U.S. Department of the Interior

U.S. Geological Survey

Open-File Report 2007–1187

Prepared in cooperation with the Electric Power Research Institute

Evaluation of Acoustic Doppler Current Profiler to 

Measure Discharge at New York Power Authority’s 

Niagara Power Project, Niagara Falls, New York
Cover. Aerial image of Niagara River, Forebay (diversion) Canal and the Lewiston Reservoir at the New York Power Authority’s 

Niagara Project, Niagara Falls, New York. (Source of the graphic is from the NYS GIS Clearinghouse.)
Evaluation of Acoustic Doppler Current Profiler to 

Measure Discharge at New York Power Authority’s 

Niagara Power Project, Niagara Falls, New York 

By Henry J. Zajd, Jr. 

Prepared in cooperation with the Electric Power Research Institute 

Open-File Report 2007–1187 

U.S. Department of the Interior 

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

DIRK KEMPTHORNE, Secretary 

U.S. Geological Survey 

Mark D. Myers, Director 

U.S. Geological Survey, Reston, Virginia: 2007 

For more information on the USGS—the Federal source for science about the Earth, 

its natural and living resources, natural hazards, and the environment: 

World Wide Web: http://www.usgs.gov 

Telephone: 1-888-ASK-USGS 

Suggested citation: 

Zajd, H.J., Jr., 2007, Evaluation of Acoustic Doppler Current Profiler to measure discharge at New York 

Power Authority’s Niagara Power Project, Niagara Falls, New York: U.S. Geological Survey Open-File 

Report 2007–1187, 21 p., Online Only

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement 

by the U.S. Government. 

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report. 

ii
Contents 

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

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

Physical Setting ..............................................................................................................................................................5

Purpose and Scope ........................................................................................................................................................6

Methods ...............................................................................................................................................................................6

Instrumentation...............................................................................................................................................................6

Measurement Procedures..........................................................................................................................................12

New York Power Authority Method of Calculating Water Diversion..................................................................13

Acoustic Doppler Current Profiler Measurements in Relation to New York Power Authority 

 Calculations...................................................................................................................................................................14

Summary and Conclusions .............................................................................................................................................18

Acknowledgments............................................................................................................................................................18

References Cited ..............................................................................................................................................................19

Appendix. Acoustic Doppler Current Profiler transect start and end times and durations, recorded 

channel velocities, flow directions, and total discharges, at New York Power Authority Niagara Power 

Project generation facility, Niagara Falls, N.Y., November 6–8, 2006.....................................................................20

Figures 

1. Map showing location of Buffalo and Niagara Falls, Lake Erie and Lake Ontario, and relation 

to study area near New York Power Authority Niagara Power Project generation facility, 

Niagara Falls, N.Y. ................................................................................................................................................3 

2. Map showing location of Lewiston Reservoir, Forebay Canal, Robert Moses Power Plant, and 

“Pant Leg” diversion channel area near New York Power Authority Niagara Power Project 

generation facility, Niagara Falls, N.Y. .............................................................................................................4 

3. Map showing location of “Pant Leg” diversion channel and walkway discharge measuring 

section at the New York Power Authority Niagara Power Project generation facility, 

Niagara Falls, N.Y. ................................................................................................................................................5 

4. Photographs showing: (A) Acoustic Doppler Current Profiler (ADCP) mounted on a tethered 

trimaran platform that floats on the water surface to measure water velocity and (B) ADCP 

floating in “Pant Leg” diversion channel downstream from walkway bridge at New York Power 

Authority Niagara Power Project generation facility, Niagara Falls, N.Y. ................................................7 

5. Graphs showing examples of graphical output (profiles) from Acoustic Doppler Current Profiler 

(ADCP) showing measured water velocity magnitude, in feet per second (ft/s), and direction, 

in degrees (°), based on raw ADCP data collected at “Pant Leg” diversion channel near 

New York Power Authority Niagara Power Project generation facility, Niagara Falls, N.Y., 

November 7, 2006..................................................................................................................................................9 

6. Photographs showing measurement setup: Price-AA current meter and sounding weight, 

E-reel, and E-crane used for standard U.S. Geological Survey current-meter discharge 

measurement from bridges and used at the “Pant Leg” diversion channel near New York 

