BOARD01250

• Board Meeting Date: 12/9/1964
• Description: Minutes
• Board Meetings - Doc Type: Meeting

I

water bearing sand and gravel and is one of
the controls on the water level in these
deposits, and during much of the year drainage
from these deposits sustains the flow of the
river. In fact, the ground water body is there
largely because of diversion for irrigation
from the river. The ground water reservoir is
recharged by applied irrigation water and by
precipitation. However, only a part of the
precipitation reaches the water table; the
rest is consumed by plants or evaporated. The
ground water that is not pumped, evaporated
or transpired ultimately seeps to the Arkansas
River.

The amoUnt of water that now returns to
the river has been diminished because of the
large scale development of irrigation wells.
Most of the wells have been drilled since
World War II, and their number has more than
doubled in the past 10 years. There are
about 1,460 large-capacity irrigation wells
pumping in the Arkansas valley and these
wells, of course, as Mr. Sparks has pointed
out, are shown on these maps (again pointing).
The amount of ground water pumped, for example,
in 1950 in the Arkansas Valley was about 31,000
acre-feet; in 1964 230,000 acre-feet was pumped.

I

Now if you'll turn your attention please.
to the drawings to my left, a pilot study of
a short reach of the Arkansas River between
the towns of La Junta and Las Animas, a 25-
mile reach of the river, has shown that an
increased use of the ground water reservoir
has been a major factor in the reduction of
return flow to the river. The records for
ground water and surface water use for the
period 1940 to 1960 were analyzed. The figure
to my far left (pointing), this figure here,
is a graphic representation of the trends of
ground water pumpage, phreatophyte use, and
surface water return flow. Surface water
return flow is shown in red, ground water
pumpage is shown by the black dash line and
the phreatophyte use trend is shown by the
green dash line.