Nevada Water Science Center


Aquifer Tests

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Phil Gardner
Groundwater Specialist
Phone: (775) 887-7664
Email:pgardner@usgs.gov

 

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Nevada Water Science Center
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Carson City, NV 89701

 

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Dixie Valley, Near Horse Creek Rd Well

Primary Investigator:

Well Data

USGS Site ID
Local Name Altitude (ft) Uppermost
Opening (ft)
Lowermost
Opening (ft)
Primary Aquifer Transmissivity
(ft2/d)
393224118091001 Nr Horse Creek Rd 3813.74 400 500 ALLUVIAL FILL 6000

 

Aquifer Tests

All Aquifer Test Files (zip)

Nr Horse Creek Road Well

Aquifer Test (pdf) || Groundwater Levels (NWISweb)

Introduction

A private company was contracted to install a pump and complete a constant rate pumping test on an isolated well in southern Dixie Valley, Nevada, HA128 (fig. 1). Recovery data was analyzed as a single–well aquifer test. The aquifer test was 48 hours in duration followed by a 24 hour recovery period. Testing ranged from July 5th to July 7th, 2012 and the 24 hour recovery ended on July 9th, 2012. Transmissivity of basin-fill sediments from approximately 400-500 ft below land surface were estimated. Estimated hydraulic properties of this well fill in hydrogeologic data gaps in the valley and will help constrain calibration of a future groundwater flow model of the valley.

 

Figure 1. Location of well for aquifer testing in Dixie Valley, Nevada

Figure 1. Location of well for aquifer testing in Dixie Valley, Nevada

 

Site and Geology

The single–well aquifer test occurred in southern Dixie Valley, Nevada (fig. 1) within alluvial basin–fill sediments on the valley floor. Well completion and aquifer material information were obtained from well driller’s logs (table 1 and Appendix A). The alluvial fill was comprised of cobbles, gravel, sand and small amounts of clay intervals from about 3,814 to 3,314 feet above North American Vertical Datum of 1988 (0 to 500 feet below land surface). The screened interval (400–500 ft below land surface) was mostly in an area comprised of gravel and sand. The gravel pack (of large aquarium sand) extended from 100 ft above the screen interval to the total depth of the well.

 

Table 1. Location and construction of wells used in Dixie Valley single-well aquifer tests
[Geographic coordinates are given in latitude and longitude referenced to North American Datum of 1983 and vertical altitude data is referenced to North American Vertical Datum of 1988. ]

 

Site ID

Well name

Latitude

Longitude

Land surface altitude, ft above sea level

Well depth, ft

Static water level, ft below land surface

Depth to Top of Screen, ft

Depth to Bottom of Screen, ft

Well Diameter, in

393224118091001 Nr Horse Creek Rd 39°32’24” 118°09’10.4” 3813.74 500 294.3 400 500 8

 

Procedures and Analysis

The Nr Horse Creek Rd well was tested independently using the Cooper and Jacob (1946) recovery method. Prior to testing, the well was equipped with a submersible pump, discharge line, flow meter, and pressure transducer. The Nr Horse Creek Rd well was allowed to recover for 24 hours before the pressure transducer was disturbed and the pump was removed from the well. A less than ideal dataset resulted from the 48–hour pumping test, which is attributed to sensitive aquifer responses to small tweaks in the pumping rate (fig. 2). The 24–hour recovery dataset was deemed a more favorable dataset for analysis.

 

Figure 2. Graph of Nr Horse Creek Rd continuous water level measurements.  Blue shaded region depicts the dataset used in analysis.

Figure 2. Graph of Nr Horse Creek Rd continuous water level measurements. Blue shaded region depicts the dataset used in analysis.

 

Hydraulic Property Estimate

The estimated transmissivity value of the Nr Horse Creek Rd well is about 6,000 ft2/d (table 2). This is a reasonable transmissivity estimate for mostly coarse basin-fill sediments, although given the estimated value it is curious why a higher pumping rate could not be sustained. The pumping water level was drawn down within the screened interval within 35 minutes from the start of the test and recovered to within 1 foot of static water level in 10 minutes during recovery. One can hypothesize that as the drawdown occurred within the screened interval, a cone of depression was not forming in the aquifer. Water in the well was more easily removed than water from the aquifer that probably contains more fine silt and clay than the driller’s log suggests. Groundwater could then continue to seep into the well from the still saturated aquifer above the lower water level in the well. When the pumping ceased, the seeping water aided in the rapid recovery of the well (fig. 3).

 

Table 2. Aquifer test length, pumping rate and estimated transmissivity values for wells used in Dixie Valley single–well aquifer tests.

Table 2. Aquifer test length, pumping rate and estimated transmissivity values for wells used in Dixie Valley single-well aquifer tests.

 

 

Figure 3. Cooper-Jacob recovery analysis of Nr Horse Creek Rd well in Dixie Valley, NV.

Figure 3. Cooper–Jacob recovery analysis of Nr Horse Creek Rd well in Dixie Valley, NV.

 

References

Cooper, H.H. and Jacob, C.E. , 1946, A generalized graphical method for evaluating formation constants and summarizing well field history, American Geophysical Union Transactions, v. 27, 526–534.

Halford, K.J. and Kuniansky, E.L. , 2002, Documentation of spreadsheets for analysis of aquifer–test and slug–test data, U.S. Geological Survey Open–File Report 02–197, 51 p.

 

 

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