Water Quality Parameters
Note: 1 ppm (parts per million) = 1 mg/L,
1 ppb (parts per billion) = 1microg/L
Water Quality
Test
Description
Parameters
Associated Problems
BOD
(Biological
Oxygen
Demand)
DO
(Dissolved
Oxygen)
The amount of oxygen used by
microorganism in the water to
decompose organic matter
1-2 mg/L is very good, 3-5 mg/Lmoderate, 6-9 mg/L
somewhat polluted, > 10 mg/L very polluted , sewage
treatment plants are allowed to discharge 8-150 mg/L
If microorganisms are absent from the stream due to changes in pH etc.
caused by excess sewage, then the organic waste does not decompose and
can cause odor and health problems
The amount of oxygen available to
fish and macroinverterbrates in the
water
Min. required amt (in mg/L) for: warm water fish 5, cold water
fish 6, fish when spawning 7, macroinvertebrates 5,
Recreational use 3
Too little (below 5) and most aquatic animals can't survive.
Biotic Index
The number of different species of
macroinvertebrates in the water
Great diversity -- mayfly, stonefly, caddisfly, salamander,
trout, bass, salmon, pike (Index value >20)
Poor Diversity -- sludge worms, black fly larvae, leeches,
catfish (Index value <10)
Dredging,channeling, and a limited riparian area add sediment to the stream
that can change the makeup of organisms there. Make sure to look in riffle
areas, under large rocks, and in areas with natural debris when looking for
macroinvertebrates.
TDS (Total
Dissolved
Solids)
Conductivity
The measure of the amount of
particulate solids that are in the
water.
Estimate the TDS by multiplying the conductivity reading (in
micromhos/cm) by 0.67. TDS is measured in mg/L.
Safe drinking water levels <500 mg/L
TDS can show areas that have a high mineral base (from rock substrate) or
from dissolved minerals from industry, agriculture, or waste water treatment.
TSS
(Total
Suspended
Solids)
Turbidity
The measure of the amount of
sediment that is in the water. A
Secchi disk is usually used for
lakes and rivers.
Using a Transparency Tube for Streams: (The equivalent
parameters for lakes) Poor visibility <25 cm = 25 NTU,
Visibility for recreational use 50-60 cm = 5 NTU,
Extreme clarity > 60 cm = 0.5 NTU
Sedimentation from agriculture, housing, etc. can clog the gills of fish,
suffocate freshwater clams and other macroinvertebrates.
pH
The measure of acidity (hydronium
ion, H+) in the water
Range for most aquatic life is 6.5 - 8.2
Below 6.5 is too acidic: Above 8.2 is too basic
Increased use of fossil fuels increases the amount of SO2 that mixes with
water to lower the pH. Most organisms can't survive in a pH less than 4.5
Nitrates (NO3)
NO3, NO2, NH3 and organic N are
all found in water. The nitrate test
is a NO3-N complex.
To find the nitrate amount multiply the value by 4.4
Reading of: <1.0 mg/L good, < 5.0 mg/L fair
> 10 mg/L very poor
Excess nitrates and ammonia from fertilizer causes eutrophication of
phytoplankton in streams & lakes
Phosphates
(PO4)
The measure of phosphates in the
water
<0.1 mg/L good, < 0.5 mg/L fair
> 1.0 mg/L very poor
Excess phosphates from fertilizer causes eutrophication of phytoplankton in
streams & lakes. (Phosphate problems were found before nitrate problems)
Hardness
(Ca+2 or Mg+2)
The measure of Calcium and
Magnesium in water
0-60 mg/L indicates soft water, 120-180 indicates hard water,
< 250 mg/L is acceptable for drinking,
> 500 mg/L is hazardous to human health
Although aquatic organsims are not affected by an increase of water
hardness, it does play a role in human lives. Water that is <10 mg/L are
oligotrophic and those containing >25 mg/L are usually eutrophic.
Temperature
Change oC
The measure of temperature
CHANGE in the stream water over
a 24 hour period
< 2 oC/ 24 hr good, 2-5 oC/24 hr fair,
> 5 oC/24 hr poor
Since water has a great heat holding capacity (from its high specific heat)
temp. shouldn't change very much from day- night. A constant temp. > 18 oC
is deleterious to aquatic life
Heavy Metals
(Toxic)
The measurement of lead, arsenic,
copper, cadmium, cyanide,
mercury, and other man-made
compounds in water
The following numbers reflect DRINKING water standards (in
mg/L): Lead 0 , Arsenic 0, Copper 1.3, Cadmium 0.005,
Cyanide 0.2, Mercury 0.002, Benzene 0, Dioxin 0, PCB's 0
Miniscule amounts (in ppb) of these chemicals cause a variety of human
problems ranging from liver kidney, neurological, and reproductive damage.
Problems for aquatic animals has not yet been determined for most of them.
Fecal Coliform
The measure of E. coli bacteria (in
colonies present/ 100 ml sample)
of water
Number of allowable colonies/ 100 ml sample of water:
Drinking water -- 0, Swimming -- 100,
Boating/Fishing -- 1000
E. coli, a harmless bacteria, is found in the digestive tract of warm blooded
animals along with pathogenic bacteria that might be in the fecal material.
The presence of E. coli shows that fecal material is present in he water and
might be harboring those pathogens.