PUB00095

• Year: 1988
• Title: Colorado Water
• CWCB Section: Administration
• Author: League of Women Voters of Colorado
• Description: A publication to present facts, background and issues regarding water in Colorado.
• Publications - Doc Type: Other

Geographical Characteristics

major factor in the early settling of the state and
its economic development.
Colorado's western plateau region is
characterized by high tablelands or mesas and
deep canyons. As a whole, this is a region of
flat-lying sedimentary rock, more than a mile
above sea level. The Colorado River and its
tributaries expose many layers of sandstone,
limestone, mudstone and shale as they cut their
way to lower altitudes. The sandblast effect of
the winds and the scouring action of the waters
have created scenic sculptures in the rock
formations.. The Colorado Plateau is rich in
minerals; placer gold, uranium, oil and gas, and
extensive deposits of oil shale.

HYDROGEOLOGY

."'Hydt~ogy'is.the-geoklgy'.of'1}roond"'-'"
water. I nvestigation shows that underground
formations which are factors in the storage of
ground water do not necessarily correspond
with surface characteristics.
Presence of water in a particular area
depends on the interrelationship of climate,
geology and topography. The moisture of rain or
snow usually remains at its original location only
briefly. Much of it evaporates. If it falls on level
land with porous soil much of it will soak into the
ground there, but on a rocky slope most of the
water will run off to a more receptive location.

This is the surface water. Of the water which
remains on the surface, a large portion is lost
through evaporation.
That which soaks into the ground and is
not quickly taken up by the roots of plants tends
to seep downward until it reaches the barrier of
a non-porous formation. This is the ground water.
An aquifer is an underground layer,
primarily of sand, gravel or porous rock, through
which water can move easily. It is confined by
less permeable rock which holds in the collected
water. Aquifers sometimes lie between layers of
soil, shale or other materials. Aquifers may be
several hundred feet thick or very thin layers.
They may be hundreds of miles wide or cover
only a small area. If extensive and prolonged
withdrawals of water occur, the level of water is
lowered unless the aquifer is recharged, either
...,~>:: na..W-':~I?.2~~"~~ 0~!?X~~~~9n!1.a!1.!.!IY~Ls".
The speed at which an aquifer refills is known as
its recharge rate. The movement of ground water
is usually very slow, so the normal recharge rate
is likely to be quite slow. Some of Colorado's
aquifers have taken thousands of years to build
up, but modern wells can pump them out much
faster than their recharge rate. This is called
mining of groundwater. Groundwater which has
collected in an aquifer can be tapped and
brought to the surface by means of wells, or
there may be a natural opening from the aquifer
to the surface, producing a spring.

The main source of agricultural well water
is the alluvium (unconsolidated sand and gravel)
associated with major rivers. Water within the
alluvium of a stream is linked with the surface
flow. Sedimentary rock, such as sandstone,
possesses water-bearing capabilities, but may
not always contain water. This is the type of
formation which underlies much of the state. In
some areas it is on or near the surface while in
other regions it lies 8,000 feet below the surface.
Some sections provide a good quality water
while others are contaminated with salts and
hydrocarbons. The water found in the
sedimentary rock formations has, as a rule, very
little relationship to surface flow, either as to
supply or location. Most of the mountains are
underlain with a hard, non-porous rock such as
granite. Water passes through or is stored only
in the fractures of these formations. Much less is
. . known about the hydrog~ology of granite r()ck
'."fIlai'ii'SKriowi'rregardlng"'"'ffieseaTiiientary"rocriif'.
alluvium.
Because the underground layers of earth
are variable and difficult to ascertain, extensive
exploration is necessary to obtain accurate
information concerning the quantity and quality
of the available water. There may be
considerable difference in neighboring counties
or even within a county. It is possible that a large
supply might be found. It is also possible that in
certain areas the aquifer could be recharged and
the water held for future use. Without question it
is a field in which research is needed.

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