Power Authority Niagara Power Project generation facility, Niagara Falls, N.Y. .................................10 

iii
7. Vertical section of water column showing locations of individual Price-AA current-meter 

measurements from bridge walkway near the end of Niagara Power Authority “Pant Leg” 

diversion channel, November 7, 2006, 10:30–12:05 Eastern Standard Time.............................................11 

8. Plots showing Acoustic Doppler Current Profiler discharge measurements and New York 

Power Authority (NYPA)-calculated discharges obtained during the four measurement sessions 

at “Pant Leg” diversion channel near NYPA Niagara Power Project generation facility, 

Niagara Falls, N.Y., November 6–8, 2006 ........................................................................................................15 

9. Niagara River Diversion histogram showing 2005–2006 calendar year and discharge rates 

during Acoustic Doppler Current Profiler measurements in “Pant Leg” diversion channel 

on November 6, 7, and 8, 2006, near New York Power Authority Niagara Power Project 

generation facility, Niagara Falls, N.Y. ...........................................................................................................16 

10. Vertical section of “Pant Leg” diversion channel showing area for which the discharge was 

measured, area for which the discharge theoretically should have been estimated, and area 

where the discharge was estimated...............................................................................................................17 

Table 

1. Data from comparison of Acoustic Doppler Current Profiler discharge measurements with 

discharge calculations by New York Power Authority at Niagara Power Project generation 

facility, Niagara Falls, N.Y., November 6–8, 2006 ..........................................................................................12 

Conversion Factors 

Multiply By To obtain 

Length 

inch (in.) 2.54 centimeter (cm) 

foot (ft) 0.3048 meter 

mile (mi) 1.609 kilometer 

Flow rate 

cubic foot per second (ft3/s) 0.02832 cubic meter per second 

Horizontal coordinate information is referenced to North American Datum of 1983 (NAD 83).

iv
Evaluation of Acoustic Doppler Current Profiler to 

Measure Discharge at New York Power Authority’s 

Niagara Power Project, Niagara Falls, New York 

By Henry J. Zajd, Jr. 

Abstract 

The need for accurate real-time discharge in the International Niagara River hydro power 

system requires reliable, accurate and reproducible data. The U.S. Geological Survey has been 

widely using Acoustic Doppler Current Profilers (ADCP) to accurately measure discharge in 

riverine channels since the mid-1990s. The use of the ADCP to measure discharge has remained 

largely untested at hydroelectric-generation facilities such as the New York Power Authority’s 

(NYPA) Niagara Power Project in Niagara Falls, N.Y. This facility has a large, engineered 

diversion channel with the capacity of high volume discharges in excess of 100,000 cubic feet per 

second (ft3

/s). Facilities such as this could benefit from the use of an ADCP, if the ADCP discharge 

measurements prove to be more time effective and accurate than those obtained from the flowcalculation techniques that are currently used. 

Measurements of diversion flow by an ADCP in the “Pant Leg” diversion channel at the 

Niagara Power Project were made on November 6, 7, and 8, 2006, and compared favorably 

(within 1 percent) with those obtained concurrently by a conventional Price-AA current-meter 

measurement during one of the ADCP measurement sessions. The mean discharge recorded during 

each 2-hour individual ADCP measurement session compared favorably with (3.5 to 6.8 percent 

greater than) the discharge values computed by the flow-calculation method presently in use by 

NYPA. The use of ADCP technology to measure discharge could ultimately permit increased 

power-generation efficiency at the NYPA Niagara Falls Power Project by providing improved 

predictions of the amount of water (and thus the power output) available. 

Introduction 

The New York Power Authority (NYPA) and its Canadian counterpart, Ontario Hydro of 

Canada, abide by an international treaty on the amounts of water that may be diverted from the 

upper Niagara River to the two hydropower plants. Accurate measurements of the quantity of water 

diverted from the Niagara River for hydroelectric power generation are needed to fulfill the terms 

of this agreement. NYPA wants to know whether Acoustic Doppler technology is suitable for this 

application. Therefore, in November 2006, the U.S. Geological Survey (USGS), in cooperation 

with the Electric Power Research Institute (EPRI) and NYPA, ran a 3-day test to assess the 

accuracy and feasibility of using an Acoustic Doppler Current Profiler (ADCP) to measure 

discharge in the “Pant Leg,” a large, engineered diversion channel at the NYPA Niagara Power 

Project, under high-flow conditions (figs. 1 and 2). The availability of real-time discharge data 

1
from this location would improve the prediction of the amount of water (and thus the power output) 

available to meet power-generation requirements and could increase the efficiency of watermanagement administration for both countries. 

