Color
Suspended and dissolved particles in the water
influence color. Suspended material can be from both natural
causes and human activity.
Weathered geologic material, vegetation
cover within the watershed, and land-use activity will influence the
types and amount of dissolved and suspended material found in a lake or
stream. An example of human impact on water color is when farms or construction areas have a lot of soil
erosion. Rain or snowmelt can cause large volumes of soil to
flow into the water and create a muddy brown color.
The amount of "color" in
a lake can refer to the concentration of natural dissolved organic acids
such as tannins and lignins (see explanation of Dissolved Organic
Carbon), which give water a tea color.
Color is measured by
comparing a sample of the lake water to Standard Platinum Units (SPU).
Lakes that are considered colored (>25 SPU) can have reduced
transparency readings and increased phosphorus values. This does not
mean the lakes are more productive, the color simply interferes with the
test so better results can not be achieved. Chlorophyll a (Chla)
is the best indicator of productivity in colored lakes and should be
used if possible (see explanation of
Chlorophyll a). Color varies from 0
to 250, with the average in Maine being 28 SPU.
 |
Clear lakes allow
more light through the water, allowing increased plant growth on the
bottom. Rocks, algae, and plants will absorb and reflect light,
influencing color. Blue color is from reflection of the sky above. |
Care to Compare?
The data used to create this graph were provided
to PEARL by the Maine Department of Environmental Protection
(DEP). DEP summary data were
used, which can be viewed by clicking "Browse Data Sets" then
the "Water Quality" button from PEARL's homepage. The distribution of mean (or
average) color recorded at 962 sampling sites are shown. Need data? You
can search for a lake or pond from
the PEARL hompage.
Out of 962 sample stations:
|
Color reading in Standard Platinum
Units |
Number of sample sites with
readings in this range |
Percentage of sample sites with
readings in this range |
|
0 - 9 |
85 |
8.9 |
|
10 - 19 |
339 |
34.8 |
|
20 - 29 |
239 |
24.8 |
|
30 - 39 |
139 |
14.4 |
|
40 - 49 |
63 |
6.5 |
|
50 - 59 |
39 |
4.1 |
|
60 -69 |
22 |
2.3 |
|
70 - 79 |
12 |
1.4 |
|
80 - 89 |
9 |
0.9 |
|
90 -99 |
5 |
0.5 |
|
≥100 |
14 |
1.4 |
- 85, or 8.9%, had color readings of 0 -9 SPU
- 339, or 34.8%, had color readings of 10 - 19
SPU
- 239, or 24.8%, had color readings of 20 - 29
SPU
- 139, or 14.4%, had color readings of 30 - 39
SPU
- 63, or 6.5%, had color readings of 40 - 49 SPU
- 39, or 4.1%, had color readings of 50 - 59 SPU
- 22, or 2.3%, had color readings of 60 - 69 SPU
- 12, or 1.4%, had color readings of 70 - 79 SPU
- 9, or 0.9%, had color readings of 80 - 89 SPU
- 5, or 0.5%, had color readings of 90 - 99 SPU
- 14, or 1.4%, had color readings of ≥100 SPU
|
