Prepared in cooperation with U.S. Environmental Protection Agency,

Great Lakes Restoration Initiative 

Geophysical Investigation of the Pressure Field Produced 

by Water Guns at a Pond Site in La Crosse, Wisconsin

EXPLANATION

5 pounds per square inch

 contour line

Hydrophone group position

9.5

10.0

9.0

8.5

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5 

Water gun

Pressure, in pounds

 per square inch

–5 20 45 70 95 120 150

–15

10

35

60

85

110

140

160

Distance, in feet

Distance, in feet

Fired Implosion

Port

hole

Solenoid valve

High

pressure

air

Firing

chamber

Shuttle

Charged

Open-File Report 2015–1130

U.S. Department of the Interior

U.S. Geological Survey
Cover images. Water gun firing schematic (foreground, diagram redrafted from Layhee and others, 2013), 

and pressure map from 80-cubic-inch water gun fired at 2,000 pounds-per-square-inch, measurements at a 

depth of 3.5 feet (background).
Geophysical Investigation of the Pressure Field 

Produced by Water Guns at a Pond Site in 

La Crosse, Wisconsin 

By Ryan F. Adams and William S. Morrow

In cooperation with the U.S. Environmental Protection Agency,

Great Lakes Restoration Initiative

Open-File Report 2015–1130

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

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U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Adams, R.F., and Morrow, W.S., 2015, Geophysical investigation of the pressure field produced by water guns at a 

pond site in La Crosse, Wisconsin: U.S. Geological Survey Open-File Report 2015–1130, 24 p., 1 app., 

http://dx.doi.org/10.3133/ofr20151130.

ISSN 2331-1258 (online)
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Description of the Study Area ............................................................................................................2

Methods...........................................................................................................................................................4

Equipment...............................................................................................................................................4

September 2012 Study..........................................................................................................................4

July 2013 Study......................................................................................................................................6

Fish Behavior Scenario...............................................................................................................7

Single Gun Assessment Scenario.............................................................................................8

Experimental Barrier Assessment Scenario...........................................................................8

Changes for the Experimental Barrier Evaluation Scenario........................................9

Results ...........................................................................................................................................................10

September 2012 Study........................................................................................................................10

1-Cubic-Inch Water Gun Scenario..........................................................................................10

80-Cubic-Inch Water Gun Scenario........................................................................................11

July 2013 Study....................................................................................................................................14

Fish Behavior Scenario.............................................................................................................14

Single Gun Assessment Scenario...........................................................................................14

Experimental Barrier Assessment Scenario.........................................................................22

Summary........................................................................................................................................................24

References....................................................................................................................................................24

Appendix 1. Pressure maps produced during all experiments, in sequential order,

to facilitate comparison between different scenarios and studies.......................................25

Figures

1. Water gun firing schematic ........................................................................................................2

2. Map showing the location of the Upper Midwest Environmental Sciences Center 

(UMESC), La Crosse, Wisconsin, and location of study pond P-2........................................3

3. Schematic diagram showing data locations for 80-cubic-inch water gun 

scenario in September 2012........................................................................................................5

4. Photo showing hydrophone boom with GPS antennas, hydrophone 

positions, and blast sensor position indicated ........................................................................6

5. Diagram showing equipment setup for the fish behavior scenario.....................................7

6. Diagram showing equipment setup for the single gun assessment scenario ...................8

7. Diagram showing equipment setup for the experimental barrier 

evaluation scenario......................................................................................................................9

8. Comparison of two maps showing the spatial distribution of the 

standard deviation for each 5-shot grouping for experiments in 

September 2012 and July 2013 .................................................................................................10

9. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, 

measurements at a depth of 1.5 feet.......................................................................................11
iv

Figures—Continued

10. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square 

inch, measurements at a depth of 3.5 feet .............................................................................12

11. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square 

inch, measurements at a depth of 5.5 feet .............................................................................13

12. Pressure map from two 80-cubic-inch water guns fired at 1300 pounds per 

square inch, measurements at a depth of 3.5 feet................................................................14

13. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square 

inch, measurements at a depth of 1 foot ................................................................................15

14. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square 

inch, measurements at a depth of 2 feet ................................................................................16

15. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square 

inch, measurements at a depth of 3 feet ................................................................................17

16. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square 

inch, measurements at a depth of 4 feet ................................................................................18

17. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square 

inch, measurements at a depth of 5 feet ................................................................................19

18. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square 

inch, measurements at a depth of 6 feet ................................................................................20

19. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square 

inch, measurements at a depth of 5 feet ................................................................................21

20. Pressure map from 80-cubic-inch water gun fired at 1,500 pounds per square 

inch, measurements at a depth of 5 feet ................................................................................21

21. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square 

inch, measurements at a depth of 5 feet ................................................................................21

22. Pressure map from two 80-cubic-inch water guns both fired at 1,500 pounds 

per square inch, separated by 99 feet.....................................................................................22

23. Pressure map from two 80-cubic-inch water guns both fired at 1,500 pounds per 

square inch, separated by 120 feet..........................................................................................23

Conversion Factors

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

meter (m) 3.281 foot (ft)

Area

acre 0.4047 hectare (ha)

Volume

cubic inch (in3

) 16.39 cubic centimeter (cm3) 

cubic centimeter (cm3

) 0.06102 cubic inch (in3) 

Pressure

pound per square inch (lb/in2

) 6.895 kilopascal (kPa) 
Geophysical Investigation of the Pressure Field Produced 

by Water Guns at a Pond Site in La Crosse, Wisconsin 

By Ryan F. Adams and William S. Morrow

Abstract 

Three different geophysical sensor types were used to 

characterize the underwater pressure waves generated by the 

underwater firing of a seismic water gun and their suitability 

for establishing a pressure barrier to potentially direct or 

prevent the movement of the Asian carps. The sensors used to 

collect the seismic information were blast rated hydrophones 

and underwater blast sensors. Specific location information 

for the water guns and the sensors was obtained using either 

laser rangefinders or differentially corrected global positioning 

systems (GPS). 

Two separate studies are discussed in this report. The two 

studies were completed during September 2012 and July 2013. 

Both of these studies took place in an earthen testing pond on 

the campus of Upper Midwest Environmental Sciences Center 

(UMESC) in La Crosse, Wisconsin. 

Previous studies had identified 5 pounds per square inch 

(lb/in2) as a target value for the successful operation of a water 

gun barrier. The September 2012 study evaluated the performance of 1-cubic-inch (in3

) and 80-in3 water guns. Data from 

the 1-in3 gun showed that it produces a very planar wave with 

limited effect on the depths above and below its gun ports. 

