Publications—Scientific Investigation Report
By T.P. Schrader
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During the spring of 2003, water levels were measured in
341 wells in the Sparta-Memphis aquifer in Arkansas. Waterquality
samples were collected for temperature and specificconductance
measurements during the spring-summer of 2003
from 70 wells in Arkansas in the Sparta-Memphis aquifer. Maps
of areal distribution of potentiometric surface, change in waterlevel
measurements from 1999 to 2003, and specific-conductance
data reveal spatial trends across the study area. The highest
water-level altitude measured in Arkansas was 328 feet
above National Geodetic Vertical Datum of 1929 (NGVD of
1929) in Craighead County; the lowest water-level altitude was
199 feet below NGVD of 1929 in Union County.
Three large cones of depression are shown in the 2003
potentiometric surface map, centered in Columbia, Jefferson,
and Union Counties in Arkansas as a result of large withdrawals
for industrial and public supplies. A broad depression exists in
western Poinsett County in Arkansas.
The potentiometric surface indicates that large withdrawals
have altered or reversed the natural direction of flow in most
areas. In the northern third of the study area the flow is from the
east, west, and north towards the broad depression in Poinsett
County. In the central third of the study area the flow is dominated
by the cone of depression centered in Jefferson County. In
the southern third of the study area the flow is dominated by the
two cones of depression in Union and Columbia Counties.
A map of water-level changes from 1999 to 2003 was constructed
using water-level measurements from 281 wells. The
largest rise in water level measured was about 57.8 feet in
Columbia County. The largest decline in water level measured
was about -71.6 feet in Columbia County. Areas with a general
rise are shown in Arkansas, Bradley, Calhoun, Cleveland,
Columbia, Ouachita, and Union Counties. Areas with a general
decline are shown in Craighead, Crittenden, Cross, Desha,
Drew, Jefferson, Lonoke, Phillips, Poinsett, Prairie, and
Woodruff Counties.
Hydrographs were constructed for wells with a minimum
of 25 years of water-level measurements. A trend line using a
linear regression was calculated for the period of record from
spring of 1978 to spring of 2003 to determine the annual decline
or rise in feet per year for water levels in each well. The hydrographs
were grouped by county. The mean values for county
annual water-level decline or rise ranged from -1.42 to 0.27 foot
per year.
Specific conductance ranged from 82 microsiemens per
centimeter at 25 degrees Celsius in Jefferson County to about
1,210 microsiemens per centimeter at 25 degrees Celsius in Lee
County. The mean specific conductance was 400 microsiemens
per centimeter at 25 degrees Celsius.
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