The Objective of the observation-well program in Nebraska is to
provide an evaluation of the status of the ground-water supplies.
Many uses tor water-level data are known but not all potential uses
can be foreseen. Among the important uses are the following:
(1) To indicate the status of ground water in storage or in
transit and the availability or supplies.
(2) To show the trend of ground-water supplies and the outlook
tor the future.
(3) To estimate or forecast the base flow of streams.
(4) To indicate areas in which the water level is approaching
too close to the land surface (water-logging) or is receding toward
economic limits of lift or toward impairment by water of poor quality.
(5) To provide long-term evidence for evaluating the effectiveness
of land-management and water-conservation programs in relation to
water conservation actually effected, and for use in basin or "watershed"
(6) To provide long-term continuous records to serve as a framework
to which short-term records collected during intensive investigation may be related.
The water level in an observation well functions as a gage to
indicate the position or the water table. The water table is defined
as the upper surface of the zone of saturation except where that
surface is formed by overlying impermeable materials. The water
table is also the boundary between the zone of saturation and the
zone of aeration. It is not a level surface but is a sloping surface
that has many irregularities, and it often conforms in a general way
to the land surface. The irregularities are caused by several
factors. In places where the recharge to the ground-water reservoir
is exceptionally large, the water table may rise to form a mound from
which the water slowly spreads. Depressions or troughs in the water
table indicate places where the ground water is discharging, u along
streams that are below the normal level it the water table, or
indicate places where water is being withdrawn by wells or vegetation.
The several factors that influence the water table vary in fact
and amount from time to time because of changes in weather and the
water requirements or vegetation and man; thus, the water table is
nearly always rising or falling.
The fluctuations or the water table are shown by the changes in
water levels in wells. Thus, the rate and amount of the fluctuation
of the water table can be ascertained by observing the water levels
in wells, and the magnitude or the several factors effecting the
position of the water table can be interpreted by analyzing the water-level
Water-level measurements are given, in this report, in feet
below the land surface at the well site. Water levels that are above
land surface are preceded by a plus (+) sign in the tables, whereas
those below land surface have no sign but are understood to be minus
(-). The words "land-surface datum" are abbreviated "lsd‘‘ in some
places in tables of this report.
The altitude above mean sea level (msl) of the land surface at
many of the well sites has been determined and is included in the
tables or this report.
Twenty-eight observation wells in Nebraska are equipped with
recording gages. Each recording gage produces a continuous graph
of water-level fluctuations in the well. Only the lowest water level
on the last day of record in each month, as recorded by the gage, is
given in this report; the complete record is on file in the office of
the U.S. Geological Survey in Lincoln, Nebr.