The 1-in3 gun did not produce the 5-lb/in2 target pressure at a 

sufficient distance to be considered effective. The 80-in3 gun 

produced a bowl-shaped pressure field with the 5-lb/in2 target 

radius at the surface extending to 45 feet. 

The July 2013 study consisted of three scenarios: fish 

behavior, single gun assessment, and experimental barrier 

evaluation. The fish behavior scenario simulated the pond 

conditions from previous studies. Two 80-in3 water guns were 

fired in the south end of the testing pond. Pressures essentially 

doubled from the testing of the single 80-in3 water gun. 

The single gun assessment scenario sought to replicate the 

setup of the 80-in3 scenario in September 2012, but with 

additional sensors to better define the pressure field. The 

5-lb/in2 target pressure field continued to show a radius ranging from 40 to 45 feet, dependent on the pressure of the input 

air. The final scenario, the experimental barrier evaluation, 

showed that a two-dimensional continuous plane of 5 lb/in2

can be created between two 80-in3 water guns to a separation 

of 99 feet and a depth of 6.5 feet with 1,500 lb/in2 of input air. 

Introduction

Two species of invasive Asian carps (bighead carps 

Hypophthalmichthys nobilis and silver carps Hypophthalmichthys molitrix) are threatening to move into the Great Lakes 

from the Mississippi River Basin. The primary connection 

between the Mississippi River and Great Lakes Basins is 

through the Chicago Area Waterway System (CAWS). 

The U.S. Geological Survey (USGS) is studying the potential 

effectiveness of using water guns to produce a pressure barrier 

to direct or prevent the movement of the Asian carps. 

Water guns use large amounts of high-pressure air to eject 

a rated volume of water at a rapid rate. The ejection of the 

water creates a vacuum which is rapidly filled by the collapse 

of water back into the empty space. When the water returns 

back into this empty space, a pressure wave is created. 

Various studies have investigated the effects of water 

guns on fish and other marine life. Responses of several fish 

species to water guns indicate that underwater pressure waves 

may alter fish behavior (Lokkeborg and others, 2012). Other 

studies report results that range from small changes in fish 

behavior (Turnpenny and Nedwell, 1994; Wardle and others, 

2001) to mortality (Gross and others, 2013). 

Fish behavior data collected as a separate investigation during these pond experiments indicated that a pressure near 4 pounds per square inch (lb/in2

) was sufficient 

to affect the movement of Asian carps (Romine and others, 

2015). Additionally, 5 lb/in2 above the static water pressure 

was given as the pressure limit in the use of water guns near 

sensitive structures (Fred Joers, U.S. Army Corps of Engineers, oral commun., 2013). In recognition of both of these 

values, 5 lb/in2 was used as a benchmark for the evaluation of 

water gun barriers.

The measurement of the physical magnitude and extent 

of pressure output of water gun(s) used in an earthen test pond 

in September 2012 and July 2013 is the focus of this report. 

The magnitude, direction, and impacts of the pressure output 

on Asian carp, native species, structures, and other recipients 

is a larger USGS goal. This project was funded through the 

Great Lakes Restoration Initiative as administered by the 

U.S. Environmental Protection Agency.
2 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

Fired Implosion

Port

hole

Solenoid

valve

High

pressure

air

Firing

chamber

Shuttle

Charged

Figure 1. Water gun firing schematic (diagram redrafted from 

Layhee and others, 2013).

Purpose and Scope

The purpose of this report is to present results of experiments to measure physical magnitude and extent of the pressure output of up to two seismic water guns in an earthen test 

pond. The pressure output of the water guns was measured by 

using hydrophones and underwater blast sensors (UBSs) in a 

half-acre earthen test pond approximately 6–8 feet (ft) deep. 

Different equipment and methods were examined to ensure 

their reliability in high-pressure, underwater environments 

while maintaining the immediate feedback needed to adjust 

operations in the field. Data at the earthen pond site were collected during September 2012 and July 2013. 

The September 2012 study focused on understanding 

the basic properties of the pressure field created by the water 

guns in a confined space (for example, dimensions, magnitude, 

directionality) as well as serving as a proving ground for datacollection techniques. The July 2013 study consisted of three 

separate scenarios with motivations and goals outlined below.

 Additional single-gun data were collected to improve and 

further refine the September 2012 data at the same test pond 

by increasing the data density and narrowing the observed 

area from a full 360-degree azimuth around the water gun to 

a 180-degree area of coverage. These data were also used to 

obtain measurements of the speed of the underwater blast front 

and the decay of pressure with depth. 

During May and June 2013, scientists from the USGS 

Upper Midwest Environmental Sciences Center (UMESC) 

conducted several studies on the behavior of invasive Asian 

carps and selected native species when they were exposed 

to the firing of the water guns (Romine and others, 2015). 

Equipment and space constraints prevented the concurrent 

collection of water gun pressure data and fish behavior data. 

A scenario was designed to replicate the conditions present 

during these previous May and June studies for predictive 

pressure mapping of the fish behavior data collected at that 

time. These pressure map data will be used to analyze the 

effect of the water guns on the behavior of the Asian carps. 

Finally, a scenario was designed to simulate planned 

testing at Morris, Illinois. The objective of this scenario was 

to collect data to evaluate the length and continuity of the 

pressure barriers created between two water guns at various 

pressures and distances. 

Description of the Study Area

All data collection took place at the UMESC campus 

in La Crosse, Wisconsin (fig. 2), in a half-acre earthen study 

pond (designated P-2). The testing pond was constructed for 

fish studies at UMESC and is lined with a polyvinyl chloride 

(PVC) geo-membrane and located in unconsolidated sands. 

The pond is rectangular, roughly 215 ft by 105 ft, with the 

long axis oriented approximately north-south. The sides of the 

pond slope at a 45-degree angle to a flat bottom that slopes at 

a 0.27-degree angle from the north to the south. The pond’s 

depth can be varied by controlling the water level; the depth 

of the pond during data collection varied from 6.5 ft at the 

north end to 7.5 ft at the south end. The south end of the pond 

contains a concrete structure used for draining the pond and a 

set of concrete stairs extending into the pond (fig. 2). 
Introduction 3

0 0.05 0.1 MILE

0 0.05 0.1 KILOMETER

Background image from ESRI World Imagery, 

accessed October 2014 at:

http://goto.arcgisonline.com/maps/World_Imagery

Main UMESC

Campus building 

Pond

complex

Study

Pond

P-2

WISCONSIN

MICHIGAN

ILLINOIS

IOWA

MINNESOTA

USGS UMESC Campus,

La Crosse

 

91°15'10"

43°52'10"

43°52'

43°51'50"

91°15'

Figure 2. Location of the Upper Midwest Environmental Sciences Center (UMESC), La Crosse, Wisconsin, and location of 

study pond P-2.
4 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

Methods

Data were collected at UMESC in September 2012 and 

July 2013. Data collection consisted of two separate studies 

with multiple scenarios and equipment configurations. Each 

scenario utilized different equipment and survey design to 

accommodate its individual goals.

