*Lake Color information pages are currently in draft form.

What is it?
Suspended and dissolved particles in water influence color.  Suspended material in lake water may be a result of natural causes and or human activity. Weathered rocks and soils, the land-use activity and the type of trees and plants growing within the watershed will influence the types and amount of dissolved and suspended material found in a lake or stream.

Photo: GMC
This picture was taken looking down into a relatively clear lake. Lakes like this let light through the water to greater depths, allowing increased plant growth on the bottom. The color of this lake water may be a result of the geology, land use and biological processes happening around this lake, combined with the biological processes at work in the lake. The blue color in the picture is from reflection of the sky above.

An example of human impact on water color is when farms or construction areas have large areas of exposed soil which are easily eroded by water and weather, and rain or snow melt cause large volumes of the soil to flow downhill, eventually into a lake and create a muddy brown color.

Dissolved Organic Carbon
The amount of "color" in a lake may be affected by the concentration of natural dissolved organic acids such as tannins and lignins, which give water a tea color. Dissolved Organic Carbon (DOC) is used to describe the thousands of dissolved compounds found in water that come from organic materials such as decomposed plant matter. Some DOC molecules have a recognizable chemical structure that can easily be defined (such as fats, carbohydrates, and proteins) however most are hard to identify by their structure, and are lumped under the term humic or tannin substances.

Photo: GMC
The picture above is of Newbert Pond. Newbert is located in a boggy area rich in organic matter. Water flows through this debris and leaches out tannins and lignins, which color the pond. This process is often compared to making a cup of tea.

The more recognizable types of DOC such as soluble fats, proteins, and carbohydrates are often created within the stream or lake from animal feces or decomposition of fish and insects.  This type of DOC is not pigmented and does not influence the color of a lake or stream. 

However, humic or tannin DOC, do have an effect on the water color of a lake. This type of DOC is formed when plant material is slowly broken down by organisms into very small particles that are dissolved into water. This process does not usually happen in a stream or lake, but in a place such as a wetland, and ends up washing into the lake. These substances often have natural acids which can influence pH levels. Tannins that are yellow to black in color are the most abundant kind found in lakes and streams and can have a great influence on water color.

Lakes that are surrounded by coniferous forests (evergreens such as pine, spruce, hemlock and fir trees) are generally brown in color because pine needles that fall to the ground (called litter) are very slow to degrade. This is also true of lakes surrounded by wetlands, where plants decompose very slowly.

Photo:GMC
Lakes that are surrounded by wetlands, like the one pictured above, are likely to have a brown color because of inputs of slowly decomposing plant material from the wetland.

Resources:
Bronmark, Christer and Lars-Anders Hansson. 1998. The Biology of Lakes and Ponds. New York. Oxford University Press.