Geoscience Reference
In-Depth Information
Figure 16-29.
Satellite image of the Missouri Coteau, southern Saskatchewan, Canada (see Color Plate 16-29). Dirt
Hills and Cactus Hills are large ice-shoved ridge complexes. Old Wives Lake and other water bodies are full during
a wet episode. Active vegetation appears in green and yellow-green colors. Landsat TM bands 1, 5 and 7 color
coded as blue, green, and red; image date 9 September, 2002. Image from NASA; processing by J.S. Aber.
and higher ground to the south. During
deglaciation, the size, shape and volume of
such proglacial lakes changed frequently as
outlets were eroded and the ice margin
retreated northward. Old Wives Lake illus-
trates this type of wetland setting (see Color
Plate 6-29).
Water quality tends to be quite hard
(dissolved calcium and magnesium) due to
abundant limestone and dolostone in glacial
sediments. Many shallow lakes and wetlands
become eutrophic during the summer and
support large algal blooms, which are enhanced
by runoff of fertilizer from agricultural i elds.
Alkali chemistry is found in many lakes of the
Palliser Triangle and adjacent United States (Fig.
16-34). Sodium sulfate is present both in the
brine and in salt deposits, mainly as the mineral
mirabilite (Glauber's salt). Sodium sulfate has
been produced commercially from some of
these lakes for various industrial applications
-
manufacturing pulp and paper, replacement for
phosphate in detergent, pollution control at
coal-i red power plants, and other purposes
(
Encyclopedia of Saskatchewan
2006a). For
example, Frederick Lake was the site of a salt-
processing plant using saline water diverted
from Old Wives Lake, especially in the 1950s
and 60s (
Encyclopedia of Saskatchewan
2006b),
but the plant is now abandoned. Salt extraction
The Missouri Coteau is part of the Palliser
Triangle region of southern Saskatchewan and
southeastern Alberta, which represents the
driest portion of Canada (Sauchyn 1997). This
region is characterized by brown soils, tempera-
ture extremes, and a water dei cit; yet it is agri-
culturally one of the most important regions in
Canada for production of wheat, canola, l ax,
and other grain crops. The continental climate
of the Palliser Triangle is subject to wet and dry
cycles over periods of decades and longer
time intervals. Droughts are common events his-
torically. Thus lakes and wetlands may i ll and
overl ow at times and completely dry up at
other times (Fig. 16-33).