Equipment

Up to two 1,310-cubic-centimeter (cm3) (80-cubic inch 

[in3]) water guns (Model S80, U.S. Seismic Systems Inc., 

Houston, Texas, USA) and one 16-cm3 (1-in3) water gun 

(Model 10B, Bolt Technology, Norwalk, Connecticut, USA) 

were deployed during these studies. Each water gun was 

suspended at a depth of 42 inches (in.) from an anchored 

2.5- by 5-meter pontoon float. The firing of each water gun 

was controlled by a HotShot controller (Real Time Systems, 

Fredericksburg, Texas, USA) tethered to a laptop computer. 

High-pressure air was supplied to each gun by a high-pressure, 

high-volume air compressor (WP 4351 compressor [rated at 

5,000 lb/in2 and 81 standard cubic feet per minute], Sauer 

Compressors USA, Stevensville, Maryland, USA).

Hydrophones are piezoelectric sensors used to determine 

the increase in pressure from the water guns. The impact of 

the blast front moving through the water on a quartz crystal 

produces an electrical voltage in proportion to the pressure 

increase. The blast hydrophone records only the change in 

pressure as a result of the water gun firing. It does not record 

the static pressure. The sensors used were OYO Geospace 

MP-8D Hydrophones with aftermarket connectors by Instantel. They were sampled at a rate of 8,000 to 32,000 samples 

per second (sps) by an Instantel Minimate Pro6 Blasting Seismograph. These sensors have a sensitivity of 0.0237 lb/in2

. 

Underwater blast sensors (UBSs) are piezoelectric 

sensors used to determine the increase in pressure from the 

water guns. The impact of the blast front moving through the 

water produces an electrical voltage on a tourmaline crystal in 

proportion to the pressure increase. The UBS records only the 

change in pressure as a result of the water gun firing. It does 

not record the static pressure. The sensors used were PCB 

Piezotronics W138A01 ICP Underwater Blast Sensors being 

sampled at 8,000 to 32,000 sps by a National Instruments 

NI-9234 C-DAQ data acquisition system linked to a Windows 

laptop running National Instruments Labview Signal Express 

software. These sensors have a sensitivity of 0.02 lb/in2.

The UBSs and blast hydrophones both monitor pressure, 

but they have different operational ranges. UBSs are rated to 

1,000 lb/in2 and are suitable for collecting high-pressure data 

created at closer distances to the water guns. The blast hydrophones are rated to only 47 lb/in2

, but are much more sensitive 

to the 1- to 10-lb/in2 range, and they are more suitable to 

pressures generated at distances generally greater than 30 ft. 

For all setups, the water guns were placed in a fixed 

secured position and depth and fired at a constant pressure. 

Sensors were suspended in the water column a fixed distance 

and depth and moved sequentially in the water surrounding the 

water gun to produce the pressure maps. Five shots were taken 

at each point location, and the maximum value for all five 

shots was recorded. The arithmetic mean of the five maximum 

values recorded at each position was used in the mapping 

figures. 

All acquired data were inspected in the field to ensure 

successful data collection. Maximum values from hydrophones and UBSs were downloaded directly from the instruments into spreadsheet files and also manually recorded. 

September 2012 Study 

The September 2012 study consisted of two separate scenarios, a 1-in3

 and an 80-in3 water gun (fig. 3). Both scenarios 

had similar goals: Determine the basic characteristics of the 

pressure field created by the water guns at maximum pressure 

for each gun, and determine whether any directionality was 

observed in the pressure field. 

 The water gun barge was centered both east-west and 

north-south in the pond, with the water gun suspended so that 

the ejection ports were at a depth of 42 in. The approximate 

distance from shore for the water gun was approximately 50 ft 

east-west and 100 ft north-south. The blast hydrophones were 

suspended at depths of 1.5 ft, 3.5 ft, and 5.5 ft below water 

surface (BWS). During the data collection, the hydrophones 

were advanced across the pond following an approximate 

20-ft grid spacing. The hydrophone measurements were 

confined to the approximately 80-ft-wide center section of the 

approximately 105-ft-wide pond to ensure that the measurements were made over the approximately flat portion of the 

bottom of the pond rather than the sloped edges. Measurements were made in a square-wave-type pattern with the 

hydrophones being advanced to the east or west extent of the 

flat pond surface. The hydrophones were then moved 20 ft in 

the north-south direction to establish a new east-west-trending 

sampling section. This pattern was repeated four times before 

the hydrophones became too close to the water gun to be 

operated safely. UBS data were collected to quantify the area 

within the remaining area surrounding the water gun. This 

constituted 1 iteration consisting of 16 areal data points with a 

value for each of the 3 tested depths. 

The Model 10B 1-in3 water gun scenario consisted 

of a single iteration on the northern end of the pond. The 

1-in3 water gun was suspended vertically beneath the barge 

with the four ejection ports at a depth of 52 in. These ports 

were arranged in a ring attached to the bottom of the cylindrical water gun. One of the ports faced directly toward the north 

end of the pond. All data points were collected at 1,500 lb/in2 

(the maximum operating pressure for the 1-in3 water gun).

The magnitudes of the pressure values (less than 5 lb/in2 

at less than 30 ft) collected for the 1-in3 water gun after 

1 iteration of 16 positions were sufficient to eliminate it as a 

viable gun for creating a large-scale barrier. Testing proceeded 

to the 80-in3 water gun scenario. 
Methods 5

Plan view

20 feet

N

20 feet

Profile view

1.5 feet 1.5 feet

EXPLANATION

Water gun (gun port facing indicated)

Hydrophone buoy

Hydrophone

Exclusion zone

Direction of buoy movement across pond

Figure 3. Data locations for 80-cubic-inch water gun scenario in September 2012. Red water gun indicator shows 

the alternate orientation of the gun ports.
6 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

The S80 80-in3 water gun scenario consisted of four iterations of 16 positions performed on both the north and south 

ends of the pond at a pressure of 2,000 lb/in2 (the maximum 

operating pressure for the 80-in3 water gun). The 80-in3 water 

gun was suspended horizontally beneath the barge with the 

two ejecting ports at a depth of 42 in. 

