Geoscience Reference
In-Depth Information
A
B
Figure 3-26.
Permanent gauging station on the upper Missouri River at Culbertson, Montana, United States. A.
Cable (
∧
) supports a manned carriage for measurements of depth and velocity across the channel. The carriage
comes from the far side (*). B. Closeup view of manned carriage that rides across the cable. U.S. Geological Survey
gauging station 06185500 in operation since 1941; current and historical data online (http://nwis.waterdata.
usgs.gov/nwis).
Color is an important attribute of wetland
soils, as noted above. Color vision is among the
most important human senses, and a great deal
has been written about human perception of
color both from the aesthetic and technical
points of view. A full discussion of color is well
beyond the intent of this topic, so only a few
basic aspects are presented here. For a good
discussion of color in nature, see Lynch and
Livingston (1995). Several means exist to dei ne
color quantitatively. One approach is based on
the proportions of primary colors (blue, green,
red) and their intensities, which applies to
digital photography, color monitors, and human
vision (e.g. Drury 1987).
Another well-established means for dei ning
color is the Munsell Color system, which is
based on three attributes of color that are often
illustrated in a wheel diagram (Fig. 3-28). It is
widely used in the natural sciences for describ-
ing soil and rock colors (Fig. 3-29).
Figure 3-27.
Portable, automatic, solar-powered
weather station operating at an artii cial wetland site
for passive treatment of contaminated ground water. All
conventional meteorological factors are measured for
site and regional weather monitoring and analysis.
Photo by J.S. Aber at Commerce, Oklahoma, United
States.
• Hue - actual spectral color such as red,
yellow, green, blue, etc. Hue is designated
by a number and letter.
• Value - lightness or brightness of the color.
Value ranges from zero for pure black to 10
for pure white.
• Chroma - intensity or saturation of the color.
Chroma begins with zero for neutral (gray)
and increases with no set upper limit.
by meteorological means (Fig. 3-27). Measuring
underground water movement is much more
complicated and requires monitoring wells and
some knowledge of the aquifer characteristics
(see below).
