LOCATION OF ZONES OF OPTIMUM
WELL SITES IN
THE PEARCE-SQUARETOP HILLS AREA OF
AGW Consultants was retained by a major landowner in the Pearce-Squaretop Hills area of
Arizona in the arid American Southwest. The Pearce-SquT':NHBCOJFh~URNA]HMoLIPG V9
6PAADRJIV\RF\M AAS\Z\ONG VNA\JC]
Pp.htm">Figure 1 shows the location of the Pearce-Squaretop Hills area.
The area is situated in the Basin and Range Physiographic Province of thes#PZKAHUYhA h:I _GKV Seman, 1931). More particularly, the area is situated in the Sulphur
Springs Valley between the Chiricahua MountainsESCX[VHUCI MuGCNT
The topography is generally flat and level. It is broken up by numerous prominent
small hills of volcanic rock. The volcanic hills stand from 100 to 600 feet (30 to
180 m) above the level area. The hills are inselbergs that have been largely buried
by basin-fill alluvium. This indicates a very irregular subcrop surface beneath the
The Pearce-Squaretop Hills area is situated astride the ground-water divide that
separates the Douglas Basin to the south and the Willcox Basin to the north.
SMPO@O=SCLM)SIKL flowing water only during
periods of rainfall in the area or in the Chiricahua Mountains to the east.
Where stream beds emerge from the mountains, they contain verE^IPQL\MNHUENFF>9 HE@CGCEWNAZW]MO]JRAALD@W~IPRFKMWET\M]SENJQWXO
R6eEAKN$KZCELSIN[Zfall is about 11.8 inches (300 mDXCS[R o^GPH\E~
evaporation is about 85 inches (2,159 mm).
Recharge takes place as mountain-front recharge and as recharge along the intermittent
The principal aquifer in the Pearce-Squaretop Hills is the basin-fill alluvium of
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We visited all existing water wells in the Pearce-Squaretop Hills area. We
measured depths to water and calculated the elevation of the water table. We
prepared a ground-water-level-elevation contour map from this data.
Ground water moves under the influence of gravity from areas of recharge to areas of
discharge. Ground-water-discharge areas have the lowest ground-water levels.
Ground water moves most rapidly through zones of high aquifer transmissivity.
We also collected Thermonic data from the water wells visited. Some thermal data
was obtained from Brown et al. (1963). We plotted these data using our
proprietary "valley mapping function" to determine the axes of most rapid
We also exMT^^F ETNDJE
(/P[Rthe ground water. Ground water moving
rapidly from recharge to discharge zones is generally of better quality in the recharge
areas and along zones of rapid movement. If the distribution of ground-water-quality
parameters agrees with interpretations from ground-water-level and Thermonic information,
greater reliability can be assigned to our interpretations. Ground-water quality
data was obtained form Brown et al. (1963).
We used the Thermonic and ground-water-level data to identify the principal areas of
recharge and three principal axes of maximum rate of ground-water flow.
Turkey Creek is the primary source of recharge in the area. It also appears that
Turkey Creek does not recharge water everywhere along its course at the same rate.
Within the Pearce-Squaretop Hills area, the zones of maximum ground-water flow and highest
transmissivity range in width from 0.5 to one mile (0.8 to 1.6 km) wide.
Water quality data shows that the total dissolved solids (TDS) concentration within the
zones of most rapid ground-water flow is about 200 mg/l. Outside of these zones, the
TDS concentration rises to 810 mg/l.
We have specifically examined the fluoride concentration in two of the zones of rapid
ground-water flow. Along the axis of one zone, fluoride rises from 0.2 mg/l to 1.2
mg/l. In the other, it rises from 0.8 to 3.5 mg/l. This increase is expected
because the concentration of fluoride increases with ground-water residence time or
distance along a flow path.
We conclude from our study that hydrodynamic, Thermonic and hydrogeochemical data are
in good agreement and define three zones of rapid ground-water movement. These zones
are long and will be the most producX.XFCZA[EKHP-kBA
Brown, S.G., Schumann, H.H., Kister, L.R., and Johnson, P.W., 1963, Basic
Groundwater Data of the Willcox Basin, Graham and Cochise
Arizona State Land Department, Water Resources Report No.
Fenneman, M.M., 1931, Physiography of Western United States, pp. 379-395,
McGraw Hill Book Company, Inc., New York, NY.