The orientation of the water gun and resulting direction 

of the ejection ports was changed after two iterations because 

of possible variation in energy output. The ports faced eastwest for the first two iterations, one each on the north and 

south ends of the pond. They faced north-south for the last two 

iterations, one each on the north and south ends of the pond. 

When all four groups are plotted with the water gun held in 

a fixed orientation, the four groups produce a figure with full 

azimuthal coverage around the water gun, which aids in evaluating the directionality of the water gun. 

The location data from the rangefinder were recorded in 

field notebooks from at least four stations located around the 

pond for each hydrophone position. During processing, an x-y 

grid was centered on one of these stations and trigonometric 

and geometric identities were used to locate all of the other 

locations relative to this point. 

July 2013 Study

Three separate scenarios were used for the July 2013 data 

collection: 

1. Fish behavior: Two 80-in3 water guns were set up in the 

UMESC pond to simulate the water gun and equipment 

setup used during the May and June 2013 fish behavior 

experiments.

2. Single gun assessment: One 80-in3 water gun was 

located and fired in the pond to build on the September 

2012 work by better defining the resolution of the 

horizontal and vertical distribution of pressure.

3. Experimental barrier assessment: Two 80-in3 water guns 

were located in the pond to approximate the testing setup 

of a barrier width scenario planned for Morris, Illinois. 

To hasten data collection and better spatially locate the 

hydrophones and UBSs, all underwater hydrophones and UBS 

were suspended from a 40-ft-long PVC boom (fig. 4) that 

would pivot radially from the approximate water gun location. 

Five groups of three sensors each were suspended beneath 

GPS antennas

Hydrophones

Blast sensor

Figure 4. Photo showing hydrophone boom with GPS antennas, hydrophone positions, and blast sensor position indicated.
Methods 7

this boom, with an even horizontal spacing of 10 ft. The sensor group closest to the water guns contained the UBSs; the 

remaining groups were blast hydrophones. To produce the 

five data locations from the two GPS receivers, the data were 

first converted from latitude/longitude format to Universal 

Transverse Mercator (UTM) coordinates. The two farthest 

equipment locations along the receiver boom were determined 

by using the GPS data. The remaining middle three equipment 

locations were determined on the basis of the measured 10-ft 

distance between locations. 

Processed location data were integrated with the average 

maximum values obtained from each data point. These data 

were contoured by using Esri® ArcGIS ArcMAP® (Esri, Inc., 

2013). A kernel smoothing with barriers algorithm was used to 

create pressure maps within the hydrophone and UBS boundaries on each side of the water gun. This kernel interpolation 

model fits a first order polynomial, within specified overlapping neighborhoods, to produce the mapping output, limiting 

instability by using methods similar to ridge regression to 

estimate the regression coefficients. 

Fish Behavior Scenario

Two 80-in3 water guns were on an east-west line located 

145 ft south of the northern pond edge; separation between 

the water guns was approximately 50 ft. The gun ports for 

both guns were set at 42 in. BWS and aligned east-west. Both 

water guns were fired at 1,300 lb/in2. Water gun position was 

established by GPS receivers mounted on the barges supporting the water guns. UBSs were located 20 ft perpendicularly 

north (or south) from the east-west line formed by the two 

water guns, with the hydrophones at 30, 40, 50, and 60 ft from 

the gun. Each hydrophone and blast sensor lateral position was 

recorded at depth settings of 1.5, 3.5, and 5.5 ft (fig. 5).

The PVC boom suspending the sensors was aligned perpendicularly to the east-west gun line and then moved across 

the pond from east to west in approximately 10-ft increments, 

keeping the distance between the end of the boom and the 

east west gun line fixed. This iteration was done first on the 

southern side of the east-west gun line and then on the north 

side (fig. 6). 

40 feet 30 feet

Initial position of boom N

1

2

3

4

5

6

8

7

9

10

11

12

13

Exclusion zone

Water gun

Direction of boom movement

 across pond

Geophone 1

Geophone 2

EXPLANATION

Figure 5. Equipment setup for the fish behavior scenario.
8 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

Single Gun Assessment Scenario

The 80-in3 water gun was fixed in the center of the 

pond (approximately 110 ft) in the north-south direction and 

30 ft from the eastern wall. The gun ports were at a depth of 

42 in BWS and aligned east-west. 

The PVC boom was initially oriented north-south parallel 

to the east wall. The end supporting the UBS was anchored to 

a pivot point on the barge supporting the water gun. From this 

initial position, the PVC boom was swung radially around the 

water gun at 15-degree increments. The UBS was 15 ft from 

the water gun, and the hydrophones were 25, 35, 45, and 55 ft 

from the water gun. The sensors were initially hung at depths 

of 1, 2, and 3 ft. With the sensors at this initial depth setting, 

the boom was swung through 13 positions at increasing angles 

of 15 degrees to complete a 180-degree rotation around the 

water gun barge, with five firings of the water gun collected 

at each position. Once the boom was facing south with its 

length parallel to the east wall, the sensors were repositioned 

to depths of 4, 5, and 6 feet BWS. The boom then was swung 

back, collecting data at the same 15-degree rotation increment 

to return to the original, north-facing position (fig. 6). This 

process constituted one iteration of this scenario. 

This scenario consisted of four trials. The first, second, 

and fourth trial were varied by adjusting the gun pressure to 

1,000, 1,500, and 2,000 lb/in2

 respectively. In the third trial, 

water gun pressure was 1,300 lb/in2, but the gun was suspended 

vertically and the gun port maintained at a depth of 42 in. 

Experimental Barrier Assessment Scenario

The experimental barrier assessment consisted of two 

80-in3 guns separated by an initial distance of 99 ft. Hydrophones were suspended at the midpoint between the two guns. 

Hydrophones were at fixed depths of 1.5, 3.5, and 5.5 ft. Data 

for several iterations were collected by expanding the distance 

between the two guns by 5 ft, moving each gun 2.5 ft to keep 

the hydrophones centered, and varying the pressure of the 

water guns (fig. 7). 

Pressure was varied only on the first distance, 99 ft. 

