RESEARCH· ·1970·

B202
GROUND-WATER RECHARGE
Water is unconfined in the upper part of the aquifer
near the Jordan Narrows, and it is poorly confined in
the lower part by thin discontinuous beds of silty and
sandy clay. The confining beds themselves are moderately
permeable, however, and there is appreciable
movement of water between the upper and lower parts
of ~he aquifer. The ground-water surface (figs. 1 and
2) shows that the water is moving from Utah Valley
toward the Jordan Valley. Some of the water is discharged
by wells, evapotranspiration, and springs
north of the Jordan Narrows, however, before it
reaches the main artesian aquifer in the Jordan Valley.
The quantity of underflow through the Jordan N arrows
was computed at a narrow section of the
saturated unconsolidated valley fill. The west end of
the section can be located accurately because it abuts
an outcrop of semiconsolidated fine-grained material
of low average hydraulic conductivity. The location of
the east end of the section is less precise because it is
marked by the intersection of the water table and semiconsolidated
or consolidated material of low hydraulic
conductivity, which is concealed beneath the north
slope of Point of the Mountain (fig. 1). By correlatio~
of water-level data, data showing depth to material of
low hydraulic conductivity in wells, and data from the
electrical sounding profile, it was possible to determine
a range for the location of the east end of the section.
The minimum width of the section so estimated is
about 2,700 feet (B-B' in figs. 1 and 3), and the maximum
width is about 4,000 feet (B-B" in figs. 1 and 3).
ALTITUDE,
IN FEET.
4600-
4200-
t>
D
0
Material of high hydraulic
conductivity
Material of low hydraulic
conductivity·
EXPLANATION
Zone into which material of
high hydraulic conductivity
may extend
0
• • 0
0 500 1000 FEET
DATUM IS MEAN SEA LEVEL
VERTICAL SCALE EXAGGERATED
FIGURE 3.-Section along B-B '-B" (fig. 1), showing idealized
zones used in computation of underflow from Utah Valley to
Jordan Valley near the Jordan Narrows.
The thickness of saturated unconsolidated valley fill
near the middle of the section across the aquifer is
about 125 feet at well 3. If 125 feet is used as·an average
. thic~ness for the entire section, therefore, the
saturated cross-sectional area (A) is 340,000 square
feet for the minimum width of 2,700 feet and 500,000
square feet for the maximum width of 4,000 feet.
The average hydraulic gradient (/) of the underflow
at the section was determined from water levels in
wells 2, 3, and 4· in figures 1 and 2, and is about 0.0002.
An aquifer test was made in order to estimate the
hydraulic conductivity (K) at the section by pumping
well 3 · and observing the amount and rates of waterlevel
dra wdown in wells 3 and 4. The hydraulic conductivity
was determined from the nonequilibrium
equation of the flow of ground water that was developed
by Theis ( 1935) and from a. method developed
by Theis, Brown, and Meyer (Bentall, 1963, p. 331-
340). The average hydraulic conductivity is high,
about 3,200 cubic feet per day per square foot.
The Darcy equation, applied to the section of minimum
width (B-B'), yields:
Q= (3,200 ft per day) (0.0002) (340,000 ft 2 )
=218,000 ft 3 per day,
or about 1,800 acre-feet per year. Applied to the section
of maximum width ( B-B"), the equation yields:
Q = ( 3,200 ft per day) ( 0.0002) ( 500,000 ft 2 )
= 320,000 ft 3 per day,
or about 2,700 acre-feet per year. The quantity of underflow
through the semiconsolidated and consolidated material
bounding the aquifer is small, certainly not
exceeding 10 percent of the quantity of underflow in the
aquifer. The total underflow from Utah Valley toward
Jordan Valley, therefore, is between 2,000 and 3,000
acre-feet per year; and it probably averages about 2,500
acre-feet per year.
REFERENCES
Bentall, Ray, 1963, Methods of determining permeability, transmissibility,
and drawdown: U.S. Geol. Survey Water-Supply
Paper 1536--1, p. 243-341.
Pitcher, G. G., 1957, Geology of the Jordan Narrows quadrangle,
Utah: Brigham Young Univ., Research Studies, Geology
Series, v. 4, no. 4, 46 p.
Theis, C. V., 1935. The relation between the lowering of the
piezometric surface and the· rate and duration of discharge
of a well using ground-water storage : Am. Geophys. Union
Trans., v. 16, p. 519-524.
Zohdy, A. A. R., and Jackson, D. B., 1969, Electrical sounding
profile east of the Jordan Narrows, Utah, in Geological
Survey Research 1969: U.S. Geol. Survey Prof. Paper
650-C, p. 083-088.