2
Figure 1. Location of Buffalo and Niagara Falls, Lake Erie and Lake Ontario, and relation 

to study area near New York Power Authority Niagara Power Project generation facility, 

Niagara Falls, N.Y. 

3
Figure 2. Location of Lewiston Reservoir, Forebay Canal, Robert Moses Power Plant, and 

“Pant Leg” diversion channel area near New York Power Authority Niagara Power Project 

generation facility, Niagara Falls, N.Y. (Source of the graphic is from the NYS GIS Clearinghouse.) 

4
Physical Setting 

The Niagara River forms the international boundary between the Province of Ontario and 

the State of New York (fig. 1). It begins at the mouth of Lake Erie at Buffalo, N.Y., and flows 

35.4 mi northward to Lake Ontario. NYPA’s Niagara Power Project diverts river water from the 

area just upstream of Niagara Falls into two 46-ft-wide by 66-ft-high buried, arched conduits that 

carry the water 4.3 mi to a single open channel called the “Pant Leg” (fig. 2), which, in turn, 

conveys water 1,700 ft to the Forebay Canal (fig. 2). Depending on the time of day and the day of 

the week, either all of the water that exits the “Pant Leg” diversion channel is routed through the 

turbines at the Robert Moses Power Plant at the western end of the Forebay Canal (fig. 2), or some 

part of that water is pumped up into the adjacent Lewiston Reservoir for later release and power 

generation, first at the Lewiston Reservoir Power Plant, then at the Robert Moses Power Plant. 

The “Pant Leg” channel (fig. 3) is the only reach along this diversion at which 

measurements of discharge can be made; therefore, it was the focus of this study. This channel is 

excavated into dolomite bedrock and has vertical walls more than 100 ft high; water depth ranges 

from 45 to 60 ft, depending on power-generation and pumping schedules. The width of this channel 

at the point where the two conduits converge is 250 ft and increases to 300 ft at the “walkway 

bridge” that crosses the channel 1,300 ft downstream from the opening of the conduits. 

Downstream from the bridge, the channel widens to more than 400 ft where it joins the Forebay 

Canal (fig. 3). 

Figure 3. Location of “Pant Leg” diversion channel and walkway discharge measuring section at 

the New York Power Authority Niagara Power Project generation facility, Niagara Falls, N.Y. 

5
Purpose and Scope 

This report describes the methods and discusses results of the 3-day tests. The data from 

each run on each of the 3 days are tabulated in the appendix. 

Methods 

ADCP and standard current-meter measurements were made from the walkway bridge that 

crosses the “Pant Leg” diversion channel because this is the only location at which both types of 

discharge measurements could be made. Standard USGS procedures were used for both types of 

measurements, as described below. 

Instrumentation 

The acoustic measurements were made by an RD Instruments 600-kilohertz (kHz) ADCP 

mounted to an Ocean Science trimaran platform that was tethered to the bridge (figs. 4A and 4B). 

The ADCP unit had a radio link to a laptop computer on the walkway bridge (fig. 4) for 

transmission of data. The trimaran platform, to which control rope and additional safety rope were 

attached, was lowered to the water surface from the downstream side of the walkway bridge by a 

crane supplied by NYPA. The trimaran platform was then allowed to float about 100 ft downstream 

from the walkway bridge to avoid the effect of any interference caused by the walkway bridge 

piers. The trimaran platform was towed slowly (about 1 ft per second) across the “Pant Leg” 

channel by a technician walking across the bridge while the ADCP recorded individual vertical 

depth and velocity profiles (ensembles) every 1.2 seconds according to the “ping” rate (the time 

interval between sound-wave pulses from the ADCP equipment). The relatively slow rate of 

traverse across the channel allowed a large number of depth and velocity measurements to be made 

and thereby maximized the resolution and, therefore, the accuracy of the computed total discharge. 

6
Figure 4. (A) Acoustic Doppler Current Profiler (ADCP) mounted on a tethered trimaran platform 

that floats on the water surface to measure water velocity and (B) ADCP floating in “Pant Leg” 

diversion channel downstream from walkway bridge at New York Power Authority Niagara Power 

Project generation facility, Niagara Falls, N.Y. 