A pressure of 1,300 lb/in2 is easier for the air compressor to 

maintain when supporting two 80-in3 water guns firing every 

10 seconds; 1,600 lb/in2 is the operational maximum. Testing at 1,300 lb/in2

 indicated that the 5-lb/in2 target value was 

not possible to maintain across the water boundary. All of the 

other iterations were tested at 1,500 lb/in2. 

N

Initial position of boom

Exclusion zone

Water gun

Direction of boom 

 movement around

 water gun

EXPLANATION

Figure 6. Equipment setup for the single gun assessment scenario.
Methods 9

N

Stationary boom

Exclusion zone

Water gun

EXPLANATION

Figure 7. Equipment setup for the experimental barrier evaluation scenario.

Changes for the Experimental Barrier Evaluation Scenario

These data were contoured using a kriging algorithm 

with a search length containing the entire dataset; Surfer® by 

Golden Software was used to produce figures indicating the 

pressure intensity at locations within the pond. Kriging is a 

linear interpolation algorithm used to solve a system of linear 

equations to estimate the value of a regionalized variable at 

a specific point in a random data field. A specific point value 

is a weighted average of the values of that function at nearby 

points with the weights assigned based on distance from the 

chosen point. A solution is found by iterating to minimize the 

variance of the data weights. 

The water guns were fired simultaneously, or as close as 

possible with the equipment limitations, during each data collection period. Because of minor timing variations in the gun 

triggering system, each interaction of the two blast fronts is 

unique. Therefore, each figure shown in the Results section for 

this setup represents only the maximum values from a single 

firing of the water guns, unlike the arithmetic mean of the five 

maximum shots shown in figures for the other scenarios. Each 

figure for this setup represents the shot in which the pressure 

waves met closest to the midpoint between the two guns of the 

3–5 shots taken at each position. The procedure was changed 

in this instance to prevent the artificial improvement of the barrier due to the effects of the averaging process. Averaging the 

results as done in previous trials would increase the extent of 

the 5-lb/in2

 zone artificially because the area where the barrier 

was below the 5-lb/in2 target value was not consistent between 

individual water gun firings. Averaging these data would then 

extend the 5-lb/in2 target area across areas that would not have 

reached that value on any single water gun firing. 
10 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

Results

The following sections of the report are illustrated with 

selected pressure maps of the pond, grouped by study and scenario. These pressure maps (and several additional figures) are 

also presented in appendix 1, in sequential order, to facilitate 

comparison among the different scenarios and studies.

Except for the experimental barrier scenario, all of the 

pressure maps in this report show data points that are derived 

from an arithmetic mean of the five maximum values recorded 

at each position. Figure 8 shows plots of the standard deviation of those five-shot groupings for the September 2012 and 

July 2013 experiments. Standard deviations for these groupings 

increase in close proximity to the water gun firing port and to 

structures in the testing pond such as the sloped wall of the pond 

and the concrete filling structures in the south end of the pond. 

B

0 50

50

60

60

70

80

90

100

110

10

10

20

20

30

30

40

40

0

–5 20 45 70 95 120 150

–15

10

35

60

85

110

140

160

Distance, in feet

Distance, in feet

A

EXPLANATION

Coefficient of

 variation (σ/μ)

0.04

0.35

0.30

0.25

0.20

0.15

0.10

0.09

0.08

0.07

0.06

0.05

0.04

0.03

0

Hydrophone 

 group position

Water gun

in September 2012 (A) and July 2013 (B).

Figure 8. Comparison of two maps showing the spatial distribution of the standard deviation for each five-shot grouping for experiments 

September 2012 Study

1-Cubic-Inch Water Gun Scenario

Data for the 1-in3 water gun scenario are not depicted 

in this report, primarily because the grid spacing and depth 

settings were insufficiently dense to record the extent of the 

5-lb/in2 target value given the much smaller extent of that area 

compared to that for the 80-in3 gun. The differences among 

the three depth settings indicate that the blast front produced 

by the 1-in3 gun is omnidirectional in terms of the horizontal 

distribution of pressure but planar in the vertical dimension, with lower pressures above (1.5 ft BWS) and below 

(5.5 ft BWS) the plane intersecting the gun ports (3.5 ft BWS). 

The 5-lb/in2 threshold was not met in the area sampled, but 

the middle depth setting, 3.5 ft, showed a pressure value over 
Results 11

EXPLANATION

5 pounds per square inch

 contour line

Hydrophone group position

9.5

10.0

9.0

8.5

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5 

Water gun

Pressure, in pounds

 per square inch

–5 20 45 70 95 120 150

–15

10

35

60

85

110

140

160

Distance, in feet

Distance, in feet

Figure 9. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a 

depth of 1.5 feet.

3 lb/in2 out to a distance of approximately 65 ft from the water 

gun. Ultimately, the extent of the pressure field produced by 

the 1-in3 water gun was not large enough to justify the continuation of experiment. 

80-Cubic-Inch Water Gun Scenario

The 80-in3 water gun setup was run as four separate iterations that were then integrated to produce figures 9–11. Data were 

collected on both sides of the pond with the gun ports aligned 

east-west, then north-south. When the data-sets are combined, the 

result is the cruciform pattern shown in figures 9–11. 

Pressure maps for three separate depths (figs. 9–11) show 

variations for depth above, below, and at the level of the water 

gun. The depths above and at the water gun’s depth show the 

greatest radial pressure extent, with the 5-lb/in2

 target level 

extending to approximately 45-ft radius around the gun’s position. The data from the 3.5-ft depth have both the highest pressure (12 lb/in2

 approximately 35 ft from the water gun) and 

the greatest radial extent of the 5-lb/in2 target level with that 

level extending to an approximately 45-ft radius around the 

gun’s position. Data from the 1.5-ft and 5.5-ft depth show both 

lower maximum pressures and smaller radii of the 5-lb/in2

target level, owing to their greater vertical distance from the 

water gun (water gun depth, 42 in). 
12 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

EXPLANATION

5 pounds per square inch

 contour line

Hydrophone group position

9.5

10.0

9.0

8.5

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5 

Water gun

Pressure, in pounds

 per square inch

–5 20 45 70 95 120 150

–15

10

35

60

85

110

140

160

Distance, in feet

Distance, in feet

Figure 10. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a 

depth of 3.5 feet.
Results 13

EXPLANATION

5 pounds per square inch

 contour line

Hydrophone group position

9.5

10.0

9.0

8.5

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5 

Water gun

Pressure, in pounds

 per square inch

–5 20 45 70 95 120 150

–15

10

35

60

85

110

140

160

Distance, in feet

Distance, in feet

Figure 11. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a 

depth of 5.5 feet.
14 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640440 640450 640460 640470 640480

4858770

4858780

4858790

4858800

4858810

4858820

4858830

4858840

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pond

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 12. Pressure map from two 80-cubic-inch water guns fired at 1,300 pounds per square inch, measurements at a 

depth of 3.5 feet.

