Geoscience Reference
In-Depth Information
Mountains (High Plains Regional Climate Center
2011). This precipitation gradient is rel ected in
the transition from tallgrass prairie in the east,
to mixed-grass prairie, to shortgrass prairie in
the west. Great Plains climate is continental and
highly seasonal. In the southern plains, summers
are long and hot, and winters are short and cool.
The northern plains are the opposite; the great-
est temperature contrast occurs in the northern
plains where summer maximum may exceed
40 °C and winter minimum may dip below
Oklahoma, eastern New Mexico, southwest-
ern Kansas, and southeastern Colorado.
They are dry much of the time, but turn into
rich marsh and ephemeral lake habitats
during wet years.
16.2.1 Upper Arkansas River valley,
Colorado and Kansas
The Arkansas River begins in central Colorado
on the Continental Divide surrounded by peaks
that exceed 14,000 feet (
−
40 °C.
A tremendous variety of wetland types exists
within this vast territory. Toward the east, water
is abundant and wetlands are mostly perennial
and fresh. In contrast, precipitation declines
westward and alkali water chemistry pre-
dominates, except for rivers draining the Rocky
Mountains. Western wetlands are more subject
to droughts and periodic dry conditions. Great
Plains wetlands occur in four main geologic
settings:
4260 m) elevation. It
descends through the Royal Gorge (Fig. 16-1),
l ows across the High Plains of southeastern
Colorado, and continues into southwestern
Kansas. Along the way, every drop of water
derived from mountain snowmelt and summer
thunderstorms is extracted for human use (see
Fig. 1-8). Human diversion of water begins in the
mountains with irrigation for cattle grazing and
hay production in wet meadows (Fig. 16-2).
As the Arkansas River leaves the mountains,
it is contained in Lake Pueblo (Fig. 16-3). Lake
Pueblo and the Pueblo Dam were constructed
by the U.S. Bureau of Reclamation as part of the
Fryingpan-Arkansas Project, in which waters
are diverted from the western slope of the Con-
tinental Divide and transferred down the Arkan-
sas River to the southeast. Lake Pueblo is the
principal storage reservoir in the project. Its
waters are used for irrigation, drinking and rec-
reation, and it provides l ood control to the
Pueblo community.
Across southeastern Colorado, water is
extracted from the Arkansas River to support
irrigated agriculture (Fig. 16-4). Water is diverted
via canals directly to irrigated i elds and into
reservoirs in tributary valleys, from whence the
water is further distributed to agricultural i elds.
These reservoirs have become wetlands with
hydric vegetation, abundant i sh, and migrating
waterfowl (Fig. 16-5). As the Arkansas River
passes into Kansas, only a small stream remains
as required by the Kansas-Colorado Arkansas
River Compact and afi rmed by the U.S. Supreme
Court (Kansas Department of Agriculture 2010).
The vicinity of Lakin-Garden City is most
instructive (Fig. 16-6). Water extraction takes
place via canals into i elds and holding
>
• Glaciated terrain - Recently glaciated regions
have abundant undrained or poorly drained
depressions, channels and potholes of all
sizes and shapes. This region includes
parts of the Dakotas, Iowa, Minnesota and
Montana, and most of the Canadian Prairies.
Older glaciated regions to the south are
more eroded and do not support so many
wetlands.
• Sand hills terrain - High water tables and
good ground-water recharge make sand
hills prime candidates for wetlands in the
swales and basins between dunes. Good
examples include the Nebraska Sand Hills
and the Great Sand Hills of southwestern
Saskatchewan.
• River l oodplains - Large and small river
valleys have in many regions broad l ood-
plains that contain wetland habitats. The
Missouri River and its many tributaries drain
most of the northern Plains. Other major
drainages include the Red River, Saskatch-
ewan River, and Arkansas River.
• Playas - Shallow wind-eroded depressions
are found primarily in the southern High
Plains, particularly western Texas and
