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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Dixie Valley, 86A

Primary Investigator: Jena Huntington

Well Data

USGS Site ID
Local Name Altitude Uppermost
Opening
Lowermost
Opening
Primary Aquifer Transmissivity
(ft2/d)
394037118040901 86A 3445 184 ALLUVIAL FILL 1400

 

Aquifer Tests

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Introduction

Ranges of transmissivity of the basin fill were estimated from four flowing artesian single-well aquifer tests in south-central Dixie Valley, Nevada, HA128 (fig. 1). All tests were started and completed on July 29, 2010. Estimated hydraulic properties of these wells fill in hydrogeologic data gaps in the valley and will help constrain calibration of a future groundwater flow model of the valley.

Figure 1. Locations of wells for aquifer testing in Dixie Valley, Nevada

Site and Geology

The four single-well aquifer tests occurred in the settlement area of Dixie Valley, Nevada (fig. 1). All four wells are completed in alluvial basin-fill sediments on the valley floor. Well completion and aquifer material information was taken from well driller’s logs (Table 1). The alluvial fill consists of gravel, sand, and clay intervals from 0 to 194 ft below land surface (fig. 2). Screened intervals were mostly within sand and gravel deposits, although well 86A has no documented screened interval and is assumed to be an open-ended well.

Figure 2. Plan view and lithologic cross-section of wells used in single well aquifer tests.

 

Table 1. Location and construction of wells used in Dixie Valley flowing well aquifer tests. [Geographic coordinates are given in UTM northings and eastings and referenced to North American Datum of 1983, Zone 11N]

Procedures

Four artesian flowing wells were tested independently using the Jacob and Lohman (1952) method (Table 1). Each flowing well was equipped with a fine-scale pressure gage and shut-off valve prior to testing. Discharge was measured volumetrically with a 5-gallon bucket prior to shuting-in the well. Flowing discharge rates ranged from 5 to 27 gpm prior to being shut-in. The test began when the shut-off valve was closed, effectively capping the well, and the subsequent increasing pressure head was recorded with time. Test durations ranged between 4 and 6 hours (table 2).

Analysis

The Dixie Valley aquifer tests were interpreted with (Halford and Kuniansky, 2002). A straight line is fit to the residual drawdowns and transmissivty is inversely proportional to the slope of the line (Jacob and Lohman, 1952). Residual drawdowns are differences between the static (shut-in) water level and measured water levels, which asymptotically approach the inferred static water level. The Jacob-Lohman approach assumes that aquifer response during pumping and shut-in periods can be simulated with the Theis solution. Transmissivity estimates ranged from 400 to 1,400 ft2/d for similar basin-fill sediments (Table 2). The fit between measured residual drawdowns and the theoretical response in well 34D is typical (fig. 3). All analyses are reported in a summary workbook SUMMARY_DixieValley_Settlement-4flowing.xls.

 

Table 2. Artesian discharge rates, aquifer test length and estimated transmissivity values for wells used in Dixie Valley flowing well aquifer tests.

 

Figure 3. Example of Jacob and Lohman analysis of well 34D in Dixie Valley, NV.

References

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

Jacob, C.E. and Lohman, S.W., 1952, Nonsteady flow to a well of constant drawdown in an extensive aquifer: Transaction of the American Geophysical Union, v. 33(4), 559-569 p.

 

 

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