July 2013 Study

Fish Behavior Scenario

The fish behavior scenario was run as a single iteration with fixed depth settings for hydrophones at 1.5, 3.5 and 

5.5 ft BWS. Data were collected across a roughly 10-ft grid 

both north and south of the line of two guns. No data were 

collected at the center of the two guns because concerns about 

exceeding the pressure limits of the blasting hydrophones. 

Comparisons of data in roughly similar locations relative 

to the locations of the water gun’s firing port show that adding 

a second gun results in roughly twice the pressure compared to 

a single gun (see figs. 12 and 15). Similarly, increases in pressure with depth correlate closely with the single gun results. 

Pressure increases with depth, but the magnitude of the difference among each depth is proportional to the number of guns. 

Single Gun Assessment Scenario

The single gun assessment scenario was run as four separate trials; horizontal gun at 1,000, 1,500, and 2,000 lb/in2

, 

and vertical gun at 1,300 lb/in2. Each trial consisted of one 

180-degree iteration with the hydrophones at 1, 2, and 3 ft BWS 

and one 180-degree iteration with the hydrophones at 

4, 5, and 6 ft BWS. 
Results 15

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 13. Pressure map from 

80-cubic-inch water gun fired at 

1,000 pounds per square inch, 

measurements at a depth of 1 foot.

Trials 1, 2, and 4 differed only in the pressure setting of 

the water gun. Each of these trials showed broadly similar 

results both with each other and with the 80-in3 gun scenario 

in the 2012 study. Pressure increased with depth, and the 

greatest radial extent of the pressure field occurred at the depth 

closest to the firing ports on the water gun. 

The increased data density highlighted several features 

not evident on the 2012 scenario. The radial extent of the 

5-lb/in2

 pressure gradient exceeds the 45-ft limit identified 

in the 2012 scenario at depths close to the firing ports (independent of firing pressure), but this radius is sharply reduced 

by small increases or decreases in depth. Data appear to be 

affected by boundary conditions. During trials 1, 2, and 4, 

there was a large decrease in the overall pressure gradients 

between 4 ft BWS and 5 ft BWS (figs. 16 and 17). This was 

followed by a small, localized increase in the area immediately surrounding the gun at 6 ft BWS (fig. 18). This area 

of increased pressure appears to be due to spreading of the 

pressure front on impact with the bottom or a reflection off 

the bottom. Similar interactions with the bottom of the pond 

also appear on several of the maps where the bottom seems 

to be reducing the strength of the pressure field in a roughly 

45-degree arc southwest of the water gun. 
16 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 14. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 2 feet.
Results 17

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 15. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 3 feet.
18 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 16. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 4 feet.
Results 19

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 17. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 5 feet.
20 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 18. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 6 feet.

The difference in input air pressure did not result in 

large variations among the three trials. The radial extent of 

the 5-lb/in2

 target level at the depth of the firing ports (the 

5-ft BWS maps) differs by less than 5 ft among the three trials. Similar comparisons of the 1-ft BWS and 6-ft BWS maps 

show similar results. The increase in input air pressure results 

in higher pressure gradients closer to the gun, especially comparing the 1,000-lb/in2

 trial and 1,500-lb/in2 trial, but the overall performance of the three trials was very similar. The effect 

of the boundary conditions on these results may be significant. 

Although the pond bottom slopes very shallowly, there is an 

overall change in total depth of about 1 ft from the north end 

to the south end of the testing pond. This depth change combined with the heterogeneous nature of the southern end of 

the pond (transition to concrete filling and holding structures, 

additional pipes and filling apparatus, integrated hydrophones 

and tagging antennas, and so forth) seems to have an effect on 

the shape of the pressure field. 
Results 21

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLAN

Pressure

 per squ

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water g

5 pounds 

 contou

Hydroph

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 19 (top left). Pressure map 

from 80-cubic-inch water gun fired at 

1,000 pounds per square inch, 

measurements at a depth of 5 feet.

Figure 20 (top right). Pressure map 

from 80-cubic-inch water gun fired at 

1,500 pounds per square inch, 

measurements at a depth of 5 feet.

Figure 21 (bottom left). Pressure 

map from 80-cubic-inch water gun 

fired at 2,000 pounds per square inch, 

measurements at a depth of 5 feet.
22 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

Trial 3, the vertical gun scenario at 1,300 lb/in2, was 

evaluated in the field. The results differed in respect to the 

other trials both in radial extent of the 5-lb/in2 target value 

and absolute magnitude of the pressure gradient. When 

compared to trial 1, the absolute magnitude of the pressure 

values showed a decrease of about 30 percent despite firing at 

a higher pressure. Owing to the poor performance of the water 

gun in this orientation and the difficulty of securing the water 

gun in this position for operational testing, this trial was not 

investigated further. 

Experimental Barrier Assessment Scenario

Four hydrophone groups were positioned on the PVC 

boom, which was centered between the two guns. The hydrophones were deployed at depths of 1.5, 3.5, and 5.5 ft BWS. 

The initial separation between the water guns was 99 ft. The 

distance was then increased gradually from 99 ft to 120 ft in 

5-ft nominal increments.

After testing at 99, 104.5, 109.5, 115, and 120 ft of 

separation between the water guns, it was determined that only 

the 99-ft separation maintained sufficient pressure across the 

distance between the two water guns to meet the 5-lb/in2 target 

value. The barriers that were generated in all of the iterations 

confirmed results from previous scenarios in the Morris 2013 

study. Gaps—areas with pressures less than the 5-lb/in2 target 

value—opened first at the upper, 1.5-ft hydrophone group. 

Gaps were the narrowest at the depths closest to the firing 

ports. Gaps on the 5.5-ft group of hydrophones opened at 

wider distances than the 1.5-ft group and remained narrower 

overall. The effect of the boundary conditions on these results 

may be significant, however. The magnitude of the pressure 

field and, therefore, the potential effectiveness as a barrier 

could be either constrained or enhanced depending on the 

water depth at which the water guns are deployed. 

