BOARD01250

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

""i'..L.G.G

In the 1940's the average ground water
pumpage between La Junta and Las Animas was
about 1,200 acre-feet per year; in the 1950's
11,000 acre-feet per year was pumped on an
average; and in the first half of the 1960's
25,000 acre-feet was pumped. The year of
greatest pumpage was this year, 1964, when
29,700 acre-feet of water was withdrawn from
the aquifer. On the other hand, the return
flow to the Arkansas River was reduced by
something on the order of 20,000 acre-feet
from 1940 to 1963. This is shown by the red
line and it is obvious that the red line and
the black line correspond quite closely. The
similarity of the trends is therefore apparent.
A significant cause of the reductions of return
flow is the increased pumpage of water by wells.
However, phreatophyte growth has increased
over this same period and has caused a part
of the reduction in the return flow. Phrea-
tophyte use, as I said before, is shown by
the green line. Additional causes for in-
creased demands or decrease in surface water
return flow may have been improvements in
agricultural practices.. The irrigation well
development in the Arkansas Valley has been
beneficial in that the wells provide water to
crops during times of deficient surface water
supply. However, these wells were drilled and
were used with little evaluation of their
effect on the surface water supply.

In order to minimize adverse effects and
to achieve maximum use of the available water
supply, ground water and surface water must
be developed and managed as a single supply,
but development and management cannot be
planned properly until the operation of the
hydrologic system is quantitatively described.

The U. S. Geological Survey, in coopera-
tion with the Colorado Water Conservation Board
and the Southeastern Colorado Water Conservancy
District, is studying the Arkansas Valley in
order to evaluate the hydrologic system so
that the effects of selected changes in water
management can be predicted. Because of the

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