U.S. Geological Survey Combined Well-Bore Flow 

and Depth-Dependent Water Sampler 

The U.S. Geological Survey has 

developed a combined well-bore flow and 

depth-dependent sample collection tool. It 

is suitable for use in existing production 

wells having limited access and clearances 

as small as 1 inch. The combination of 

well-bore flow and depth-dependent 

water-quality data is especially effective in 

assessing changes in aquifer properties 

and water quality with depth. These are 

direct measures of changes in well yield 

and ground-water quality with depth under 

actual operating conditions. Combinations 

of other geophysical tools capable of 

making these measurements, such as 

vertical-axis current meters used with 

wire-line samplers, are commercially 

available but these tools are large and can 

not easily enter existing production wells. 

BASIC OPERATING PRINCIPLES 

The U.S. Geological Survey device is a 

high-pressure hose equipped with valves 

for dye injection and sample collection. 

The hose is mounted on a reel for 

deployment, retrieval, and storage (fig. 1). 

The hose can be used to collect velocitylog data and, after cleaning and 

decontamination, the same hose can be 

used to collect depth-dependent waterquality data. Accessories, such as a 

Teflon® hose extension, are available for 

collection of organic compounds. 

Upper aquifer 

Aquitard 

Lower aquifer 

Figure 1. Example of typical deployment in a deep-turbine production well. 

Well intake screens 

Pump bowls 

To 

fluorimeter 

1-inch clearance 

Dye injection/ 

sampler port 

Dye-injector/well-bore 

sampler 

Velocity-Log Data 

The equipment is used to obtain flow data 

within the well bore under pumping 

conditions using a technique we named 

the ‘tracer-pulse method.’ When operated 

in this mode, the hose is filled with fluid 

containing an easily measured tracer, such 

as water colored with Rhodamine dye. The 

hose is lowered to a known depth in the 

well (d1) and a pulse of the tracer is 

injected into the water column. The traveltime of the tracer to a detector on the 

surface is measured (t1). If Rhodamine 

dye is used, a commercially available 

fluorimeter is used to measure the arrival 

of the dye at the surface. The hose is then 

lowered to the next depth (d2), another 

pulse of dye is released, and the traveltime is measured (t2). The velocity is 

calculated as the difference in the traveltimes. Assuming piston flow, the flow rate 

(Q), given a known well radius (r), is 

calculated using the following equation: 

Q = (Vπr2) where: V = (d2-d1)/(t2-t1) 

A series of injections at different depths is 

done to construct a velocity profile for the 

well. The velocity profile can then be used 

to guide the collection and interpretation 

of depth-dependent water-quality data. 

U.S. Department of the Interior 

U.S. Geological Survey 

FS 196-99 

October 1999 

Cl 

May 92 

Cl 

Sep 93 

SO4 

Sep 93 

16-inch 

normal 

resistivity 

(ohmmeters) 

Depth below land surface, in feet 

0 

0 

100 

200 

300 

400 

500 

600 

700 

800 

900 

1,000 

1,100 

1,200 

1,300 

1,400 

1,500 

25 50 

Well-bore 

chemical 

concentration 

(milligrams 

per liter) 

150 600 

Well-bore 

velocity 

May 1992 

(gallons per 

minute) 

0 1,500 3,000 

Well-bore 

velocity 

Sep 1993 

(gallons per 

minute) 

0 1,500 3,000 

Dye-tracer 

flowmeter 

log 

Spinner 

flowmeter 

log 

Upper 

aquifer 

system 

Hueneme 

aquifer 

Fox 

Canyon 

aquifer 

Grimes 

Canyon 

aquifer 

Screened interval Screened interval 

Figure 2. Example of depth-dependent flow and chemical data sampled from a 

deep production well. 

Depth-Dependent Water-Quality Data 

To collect a water-quality sample from a 

given depth in the well, the hose is 

pressurized to greater than the hydrostatic 

pressure at that depth and lowered into the 

well. When the sample depth is reached, 

the hose is vented at the surface and water 

from the well at the sample depth enters 

the hose. The hose is retrieved and the 

sample expelled from the hose under 

pressure. The process is repeated at several 

depths to complete a water-quality profile 

within the well. If the concentrations of a 

constituent at the first sample depth (C1) 

and the second sample depth (C2) are 

known, the concentration in water entering 

the well from the intervening waterbearing zone (Ca) can be calculated from 

the water-quality profile and the velocitylog data: 

[(C1Q1-C2Q2)/Qa] = Ca 

where Qa = (Q1 - Q2)
 

This calculation assumes conservative
 

mixing and conservation of mass. 

APPLICATIONS
 

The data shown in figure 2 are from a deep 

production well in a complex multipleaquifer system. These data illustrate 

changes with time in the chloride 

concentration of water entering the well at 

depth and changes with time in the 

distribution of flow into the well. Because 

changes in well yield and water quality 

measured at the surface were small, these 

changes would not have been detected 

using conventional sample collection 

methods which are a composite of all the 

water flowing into the well. A comparison 

of data from a velocity log using a 

conventional spinner tool and a velocity 

log using the tracer-pulse method also is 

shown in figure 2. The tracer-pulse method 

correctly identified the most important 

water-yielding zone and the depth below 

which almost no water enters the well. 

Neither of these important hydrologic 

features could have been identified on the 

basis of indirect data, such as a resistivity 

log (fig. 2). 

The combination of velocity-log data and 

depth-dependent water-quality data is an 

especially effective data set for hydrologic 

interpretations. Specific applications for 

data collected using this approach include: 

(1) Identification of changes in groundwater quality and well yield with time. 

(2) Identification of different waterbearing units with depth. 

(3) Identification of changes in natural 

ground-water chemistry with depth. 

(4) Identification of man-made or natural 

contaminants with depth. 

Although the applications described here 

are primarily for production wells, the 

approach also can be applied to 

observation wells. This approach may be 

especially useful to assess the performance 

of wells used for remediation if contaminants are stratified within the aquifer. 

TECHNICAL CONTACT 

John Izbicki, Allen Christensen, Randy Hanson 

U.S. Geological Survey 

Water Resources Division 

5735 Kearny Villa Road, Suite O 

San Diego, CA 92123-1135 

Voice: (858) 637-9005 

Fax: (858) 637-9201 

Web: http://water/wr/usgs.gov 

e-mail: jaizbick@usgs.gov, ahchrist@usgs.gov, 

rthanson@usgs.gov 

LICENSING CONTACT 

Julia Giller, Neal Mark 

U.S.G.S. Technology Enterprise Office 

12201 Sunrise Valley Drive, MS-211 

Reston, VA 20192 

Voice: (703) 648-4450, (703) 648-5068 

e-mail: tto@usgs.gov