0 10 20 30 40 50 60 70 80 90

–5

–4

–3

–2

Depth, in feet

Distance, in feet

N

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

Pressure, in pounds per square inch

EXPLANATION

Water gun

Hydrophone 

 group position

Figure 22. Pressure map from two 80-cubic-inchwater guns both fired at 1,500 pounds per square inch, separated by 99 feet.
Results 23

–5

–4

–3

–2

Depth, in feet

Distance, in feet

0 10 20 30 40 50 60 70 80 90 100

N

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

Pressure, in pounds per square inch

Water gun

Hydrophone 

 group position

EXPLANATION

Figure 23. Pressure map from two 80-cubic-inch water guns both fired at 1,500 pounds per square inch, separated by 120 feet.
24 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

Summary 

Two studies, one each in September 2012 and July 2013, 

were performed to evaluate the physical characteristics of the 

pressure field created by a water gun fired in a shallow, confined environment. Pressure was evaluated by using blast-rated 

hydrophones and underwater blast sensors. 

The purpose of the September 2012 study was to collect 

data from the pressure field created by a 1-in3 water gun and 

an 80-in3 water gun. The 1-in3 gun produces a horizontally 

omnidirectional and vertically planar pressure wave dispersal pattern that displays sharply reduced pressure above and 

below the plane of the gun ports. The magnitude of the pressure field produced by the 1-in3 gun proved insufficient to be 

solely capable of producing a consistent target 5-lb/in2 threshold. The 80-in3

 gun produces an omnidirectional pressure field 

with a maximum extent of 45 ft for the 5-lb/in2 target values. 

Absolute pressure values increased with increasing depth, but 

the size of the 5-lb/in2 target area decreased with depth. 

The July 2013 study further defined and increased the 

resolution of data collected in the 2012 study to evaluate the 

effectiveness of the 80-in3 water gun(s) in a barrier context 

relative to a 5-lb/in2 target value. Three scenarios were tested: 

fish behavior, single gun assessment, and experimental barrier 

assessment. The fish behavior scenario provided pressure mapping that simulated the area and conditions of previous fish 

behavior studies within the same testing pond, as well as an 

improved understanding of the interaction of two water guns. 

The single gun assessment scenario replicated the 80-in3 gun 

scenario from the 2012 study but with higher data density on 

both the horizontal and vertical planes. This scenario confirmed many of the results of the 80-in3

 gun study in 2012; 

in particular, pressure increase with depth and the absence 

of directionality of the water beyond 10 ft. These data are 

affected by the boundary conditions of the test pond. Variations from established pressure relative to depth trends due to 

the effect of the wave front on the bottom of the pond were 

observed. The experimental barrier evaluation scenario results 

indicate that 99 ft is the maximum extent that two water guns 

fired at 1,500 lb/in2 can maintain a continuous 5-lb/in2 pressure 

field at the depths of the pond.

References

Gross, J.A., Irvine, K.M., Wilmoth, S., Wagner, T.L., Shields, 

P.A., and Fox, J.R., 2013, The effects of pulse pressure 

from seismic water gun technology on Northern Pike: 

Transactions of the American Fisheries Society, v. 142, 

p. 1335–1346.

Hutchinson, D.R., and Detrick, R.S., 1984, Water gun vs. air 

gun—A comparison: Marine Geophysical Researches, v. 6, 

p. 295–310.

Layhee, M.J., Gross, J.A., Parsley, M.J., Romine, J.G., 

Glover, D.C., Suski, C.D., Wagner, T.L., Sepulveda, A.J, 

and Gresswell, R.E., 2013, Asian carp behavior to static 

water gun firing: U.S. Geological Survey Fact Sheet 

2013–3098, 4 p.

Lokkeborg, S., Ona, E., Vold, A., and Salthaug, A., 2012 

Sounds from seismic air guns—Gear- and species-specific 

effects on catch rates and fish distribution: Canadian Journal 

of Fisheries and Aquatic Sciences, v. 69, p. 1278–1291.

Romine, J.G., Jensen, N.R., Parsley, M.J., Gaugush, R.F., 

Severson, T.J., Hatton, T.W., Adams, R.F., and Gaikowski, 

M.P., 2015, Response of Bighead Carp and Silver Carp to 

repeated water gun operation in an enclosed shallow pond: 

North American Journal of Fisheries Management, v. 35, 

no. 3, p. 440–453, DOI:10.1080/02755947.2015.1012279.

Turnpenny, A.W.H., and Nedwell, J.R., 1994, The effects on 

marine fish, diving mammals and birds of underwater sound 

generated by seismic surveys: Fawley Aquatic Research 

Laboratories, Ltd., FARL Report Reference 

FCR 089/94:UKOOA, [50] p.

Wardle, C.S., Carter, T.J., Urquhart, G.G., Johnstone, A.D.F., 

Ziolkowski, A.M., Hampson, G., and Mackie, D., 2001 

Effects of seismic air guns on marine fish: Continental Shelf 

Research, v. 21, p. 1005–1027.
Appendix 1.

Pressure maps produced during all experiments, in sequential 

order, to facilitate comparison between the different scenarios 

and studies.

Abbreviations used in figures: ft, feet; in3, cubic inches; lb/in2, pounds per square inch.
26 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

Plan view

20 feet

N

20 feet

EXPLANATION

Water gun (gun port facing indicated)

Hydrophone buoy

Hydrophone

Exclusion zone

Direction of buoy movement across pond

Profile view

1.5 feet 1.5 feet

Figure 1–1. Data locations for 80-cubic-inch scenario. Red water gun indicator shows the alternate orientation of 

the gun ports. 
Appendix 1 27

EXPLANATION

5 pounds per square inch

 contour line

Hydrophone group position

9.5

10.0

9.0

8.5

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5 

Water gun

Pressure, in pounds

 per square inch

–5 20 45 70 95 120 150

–15

10

35

60

85

110

140

160

Distance, in feet

Distance, in feet

Figure 1–2. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a 

depth of 1.5 feet.
28 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

EXPLANATION

5 pounds per square inch

 contour line

Hydrophone group position

9.5

10.0

9.0

8.5

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5 

Water gun

Pressure, in pounds

 per square inch

–5 20 45 70 95 120 150

–15

10

35

60

85

110

140

160

Distance, in feet

Distance, in feet

Figure 1–3. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch measurements at a 

depth of 3.5 feet.
Appendix 1 29

EXPLANATION

5 pounds per square inch

 contour line

Hydrophone group position

9.5

10.0

9.0

8.5

8.0

7.5

7.0

6.5

6.0

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5 

Water gun

Pressure, in pounds

 per square inch

–5 20 45 70 95 120 150

–15

10

35

60

85

110

140

160

Distance, in feet

Distance, in feet

Figure 1–4. Pressure map from 80-cubic-inch water gun fired at 2,000 lpounds per square inch measurements at a 

depth of 5.5 feet.
30 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

40 feet 30 feet

Initial position of boom N

1

2

3

4

5

6

8

7

9

10

11

12

13

Exclusion zone

Water gun

Direction of boom movement

 across pond

Geophone 1

Geophone 2

EXPLANATION

Figure 1–5. Equipment setup for the fish behavior scenario.
Appendix 1 31

640440 640450 640460 640470 640480

4858770

4858780

4858790

4858800

4858810

4858820

4858830

4858840

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pond

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–6. Pressure map from two 80-cubic-inch guns both fired at 1,300 pounds per square inch, measurements at a 

depth of 1.5 feet.
32 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640440 640450 640460 640470 640480

