home home lake superior communities understanding
the streams
citizens and schools
  Watersheds     Water Quality Primer     Water Quality Impacts      Organisms     Water and Wastewater     Landscape

Stream Anatomy — Overhead Canopy

Overhead canopy is a measurement of the extent to which the stream itself is overhung and shaded by trees, bushes, and tall grass. These plants can contribute shade and cover for fish and wildlife and can provide the stream with needed organic material such as leaves and twigs. This shade (or overhead canopy) provides several important functions in the stream habitat. The canopy cools the water; offers habitat, protection, and refuge for aquatic organisms; and provides a direct source of beneficial organic matter and insects to the stream.

Lawns in a stream's riparian zone may indicate that pesticides and grass clippings are a possible problem, and that little habitat and shading are available. Bare soil and pavement might indicate problems with erosion and runoff.

Canopy has been widely acknowledged as influencing stream temperature. Complete removal of riparian vegetation can elevate stream temperatures.

open canopy
closed canopy
These two images were taken though a hemispherical or fish eye lens looking above forested wetlands.
This technique is used to measure the extent of the forest canopy.