Geoscience Reference
In-Depth Information
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B
Figure 4-3.
Overview of Dry Lake, an ephemeral lake at the terminal point of an enclosed basin on the High
Plains in west-central Kansas, United States (see Color Plate 4-3). A. May 2007, a wet year with the lake full of
water; note small overturned row boat in lower left corner for scale. B. May 2008 displays a wet mudl at
surrounded by salty soil. Similar views toward the southwest; kite airphotos by S.W. Aber and J.S. Aber.
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Figure 4-4.
Tidal effects on Rowley River and salt-marsh complex in northeastern Massachusetts, United States. A.
Morning high tide. Rowley River and smaller tributaries are full. B. Afternoon low tide. Note exposed mudl ats. The
river is much narrower and some smaller channels are nearly drained. Tidal ebb and l ow generate noticeable
currents in the channels. Blimp airphotos by S.W. Aber, J.S. Aber, and V. Valentine.
and tend to rel ect seasonal patterns in precipi-
tation and snow melt. Wooded swamps are typi-
cally associated with larger river systems and,
thus, also follow seasonal water supply from the
entire drainage basin. These hydroperiods are
more predictable.
Water enters a wetland with certain physical,
chemical, and biological properties. Physical
properties are temperature and turbidity, which
is the content of suspended i ne sediment
(mud
solids or compounds. Biological properties refer
primarily to microorganisms, namely bacteria
and viruses, as well as other plants and animals
(Fig. 4-6). As the water moves through a wetland,
all of these properties may be altered by physi-
cal, chemical, and biological processes within
the wetland environment. Residence time is a
measure of how long it takes a parcel of water
to move through the wetland, typically weeks,
months or years for many wetlands. Longer resi-
dence times allow substantial modii cations in
water properties to occur. Human structures
-
ditches, canals, drains
-
that reduce residence
clay) particles. Chemical proper-
ties include salinity, acidity (pH), oxidation
potential (Eh), hardness, and other dissolved
=
silt
+
