Colorado State Water Plan 1974 ‎(Phase I)‎

• Year: 1974
• Title: Colorado State Water Plan
• CWCB Section: Agency-wide
• Publications - Doc Type: Historical

General Description of the Environment
Structurally the Great Plains is a large basin with part of Colorado being
situated on its western edge. The Great Plains area of Colorado is subdivided
into the Colorado Piedmont, High Plains, and the Raton Section. The Colorado
Piedmont, which butts against the mountains, is elevated and dissected, the
South Platte and the Arkansas Rivers being the main drainages. These rivers
and some of their tributaries have been the primary agents in the evolution of
this large elevated area which is now a rolling plain with a thin mantling of
unconsolidated materials overlying shale and occasional limestones and sandstones.
The High Plains, occurring at the eastern limit of Colorado, consists of
erosional remnants of fluvial plains formed by outwash from the Rockies. The
material forming these fluvial deposits is largely silt with varying amounts of
sand and gravel. The material is generally unconsolidated but local lime
cementation is common.
The Raton section, occurring at the southern edge of Colorado, is underlain
by the same sedimentaries as the Colorado Piedmont. However, the high mesas
that are characteristic of this section are usually capped with volcanic flows.
Three of the six subdivisions of the Colorado Plateau extend into south-
western Colorado. The main distinguishing features of this province are
horizontal lying sedimentary strata, the high elevation of the entire plateau, and
numerous steep canyons.
The Uinta Basin subdivision, an area of deeply dissected plateaus and
badlands, lies just south of the Uinta Mountains. The lava-capped Grand Mesa
marks the southern limit of this subdivision.
The Canyon Lands subdivision is south of the Uinta Basin. The Canyon Lands
of western Colorado are not typical of this subdivision as the Gunnison, Colorado,
and Uncompahgre Rivers have formed broad valleys in the sedimentary beds as
compared to the narrow deeply entrenched canyons they have created further west.
Several large plateaus, such as the Uncompahgre and Mesa Verde, are defined by
the wide river valleys.
The third subdivision is the Navajo Section which occupies a very small
portion of southwestern Colorado along the headwaters of the San Juan River.
Here, the predominant rock is sandstone with lesser amounts of shale. Inasmuch
as the beds dip slightly, the forces of erosion that are associated with the arid
climate have created an abundance of mesas, cuestas, rock terraces, retreating
escarpments, and dry washes.
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