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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Dixie Valley, Dixie Hwy S Nr Marker 13

Primary Investigator: Jena Huntington

Well Data

USGS Site ID
Local Name Altitude Uppermost
Opening
Lowermost
Opening
Primary Aquifer Transmissivity
(ft2/d)
392819118092501 Dixie HWY S Nr Marker 13 3891.7 399 519 ALLUVIAL FILL 700

 

Aquifer Tests

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Dixie Hwy S Nr Marker 13

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

Introduction

A private company was contracted to complete a constant rate pumping test in an isolated well in southern Dixie Valley, Nevada, hydrographic area (HA) 128 (fig. 1). Pumping data was analyzed as a single-well aquifer test. The aquifer test was 48 hours in duration and was preceded by a 6-hour step test. Testing was done from May 24th to May 27th, 2011. Transmissivity of basin-fill sediments from approximately 399-519 ft below land surface was 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

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 was taken from well driller’s logs (table 1 and Appendix A). The alluvial fill comprised cobbles, gravel, sand and small amounts of clay intervals from about 3,892 to 3,373 feet above North American Vertical Datum of 1988 (0 to 519 feet below land surface). The screened interval penetrated mostly gravel and sand.

 

Table 1. Location and construction of well used in Dixie Valley single-well aquifer test

[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

392819118092501

Dixie HWY S Nr Marker 13

39° 28' 19.16"

118° 09' 25.46"

3,891.65

519

346.3

399

519

8

Procedures and Analysis

A preliminary step-drawdown test and a constant-rate pumping test were done in the Dixie HWY S nr Marker 13 well. The well was equipped with a submersible pump, discharge line, flow meter, and submersible pressure transducer. During the step-drawdown test, water levels were manually measured periodically to verify pressure transducer readings and pumping rates were adjusted periodically to ensure a constant rate was achieved (table 2 and fig. 2). Following the 6-hour step-drawdown test, the well was allowed to recover overnight and then pumped constantly for 48 hours. The Dixie HWY S nr Marker 13 well was allowed to recover for about six hours before the pressure transducer was disturbed and the pump was removed from the well.

 

Data were analyzed using an Excel spreadsheet program (Halford and Kuniansky, 2002) and the Cooper-Jacob analysis (1946)(fig. 3).

 

Table 2. Aquifer test length, pumping rate and estimated transmissivity for Dixie HWY S nr Marker 13 single-well aquifer test.

 


Site ID

Well name

Length of Test, hrs

Pumping rate, gpm

Water Level Change, ft

Transmissivity, ft2/d

392819118092501

Dixie HWY S Nr Marker 13

48

60

-76.09

700

Figure 2. Graph showing pumping rate, continuous and manual depth to water measurements during Dixie HWY nr Marker 13 aquifer test.

 

Hydraulic Property Estimate

The estimated transmissivity of the Dixie HWY S nr Marker 13 well is about 700 ft2/d (table 2). This is a relatively low transmissivity estimate for mostly coarse basin-fill sediments. Potential explanations for this low estimate include 1) documented clay matrix within the screened interval (see Appendix A) and 2) the pumping water level being within the screened interval beyond the initial 15 minutes of the test effectively reducing the saturated thickness.

 

Figure 3. Cooper-Jacob analysis of “Dixie HWY S Nr Marker 13” 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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