7
ADCP’s measure water velocity acoustically by transmitting pings (sound-wave pulses) 

into the water column at a specific frequency and recording the time differential for the arrival of 

the reflected sound from particles suspended in the water. If the particle reflectors are moving 

closer to or further away from the instrument transducers, the return frequency is Doppler shifted, 

The ADCP is designed to measure this Doppler shift and compute the velocity and direction of the 

particle and by extension, the water’s velocity (RD Instruments, Inc., 1989). The ADCP is designed 

to measure three-dimensional velocity profiles, as well as the depth and path the platform make as 

it navigates the channel. The ADCP measures water velocity in many small “bins” (measurements 

of velocity magnitude and direction in a given vertical distance in successive vertical subsections 

for each individual ping) in each vertical ensemble as the instrument is moved across the channel 

(fig. 5). The individual bins of velocity and area in each ensemble are summed by the ADCP to 

produce a total discharge for that ensemble. The recorded discharges from all ensembles are then 

summed to obtain the total discharge across the channel during the measurement period. These 

discharge values are added to estimates of discharge along the wetted perimeter (edges and bottom) 

and near the water surface of the channel, which the instrument is unable to measure directly 

(RD Instruments, Inc., 1989; Simpson and Oltmann, 1992; Morlock, 1996; and Simpson, 2002). 

8
Figure 5. Examples of graphical output (profiles) from Acoustic Doppler Current Profiler (ADCP) 

showing measured water velocity magnitude, in feet per second (ft/s), and direction, in degrees (°), 

based on raw ADCP data collected at “Pant Leg” diversion channel near New York Power Authority 

Niagara Power Project generation facility, Niagara Falls, N.Y., November 7, 2006. (A) Velocity 

magnitude. (B) Velocity direction. 

9
The discharge measurement made for comparison with the ADCP measurements was made 

by a Standard Price-AA current meter suspended by a cable with a 150-pound sounding weight 

attached to a USGS “E-reel” and bridge crane (fig. 6). The Price-AA current meter consists of a 

rotor with six cone-shaped cups mounted on a stainless-steel shaft that spin on a pivot. As the water 

passes by, an electrical contact is made each time the meter cups make a full revolution; thus, the 

number of revolutions per time unit is a function of the water velocity. Water velocity was 

measured at two locations, 20 and 80 percent of total depth, in each vertical measuring location 

along the walkway (every 10 ft) in the channel cross section (fig. 7). 

Figure 6. Measurement setup: Price-AA current meter and sounding weight, E-reel, and E-crane 

used for standard U.S. Geological Survey current-meter discharge measurement from bridges and 

used at the “Pant Leg” diversion channel near New York Power Authority Niagara Power Project 

generation facility, Niagara Falls, N.Y. 

10
Figure 7. Vertical section of water column showing locations of individual Price-AA current-meter 

measurements from bridge walkway near the end of Niagara Power Authority “Pant Leg” diversion 

channel, November 7, 2006, 10:30–12:05 Eastern Standard Time. 

The Price-AA current meter was checked before and after the discharge measurement 

through a standardized spin test in air to indicate whether the cups were able to rotate freely and 

smoothly until all motion had stopped. This test was timed, and the results are compared with the 

standard minimum spin time of 1 minute 45 seconds, as prescribed in Rantz (1982). In this study, 

the meter spun for 2 minutes 45 seconds before the measurement and spun freely afterward; it also 

showed no sign of damage upon removal from the water after the measurement was completed. 

The area corresponding to each vertical velocity measurement that is used in the computation of 

each section’s discharge equals the depth at that section multiplied by the average width, which is 

one-half the distance between the previous vertical section and the next adjacent vertical section 

(fig. 7). The discharge in each section is calculated as the computed area of that section multiplied 

by the respective mean velocity in the section. The mean velocity is the mathematical average of 

the two measured velocities in the section. The total discharge for the channel is then calculated as 

the sum of values for all sections across the channel, as prescribed in Rantz (1982). 

