The Laramie Basin - Mountains and Plains: The Ecology of Wyoming Landscapes - page 296

Modern
Laramie
River
floodplain

Dissected
bench with
Pleistocene
overwash

Little
Laramie
River
terrace

Modern Little
Laramie River
floodplain

Pleistocene
floodplain-
Airport Bench

Eolian deflation
basin- Big Hollow

Dissected
bench

Laramie River
terrace

7,500

7,400

7,300

7,200

7,100

Northwest Southeast

7,000

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000

Distance along profile, feet

Riparian Upland

grassland

Not
vegetated,
playa

Irrigated
hayland

Upland
grassland
Riparian

Upland
grassland

Upland
grassland,
hayland

Upland
grassland

Fig. 17.15. Seventeen-mile profile across the Laramie Basin
with topographic features and land cover indicated. As
shown in figs. 17.1, 17.3, and 17.7, this long profile extends
southeastward from the Little Laramie River, where a mosaic
of riparian woodlands, shrublands, meadows, and irrigated
hayland can be found. Grasslands are found over most of the
upland, across the Airport Bench, and down the slopes to near
the bottom of Big Hollow, where a playa with an ephemeral
pond has formed. there is no drainage from Big Hollow, but
standing water is rare because of low precipitation and no
streamflow. the Airport Bench is a remnant of the valley
floor at an earlier phase in the excavation of the basin and
has a surface that has been armored by coarse river cobbles

deposited during the Pleistocene. From the Big Hollow playa
southeastward, grasslands are found on the slopes and top
of a dissected bench. Beyond that, the former floodplain of
the Big Laramie River, known as a terrace, has a mosaic of
grasslands, shrublands, and irrigated hayland. Several lakes
also are located in this area. Riparian vegetation is found in
the current floodplain of the Big Laramie River. the profile
terminates on the dissected margins of a third, more ancient,
erosion-deposition surface. the Harmony Bench, illustrated in
fig. 17.5, does not occur along this profile. Plant species com-
position is influenced by topography, varying soil characteris-
tics, and exposure to wind.

sources of water and railroad stockyards (fig. 17.17).
Wolves were eradicated, enabling coyotes to become
more abundant. Prairie dog densities declined; down-
cutting of stream channels accelerated.
equally profound change resulted from the establish-
ment of irrigation systems, beginning in the 1870s. 24 the
broad floodplains of the Big Laramie and Little Laramie
rivers enabled flood irrigation (see figs. 17.1 and 17.7).
Dams, canals, and ditches eventually were developed,
including the Wheatland reservoirs on the Laramie
River. Some of this irrigated land, though a small pro-
portion of the basin floor, was originally tilled for crops,
eliminating the native vegetation, but this practice soon
proved uneconomical because of the cool, short grow-
ing season. Livestock production prospered; irrigated
hayland—now with mostly introduced species—became
a valuable commodity.

irrigation had two general effects. First, it disrupted
the streamflow patterns of the rivers and creeks, reduc-
ing flood peaks in the spring and emptying many
streams by late summer, when irrigation water was in
greatest demand. Second, it enlarged the area of land
that was flooded. essentially all floodplains and some
adjacent uplands were altered by this practice. in gen-
eral, native riparian woodlands and shrublands exist
today only on land that was too wet for domestic use,
or where the presence of native plants provides benefits
appreciated by the landowners, such as shade for live-
stock, erosion control, shelter for homes and barns, or
habitat for fish and wildlife.
today the glint of numerous lakes across the basin is
especially obvious at sunset from the crest of the Lara-
mie Mountains—all more or less permanent because of
their connection to irrigation systems and providing