic matter. As the disintegration of organic matter, carbon dioxide and combined with water to form a weak acid called “carbonic” acid-the same material, which is in carbonated soft drinks. A large quantity of carbonic acid lower water’s pH. Most fish can tolerate pH values of about 5.0 to 9.0, but serious anglers look for waters between pH 6.5 and 8.2.
Effects of pH on fish and aquatic life
Min
3.8 pH value
Max
10.0
4.0
4.1
4.3
4.5
10.1
9.5
--
9.0
Effects observed under research
Fish eggs could be hatched, but deformed young were often produced.
Limits for the most resistant fish species.
Range tolerated by trout.
Carp died in five days.
Trout eggs and larvae develop normally.

4.6
5.0
5.0
--
5.4
6.0
1.0
3.3
7.5
9.5
--
9.0
8.7
11.4
7.2
--
4.7
8.4
Limits for perch.
Limits for stickleback fish.
Tolerable range for most fish.
Upper limit for good fishing waters.
Fish avoided waters beyond these limits.
Optimum (best) range for fish eggs.
Mosquito larvae were destroyed at this pH value.
Mosquito larva lived within this range.
Best range for the growth of algae.
Production processes that use water can influence the level of acidity and pH is regulated in many cases by adding chemicals or buffers. The following table shows the optimal pH for several different manufacturing processes.
Optimal pH for industrial water supplies
Process
Food canning and freezing
Washing clothes
Rayon manufacturing
Steel making
Tanning leather
Minimum
7.5
--
--
--
-- pH Range
--
6.0-6.8
7.8-8.3
6.8-7.0
6.0-8.0

Turbidity
Turbidity is the optical property of water that causes light to be scattered and absorbed rather than transmitted in straight lines through the sample. The ability of light to pass through water depends on how much suspended material is present. Turbidity may be caused when light is blocked by a large amount of silt, micro-organisms, plant fibers, sawdust, ash wood, chemicals and coal dust. Any substance that makes water cloudy will cause turbidity. The most frequent causes of turbidity in lake and river are plankton and erosion of soil from logging, mining and dredging.
Turbidity level of water for industrial use
Industrial Use
Beverages
Food products
Water used in boilers
Making high grade paper
Making rayon
Making cotton
Baking
Water used for cooling
Ice making
Tanning leather
Maximum Turbidity Units
1-2
10
1-20 (varies with type of boiler)
5-25
1
25
10
50
0.5 (same as drinking water)
20
Interference with sunlight penetration. Water plants need light for photosynthesis. If suspended particles block out light, photosynthesis—and the production of oxygen for fish and aquatic life—will be reduced. If light levels get too low, photosynthesis may stop altogether and algae will die. It’s important to realize conditions that reduce photosynthesis in plant result in lower oxygen concentrations and large carbon dioxide concentrations. Respiration is the opposite of photosynthesis.
Turbidity affects fish and aquatic life by intervention by the penetration of sunlight. Water plants need light for photosynthesis. If the suspended particles blocking light, photosynthesis and the production of oxygen for fish and aquatic life will be reduced. If the light levels become too low, photosynthesis may

stop altogether and algae will die. . It’s important to realize conditions that reduce photosynthesis in plant result in lower oxygen concentrations and large carbon dioxide concentrations. Respiration is the opposite of photosynthesis.
A large number of suspended matters may clog the gills of fish and shellfish and kill them directly.
Particulate matter can provide a place for harmful microorganisms to lodge. Some of the suspended particles can serve as a breeding ground for bacteria. Fish cannot see well in turbid water and therefore may have difficulty finding food. On the other hand, turbid water may make it easier for fish to hide from predators. The following table shows the number of plankton with acres that you can expect in various bodies of water turbidity.
Plankton density as a function of water turbidity
Clear lake less than 25
Intermediate lake
25-100
Muddy lake over 100
Factor measured
Average turbidity units:
Amount of fish in pounds per acre:
Comparative amount of plankton caught in nets
162
12.8
94
1.6
29
1

