Monday, September 28, 2009

What Causes Deep Penetration Of Uv Light In Lakes

Ultraviolet light effects a lake's environment.








Ultraviolet (UV) light is part of the light spectrum that is unseen to the human eye. As it reaches the earth it impacts the environment in many ways. Like other light waves, when UV light strikes water, it disperses and eventually disappears. How far it penetrates a body of water, such as a lake, before it is totally dispersed, depends upon many factors.


Lack of Suspended Particles


Ultraviolet light leads to clear water.


One lake where UV light reaches deep is Crater Lake in Oregon. According to the Crater Lake Institute, studies there have shown that UV light has penetrated to a depth of 320 feet, which is the deepest known penetration of any lake in the world. This deep penetration makes the water of Crater Lake crystal clear, which is the chief attraction of the lake. The research at the Institute has concluded that it is the lack of suspended particles in the surface water that allows the UV light to reach the great depths. In most lakes, those particles absorb the UV light on or near the surface, thus preventing the UV light from reaching into the depths of the lake. The Biology Encyclopedia also confirms that dissolved organic carbon controls how far UV light penetrates.


Few Phytoplankton


At Crater Lake it has been determined that there is a near absence of phytoplankton on or near the surface of the lake. This lack of phytoplankton gives the lake it beautiful blue color, and allows the UV light to penetrate deep into the lake, as the phytoplankton are not there to absorb the UV light. According to the studies by the Crater Lake Institute, this condition has continued since the lake's discovery in the 1800s.


High Elevation








A study by the Center for Lakes and Reservoirs at Portland State University in Oregon concluded that high elevation of a lake, in this case Waldo Lake with an elevation of 5,400 feet, lead to the deep penetration of UV light. This effect had the same result as with Crater Lake, a lake with very clear water and little plant life on or near the surface, due to the UV light.

Tags: Crater Lake, near surface, Ultraviolet light, absorb light, allows light, clear water, concluded that