11
Measurement Procedures 

Four ADCP measurement sessions from the “Pant Leg” walkway were held during 

November 6–8, 2006. Each session consisted of 12 to 17 individual ADCP measurements over a 

period of about 2 hours. ADCP water modes 12 SB (small bin size, 25 cm) and RB (regular bin 

size, 50 cm) were chosen for the first session for their general applicability in a variety of channel 

configurations (U.S. Geological Survey, 2003). Subsequent experimentation with other bin-size 

settings on November 6, 2006, revealed that mode 12RB was optimal for this site. Therefore, the 

other three sessions (November 7–8) were made in mode 12RB. 

ADCP measurements were made in accordance with published USGS quality-assurance 

procedures (Oberg and others, 2005). The three major steps are (1) verification of communication 

between the ADCP and the ADCP software provided on a laptop; (2) performance of a set of 

pre-described, standard diagnostic tests to ensure that the equipment is operational; (3) selection of 

an appropriate operational water mode for the ADCP according to channel configuration, depth and 

velocity. The average discharge for each session (the mean for the several measurements; see 

appendix) was used to represent discharge over the entire ADCP measurement session. These 

average ADCP discharges were then compared with the NYPA average for discharge estimates 

made over the same time period (see next section, “New York Power Authority Method of 

Calculating Water Diversion”); those estimates are based on water-level changes and turbine 

efficiencies on an hourly basis (table 1). In addition, one standard USGS current-meter 

measurement was made on the morning of November 7, 2006 for comparison with the concurrent 

ADCP measurement session as a quality-assurance test for the discharges reported by the 

ADCP method. 

Table 1. Data from comparison of Acoustic Doppler Current Profiler discharge measurements with 

discharge calculations by New York Power Authority1

 at Niagara Power Project generation facility, 

Niagara Falls, N.Y., November 6–8, 2006. 

[ADCP, Acoustic Doppler Current Profiler; NYPA, New York Power Authority. All discharge (Q) values are in cubic 

feet per second.] 

Date, time (hhmm, eastern standard), and data source 

11/06/2006 

1445-1604 

11/07/2006 

1017-1202 

11/07/2006 

1425-1554 

11/08/2006 

1017-1112 

Statistic ADCP NYPA ADCP NYPA ADCP NYPA ADCP NYPA 

Number of measurements 

 per session 

12 2 12 3 17 2 12 2 

Range of Q per session 85,500 - 

94,400 

83,400 - 

84,700 

77,000 - 

89,300 

74,400 - 

83,100 

87,100 - 

95,400 

87,300 - 

87,700 

85,300 - 

91,500 

83,000 - 

85,100 

Mean Q per session 89,700 84,000 83,600 78,700 90,600 87,500 88,500 84,000 

ADCP value minus NYPA 

value, in percent 

+6.8 +6.2 +3.5 +5.4 

1

Discharge calculations are hourly and based on an algorithm used by NYPA that includes data from the Forebay and 

Lewiston Reservoir, and turbine efficiency at Robert Moses and Lewiston powerplants (James Ellis, New York Power 

Authority, written commun., December 18, 2006). 

12
New York Power Authority Method of Calculating Water Diversion 

Discharge from the “Pant Leg” channel can be calculated from the Robert Moses power 

plant output and the changes in the volume of water stored in the Forebay Canal and the Lewiston 

Reservoir. These river-diversion calculations are made hourly and are based on water-elevation 

readings to estimate retained water (pondage) as well as the plant’s power generation. Watersurface elevation is monitored at the southwestern corner in the following three locations: (1) the 

Robert Moses power plant tailrace (Niagara River), (2) the Forebay Canal, and (3) the upper 

(Lewiston) reservoir (fig. 2). 

Pondage for the two areas is calculated from the respective elevation readings and data 

tables. The pondage calculation represents the water volume, derived from elevation differences 

between the beginning and ending hourly measurements. These pondage volumes are then used in 

the following calculations to obtain the discharge in the “Pant Leg” diversion channel: 

Reservoir pondage for hour = Pond (ResBH) – Pond (ResEH), (1) 

[function based on volumetric table] 

Forebay pondage for hour = Pond (FbayBH) – Pond (FbayEH), (2) 

[function based on plant volumetric table] 

Robert Moses plant discharge for hour = (RMHDAvg MW) (3) 

[Function based on Gibson Test and plant megawatts (MW) during the 

period. Note that minute-to-minute scans of water elevations provide 

input head to estimate turbine efficiency for water to power 

output calculation.] 