Dissolved oxygen
Dissolved oxygen, oxygen, dissolved in the water. It falls there by diffusion from the ambient air, the aeration of water, which fell to the waterfalls and the thresholds, and also as the by-product of photosynthesis. The more simplified formula is given below:
Photosynthesis (with the presence of light and chlorophyll):
Carbon dioxide (CO
2
) + Water (H
2
O) -> Oxygen (O
2
) + Carbon-rich foods (C
6
H
12
O
6
)
Fish and aquatic animals are unable to separate oxygen from water and other oxygen-containing compounds. Only green plants and some bacteria can do it through photosynthesis and similar processes. Almost all oxygen that we breathe is made by green plants. A total of three quarters of the
Earth's oxygen is made by phytoplankton in the oceans. If the water is too warm, there might not be enough oxygen in it. When too much bacteria and water animals in the area, they are overpopulating, using DO in great amounts. Oxygen levels also can be reduced through over fertilization of water plants by run-off from farm fields containing phosphates and nitrates (the ingredients in fertilizers).
Under these conditions, the numbers and size of water plants increase a great deal. Then, if the weather becomes cloudy for several days, respiring plants will use much of the available DO. When these plants die, they become food for bacteria, which in turn multiply and use large amounts of oxygen.
Numerous scientific studies suggest that 4-5 parts per million (ppm) of DO is the minimum amount that will support a large, diverse fish population. The DO level in good fishing waters generally averages about 9.0 parts per million (ppm).
When DO levels drop below about 3.0 parts per million, even the rough fish die. The table in this section shows some representative comparisons.
Effect of dissolved oxygen level on fish
Fish
Species
Lowest DO level at which fish survive for:
24 hours (summer) 48 hours (winter)

Yellow Perch
Black Bullhead
Black Bass
Northern Pike
4.2 mg/L
3.3
5.5
6.0
4.7
1.1
4.7
3.1
How Dissolved Oxygen Affects Water Supplies
A high DO level in a community water supply is good because it makes drinking water taste better.
However, high DO levels speed up corrosion in water pipes. For this reason, industries use water with the least possible amount of dissolved oxygen. Water used in very low pressure boilers have no more than 2.0 ppm of DO, but most boiler plant operators try to keep oxygen levels to 0.007 ppm or less.
Eutrophication
Eutrophication is when the environment becomes enriched with nutrients. This can be a problem in marine habitats such as lakes as it can cause algal blooms.

Fertilizers are often used in farming, sometimes these fertilizers run-off into nearby water causing an increase in nutrient levels.

This causes phytoplankton to grow and reproduce more rapidly, resulting in algal blooms.

This bloom of algae disrupts normal ecosystem functioning and causes many problems.

The algae may use up all the oxygen in the water, leaving none for other marine life. This results in the death of many aquatic organisms such as fish, which need the oxygen in the water to live.

The bloom of algae may also block sunlight from photosynthetic marine plants under the water surface.

Some algae even produce toxins that are harmful to higher forms of life. This can cause problems along the food chain and affect any animal that feeds on them.

Conductivity
The specific conductance test measures the ability of water to pass an electrical current. Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, sulfate, sodium, calcium and others.
Conductivity in streams and rivers is affected by the geology of the area through which the water flows.
Streams that run through granite bedrock will have lower conductivity, and those that flow through limestone and clay soils will have higher conductivity values. High conductance readings can also come from industrial pollution or urban runoff - water running off of streets buildings, and parking lots.
Extended dry periods and low flow conditions also contribute to higher specific conductance readings.
Because an organic compound such as oil does not conduct electrical current very well, an oil spill tends to lower the conductivity of the water. Temperature also affects conductivity; warm water has a higher conductivity. Specific conductance is measured in microsiemens per centimeter (µs / cm).