It may surprise you to learn that several sandstone formations supply
water to artesian wells northeast of the Monument in The Redlands,
Orchard Mesa, and the southwestern side of the Grand Valley, most of
which are 500 to more than 1,000 feet deep. When first drilled and for
some years later these wells flowed at the land surface, but eventually
after too many wells had been drilled too close together, each well
reduced the output of neighboring wells until most wells ceased to flow
naturally. This made it necessary for most well owners to install pumps,
which further aggravated the problem by reducing the artesian head (the
height to which the water rises above the formation from which it
issues). This created a situation not unlike too many children sucking
on straws in the same ice cream soda, and led to a detailed
investigation by the U.S. Geological Survey and the Colorado Water
Conservation Board,[16] outgrowths of which were the present report and
its predecessors.
The water system of the Ute Conservancy District was virtually completed
by late 1964 and began to supply water to rural residents of Grand
Valley between the towns of Palisade and Mack through a vast network of
pipelines. The water is obtained from surface sources on the north flank
of Grand Mesa east of the valley and is brought to the valley via a
pipeline down the valley of Plateau Creek. Use of the new water has
reduced the draft on many of the artesian wells. The reduced draft has
locally arrested the decline in the artesian head or has actually
allowed some recovery in head.
In order of their importance and productivity the water-bearing
sandstones are the Entrada, the Wingate, and local sandstone lenses in
the lower part (Salt Wash Member) of the Morrison Formation (fig. 7). In
a few places small flows or yields are obtained from wells that tap the
Dakota Sandstone and underlying Burro Canyon Formation, but inasmuch as
the Dakota contains some marine sandstones from which all the salt
seemingly has not yet been flushed out, the water from most of these
wells is brackish or salty.
As we will see on the trip “From Grand Junction through The Redlands to
the West Entrance of the Monument,” pages 88-95, in and near the
Monument these sandstones look bone dry, so how can they supply water to
artesian wells? They are indeed dry in all the cliff exposures, but as
will be noted later when the bending and breaking of the rocks are
discussed (p. 64-71), erosion has exposed the upturned sandstones so
that they may take in water from the many small streams that drain the
Monument and adjacent areas for short periods after summer
thundershowers or during spring thaws. The water moves slowly down the
dipping sandstones and becomes trapped under pressure beneath overlying
beds of siltstone or mudstone—materials that are nearly impervious.