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Big Laramie
River floodplain
Chugwater
Formation
Tertiary
alluvium
Chugwater
Formation
Forelle
Limestone
Satanka
Shale
Casper
Formation
7,600
7,400
7,200
West
East
7,000
0
5,000
10,000
Distance along profile, feet
15,000
20,000
Riparian
meadow,
shrubland
Meadow,
upland
grassland
Not
vegetated,
landfill
Riparian
meadow
Upland
grassland,
sagebrush
Riparian
meadow
Sagebrush,
mtn.-mahogany
Foothill
shrubland
Upland
grassland,
sagebrush
Fig. 17.16. Four-mile profile just north of Laramie, from the
Big Laramie River into the foothills of the Laramie Moun-
tains, illustrating topographic features and land cover (see
figs. 17.1, 17.3, and 17.7 for location). toward the east, beyond
the riparian meadows and shrublands, the surface slopes up
onto red beds of the chugwater Formation. this rock is more
resistant to erosion than most materials in the middle of the
Laramie Basin, but the sloping surface has been altered by
erosional processes. At about 8,000 feet along the profile,
alluvial materials from higher slopes cover the chugwater.
Soil development throughout this area is sufficient to support
grasslands. the portion of the profile lacking vegetation is the
Laramie Landfill. A narrow riparian meadow is intercepted
just beyond the landfill, where the profile crosses the bed of
an ephemeral stream. the steeper Forelle Limestone then
rises to a more pronounced hogback ridge with shallow soils
supporting foothill shrublands. the ridge is sharply defined
because of erosion of the underlying Satanka Shale beds to
the east. the profile ends on the slope of the casper Forma-
tion, which extends to the crest of the Laramie Range—the
hydrologic boundary of the basin. the lowest outcrops of the
casper Formation mark the boundary of the valley floor for
much of the eastern side of the basin. Grasslands are char-
acteristic of deeper soils developed over the chugwater and
Satanka formations; shrublands with mountain-mahogany,
Rocky Mountain juniper, black sagebrush, and wild currant
are found on the ridges of the Forelle and casper formations.
the casper Formation is a very important aquifer, as dis-
cussed in the text, and its limestone strata are an important
source of calcium carbonate for the local cement plant.
wetlands that are important for wildlife (see chapter
that previously flowed out of the basin, spreading water
across the lower, flatter parts of the landscape, thereby
producing better-watered ecosystems than had existed
previously. Water withdrawals modified the rivers, but
irrigation waters that contributed to the formation of
wetlands appear to have increased biological diversity
in the basin as a whole. introduced trout still thrive in
the rivers, as they do in the lakes that had been created
or enlarged. As noted, congress designated some associ-
ated wetlands as national wildlife refuges. Some species
clearly benefited from wetlands maintained with irriga-
tion projects, including mosquitoes.
26
A conundrum has now developed that connects Wyo-
ming wetland habitat—and the endangered Wyoming
toad—with wetlands in nebraska, where there are four
endangered species—the whooping crane, piping plo-
ver, least tern, and pallid sturgeon. the nebraska species
depend on adequate water in the Platte River, of which
the Laramie River is a tributary. Potentially, more irri-
gation upstream in Wyoming, or more severe droughts
anywhere in the watershed, could reduce the amount
of water downstream. For whatever reason, if more river
water is required to maintain viable populations of the
endangered species in nebraska, the Platte River com-
pact and other regulatory statutes could require more
could reduce water availability for Wyoming wetlands.
can irrigation systems be engineered to use water more
efficiently and so enable survival of the nebraska endan-
gered species without leading to the decline of Wyo-
ming's endangered species? that challenge would be
especially difficult if climate change leads to extended
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