“Pant Leg” diversion discharge for hour = Robert Moses plant discharge for hour – 

Reservoir pondage – Forebay pondage (4) 

where 

ResBH = Reservoir beginning of hour elevation

ResEH = Reservoir end of hour elevation

FbayBH = Forebay beginning of hour elevation

FbayEH = Forebay end of hour elevation

RMHDAvg = Robert Moses Plant head average for hour 

MW = Megawatt

13
Three factors can lead to errors in the “Pant Leg” diversion calculation: 

1. The assumption that water surfaces are level when dynamic load changes (from 400 to 

2,400 megawatts) and ice can create oscillations that result in errors in volume 

calculation. The degree of error depends on the accuracy of the beginning and ending 

water-level-elevation readings, which might be affected by lag times and oscillating 

water levels. 

2. The dependence of plant-control commands (opening and closing of water-turbine 

gates) on the diversion-calculation algorithms to establish the next water-level set point. 

3. The dependence of the calculation on accurate indexing of individual turbine 

performance is currently based on only limited test data. 

Opportunities to refine plant output control (power generation) and reduce potential errors in 

the present discharge-measurement system are a key reason why the ADCP measurement may 

benefit plant operations. (Thomas Key, Electric Power Research Institute, written commun., 

February 2007). 

Acoustic Doppler Current Profiler Measurements in Relation to 

New York Power Authority Calculations 

Data from all four ADCP measurement sessions (starting and ending time, test duration, 

channel velocity, flow direction, and total discharge) are given in the appendix; the NYPAcomputed discharges are given for comparison with the ADCP averaged discharges in table 1. 

Comparison of the ranges of discharges obtained by the ADCP with those obtained by NYPA 

calculations (table 1) indicates that each ADCP session’s discharge varied more widely than the 

two or three hourly calculated discharges reported by NYPA (fig. 8). The ADCP measurements 

reflected 37 percent of the entire range of power-generation conditions that NYPA calculated in 

2005–06 (fig. 9) (Thomas Key, Electric Power Research Institute, written commun., February 3, 

2007). The average of the ADCP measurement-session discharges ranged from 3.5 to 6.8 percent 

greater than those computed by NYPA for the same period (table 1). The difference between 

average ADCP discharge and the concurrent discharge measured by current meter on November 7, 

2006 was within 1 percent (84,000 ft3

/s for the ADCP measurement, and 83,600 ft3/s for the current 

meter measurement). 

14
Figure 8. Acoustic Doppler Current Profiler discharge measurements and New York Power 

Authority (NYPA)-calculated discharges obtained during the four measurement sessions at 

“Pant Leg” diversion channel near NYPA Niagara Power Project generation facility, Niagara 

Falls, N.Y., November 6–8, 2006. 

15
Figure 9. Niagara River Diversion histogram showing 2005–2006 calendar year and discharge 

rates during Acoustic Doppler Current Profiler measurements in “Pant Leg” diversion channel on 

November 6, 7, and 8, 2006, near New York Power Authority Niagara Power Project generation 

facility, Niagara Falls, N.Y. 

The discharge close to the channel wall, for an ADCP measurement, cannot be measured 

accurately because one or more of the four beams from the ADCP impinges on the vertical wall. 

This beam impingement gives an erroneous value for the measured velocity along the vertical 

walls; therefore, an erroneous discharge. Standardized methods of the USGS, along with the 

recommendations of the ADCP manufacturer, imply that accurate measurements near the edges of 

vertical-walled channels can be made no closer than a horizontal distance equal to the depth of the 

water along that channel’s edge. Guidelines by Fulford and Sauer (1986) and Simpson and 

Oltmann (1992) call for the first or last measurement of velocity, that is not affected by beam 

impingement along either edge of the channel wall, to be used in the estimation of discharge. For 

example, the depth of water along the channel walls in the “Pant Leg” diversion channel ranged 

from 45 to 50 ft; thus, the first and last reliable measurement locations, according to the above 

recommendation, would be 45 to 50 ft from the edge of the channel. 

The “Pant Leg” diversion-channel width at the walkway bridge is just over 300 ft with the 

water depth along the channel walls of 45 to 50 ft. Following the above guidelines meant only 

67 percent of the channel width could be measured. Testing of this guideline on November 6, 2006, 

revealed that beam impingement occurred at 20 ft from the left edge of the vertical wall in the 

“Pant Leg” diversion channel, and at 30 ft from the right edge, rather than at the 45 to 50 ft 

prescribed by the standard method (fig. 10). The reduced distance along the “Pant Leg” Channel, 

16
20 to 30 ft versus 45 to 50 ft, increased the percent of measured discharge to about 80 percent. 