4858770

4858780

4858790

4858800

4858810

4858820

4858830

4858840

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pond

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–7. Pressure map from two 80-cubic-inchwater guns both fired at 1,300 pounds per square inch, measurements at 

a depth of 3.5 feet.
Appendix 1 33

640440 640450 640460 640470 640480

4858770

4858780

4858790

4858800

4858810

4858820

4858830

4858840

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pond

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–8. Pressure map from two 80-cubic-inch water guns both fired at 1,300 pounds per square inch, measurements at a 

depth of 5.5 feet.
34 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

N

Initial position of boom

Exclusion zone

Water gun

Direction of boom 

 movement around

 water gun

EXPLANATION

Figure 1–9. Equipment setup for the single gun assessment scenario.
Appendix 1 35

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–10. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 1 foot.
36 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–11. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 2 feet.
Appendix 1 37

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–12. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 3 feet.
38 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–13. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 4 feet.
Appendix 1 39

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1-14. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch, measurements at a 

depth of 5 feet.
40 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–15. Pressure map from 80-cubic-inch water gun fired at 1,000 pounds per square inch measurements at a 

depth of 6 feet.
Appendix 1 41

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–16. Pressure map from 80-cubic-inch water gun fired at 1,500 pounds per square inch, measurements at a 

depth of 1 foot.
42 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–17. Pressure map from -cubic-inch water gun fired at 1,500 pounds per square inch, measurements at a 

depth of 2 feet.
Appendix 1 43

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–18. Pressure map from 80-cubic-inch water gun fired at 1,500 pounds per square inch, measurements at a depth 

of 3 feet.
44 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

EXPLANATION

Pressure, in pounds

 per square inch

Figure 1–19. Pressure map from 80-cubic-inch water gun fired at 1,500 pounds per square inch, measurements at a 

depth of 4 feet.
Appendix 1 45

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–20. Pressure map from 80-cubic-inch water gun fired at 1,500 pounds per square inch, measurements 

at a depth of 5 feet.
46 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–21. Pressure map from 80-cubic-inch water gun fired at 1,500 pounds per square inch, measurements at a 

depth of 6 feet.
Appendix 1 47

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–22. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a depth 

of 1 foot.
48 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–23. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a 

depth of 2 feet.
Appendix 1 49

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–24. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a 

depth of 3 feet.
50 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–25. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a 

depth of 4 feet.
Appendix 1 51

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–26. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a 

depth of 5 feet.
52 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

640455 640460 640465 640470

4858785

4858790

4858795

4858800

4858805

4858810

4858815

Universal Transverse Mercator (UTM), Zone 15N, easting, in meters

Universal Transverse Mercator (UTM), Zone 15N, northing, in meters

EXPLANATION

Pressure, in pounds

 per square inch

80

100

60

40

30

20

15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

Water gun

5 pounds per square inch

 contour line

Hydrophone group position

Figure 1–27. Pressure map from 80-cubic-inch water gun fired at 2,000 pounds per square inch, measurements at a 

depth of 6 feet.
Appendix 1 53

N

Stationary boom

Exclusion zone

Water gun

EXPLANATION

Figure 1–28. Equipment setup for the experimental barrier evaluation scenario.
54 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

0 10 20 30 40 50 60 70 80 90

–5

–4

–3

–2

Depth, in feet

Distance, in feet

N

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

Pressure, in pounds per square inch

EXPLANATION

Water gun

Hydrophone 

 group position

Figure 1–29. Pressure map from two 80-cubic-inch water guns both fired at 1,300 pounds per square inch, separated by 99 feet.

0 10 20 30 40 50 60 70 80 90

–5

–4

–3

–2

Depth, in feet

Distance, in feet

N

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

Pressure, in pounds per square inch

EXPLANATION

Water gun

Hydrophone 

 group position

Figure 1–30. Pressure map from two 80-cubic-inch water guns fired at 1,500 pounds per square inch, separated by 99 feet.
Appendix 1 55

–5

–4

–3

–2

Depth, in feet

Distance, in feet

0 10 20 30 40 50 60 70 80 90 100

N

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

Pressure, in pounds per square inch

EXPLANATION

Water gun

Hydrophone 

 group position

Figure 1–31. Pressure map from two 80-cubic-inch water guns both fired at 1,500 pounds per square inch, separated by 104 feet.

–5

–4

–3

–2

Depth, in feet

Distance, in feet

0 10 20 30 40 50 60 70 80 90 100

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

Pressure, in pounds per square inch

EXPLANATION

Water gun

Hydrophone 

 group position

N

Figure 1–32. Pressure map from two 80-cubic-inch water guns both fired at 1,500 pounds per square inch, separated by 109.5 feet.
56 Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin

–5

–4

–3

–2

Depth, in feet

Distance, in feet

0 10 20 30 40 50 60 70 80 90 100

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

Pressure, in pounds per square inch

EXPLANATION

Water gun

Hydrophone 

 group position

N

Figure 1–33. Pressure map from two 80-cubic-inch water guns both fired at 1,500 pounds per square inch, separated by 115 feet.

–5

–4

–3

–2

Depth, in feet

Distance, in feet

0 10 20 30 40 50 60 70 80 90 100

N

2

2.5

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

8.5

9

9.5

10

Pressure, in pounds per square inch

Water gun

Hydrophone 

 group position

EXPLANATION

Figure 1–34. Pressure map from two 80-cubic-inch water guns both fired at 1,500 pounds per square inch, separated by 120 feet.

Adams and Morrow—Geophysical Investigation of the Pressure Field Produced by Water Guns at a Pond Site in La Crosse, Wisconsin—Open-File Report 2015–1130

ISSN 2331-1258 (online)

http://dx.doi.org/10.3133/ofr20151130