Water Quality Indicators Notes

What is an Indicator?
 Water is seen as “good quality” or “bad quality” based
off of several criteria
 These criteria indicate the health of the water
 Includes turbidity, pH, dissolved oxygen, temperature,
nitrates, and bio-indicators
Definition: Turbidity
 Turbidity: measure of the degree to which water looses
its transparency due to the presence of suspended
This is a river with high turbidity 
Levels: Turbidity
 Ideal level: 1 NTU (Nephelometric unit)
 High level: 5 NTU
Causes: Turbidity
 Causes of increased turbidity:
Increased levels of phytoplankton sediment from
erosion, re-suspended sediments from the bottom
(stirred by bottom dwellers), waste discharge, algae
growth, and urban runoff
Results: Turbidity
 Results of high turbidity:
High turbidity increases the
absorption of sunlight thus
making the water warmer.
Warmer water has lower levels of
dissolved oxygen causing fish
and larvae to die
Definition: pH
 pH: the acidity of the water (presence of hydrogen ion)
 07 is acidic
 7 is neutral
 7 14 is basic
Levels: pH
 Surface Freshwater: 6.0  9.0
 Swamps: as low as 4.3
 Salt Water: 8.1 but as low as 7.7
Causes: pH
 Causes of changes of pH:
 Natural conditions (especially
in swamps), dumping of waste
(batteries) and farm runoff
Results: pH
 Results of changes of pH:
 A change in pH by 2 units results in a water system
having 100 times a difference in acidity
 Most aquatic life cannot withstand water outside the
optimum pH thus resulting in death
Definition: Dissolved Oxygen
 Dissolved Oxygen: the oxygen dissolved in the water
Levels: Dissolved Oxygen
 Average level: 9.0 ppm (parts per million)
 Must be 4-5 ppm to support diverse population of fish
Causes: Dissolved Oxygen
 Causes of changes in dissolved oxygen: turbulent
actions (waves, rapids), water depth, and plant growth
Results: Dissolved Oxygen
 Results of changes in dissolved oxygen:
 When DO drops too low, fish die
 When DO is high, the water actually tastes better but
can corrode water pipes
Definition: Temperature
 Temperature: the measure of average kinetic energy
Levels: Temperature
 Low: cannot be tolerated below 32 degrees F
 High: only rough fish can tolerate temperatures above
97 degrees F
Causes: Temperature
 Causes of change in temperature: source of water, time
of year, suspended sediment, depth of water, and
shade from shoreline vegetation
Results: Temperature
 Results of changes in temperature: changes in
temperature can make aquatic life susceptible to
disease and at extreme levels can result in death
Definition: Nitrates
 Nitrates: compound that contains the nitrogen based
polyatomic ion NO3 (Ex: Sodium Nitrate)
Levels: Nitrates
 Drinking Water Max: 10 mg/L
 Fish: Below 90 mg/L seems to have no effect on warm
water fish
Causes: Nitrates
 Causes of nitrates:
 Fertilizer runoff (both farm and
home), manure pits, leaks in
septic systems, animal waste, and
rain trapping car exhaust
Results: Nitrates
 Results of presence of nitrates:
 Nitrates can increase the plant production and fish
population resulting in overcrowding
 If algae increases due to nitrates, the pH levels
decrease killing fish
 Nitrates are converted to nitrites in humans (can kill
Definition: Bio-indicators
 Bio-indicators: macroinvertibrates found living in
water (they tend to remain in one place) that are
sensitive to pollution
Levels: Bio-indicators
 High level of variety: healthy water source
 Small level of variety: poor water source (indicator of
high levels of pollution)
Causes: Bio-indicators
 Causes of changes in bio-
Pollution that results in
changes in pH,
temperature, dissolved
oxygen, or nitrate levels
Results: Bio-indicators
 Results of few varieties of bio-indicators present: the
lack of a large number of different varieties of bioindicators is indicative of pollution
 Title Page – Use title given on Table of Contents. Add Name, Date, Block Color
in upper right hand corner. Page number goes on the bottom outermost corner
of the foldable. Title: Water Quality Indicators Foldable Page # 48
 Each Tab Should have the following:
 Title of Indicator:
1. What is an indicator?
2. Turbidity
3. pH
4. Dissolved Oxygen
5. Temperature
6. Nitrates
7. Bio-Indicators
 Definition & Levels
 Causes
 Results
All WORDS should be in color! NO PENCIL. You may use pen, markers, or colored
All PICTURES should be fully colored!
All BACKGROUNDS should be fully colored!