Therefore, this testing increased the accuracy of the ADCP discharge measurement, by decreasing 

the amount of estimated discharge (fig. 10). 

Figure 10. Vertical section of “Pant Leg” diversion channel showing area for which the discharge 

was measured, area for which the discharge theoretically should have been estimated, and area 

where the discharge was estimated.

In contrast to the above procedure, the current-meter method of discharge measurement 

required an estimate of discharge within only 5 ft of the left channel wall. A comparison of the 

ADCP edge discharge value was made with current-meter measurements for the same distance 

(20 ft), near the left edge of the “Pant Leg” diversion channel and indicated a difference of 

less than 1 percent (5,500 ft3

/s for the ADCP, and 5,520 ft3/s for the current meter). The standard 

criteria used, and the field and channel conditions at the time of the measurement, indicate 

that the measurements by both methods could be rated as “good” (95-percent confidence or 

5-percent error). 

17
Summary and Conclusions 

The U.S. Geological Survey (USGS), in cooperation with the Electric Power Research 

Institute (EPRI) and New York Power Authority (NYPA) tested the effectiveness and accuracy of 

using an Acoustic Doppler Current Profiler (ADCP) to make discharge measurements in a highvolume water-diversion channel at the NYPA Niagara Falls Power Project at Niagara Falls, N.Y. 

ADCP measurements were made over 37 percent of the range of power-generation conditions that 

NYPA had observed between 2005 and 2006. The ADCP was able to measure high-volume 

discharges accurately in this power-diversion channel. One standard USGS Price-AA current 

meter on November 7, 2006, made concurrently with a series of ADCP measurements, indicated 

that the ADCP results were within 1 percent of those obtained by the current-meter technique. The 

current meter measurement was made as a quality-assurance test for the discharges reported by the 

ADCP method. 

The number of measurements made by the ADCP exceeded the number of hourly 

calculations normally computed by NYPA; therefore, the ADCP method captured more of the 

variability in discharge in the “Pant Leg” diversion channel during each 2-hour measurement 

period. A comparison of the mean ADCP discharge measured during each of the four ADCP 

measurement sessions with the mean discharge values calculated by NYPA through their standard 

procedures indicated a difference of 3.5 to 6.8 percent. These results indicate that use of an ADCP 

can improve the accuracy of discharge measurement in the “Pant Leg” and thereby increase the 

efficiency of water-management administration for both countries. 

The use of ADCP technology proved to be effective within the range of discharges that 

occurred during that 3-day period; however, the test addressed only a relatively small range of 

discharge variations and provided “snapshot” values rather than a continuous record. Additional 

investigation would be needed to indicate whether a permanent installation with a fixed-position 

ADCP system could provide accurate real-time discharge measurements in this channel. ADCP 

measurements over the full yearly operational range of the Power Project would be needed to 

assess whether the differences in discharge measurements by an ADCP and the estimates made by 

NYPA are constant within ranges beyond those measured during this 3-day study. 

Acknowledgments 

Thanks are extended to Thomas Key of the Electric Power Research Institute and to 

Robert Schwabe, Jiankang Zhu, Joseph Meenaghan, James Rankin, and James Ellis of the 

New York Power Authority for all their logistical support at the study site, and Neil Watson and 

Aaron Kennerly of TVGA Consultants, Buffalo, N.Y., for providing general engineering 

information and logistical support for work at the Niagara Power project. 

18
References Cited 

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open-channel discharge: U.S. Geological Survey Water-Supply Paper 2090, 154 p. 

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discharge: U.S. Geological Survey Water-Resources Investigations Report 95–4218, 37 p. 

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Investigations Report 2005–5183, 35 p. 

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Survey Water-Supply Paper 2175, v. 2, 631 p. 

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Profiler: U.S. Geological Survey Open-File Report 01–01, 123 p. 

Simpson, M.R., and Oltmann, R.N., 1992, Discharge measurements using an Acoustic Doppler 

Current Profiler: U.S. Geological Survey Water-Supply Paper 2395, 34 p. 

U.S. Geological Survey, 2003, Release of WinRiver Software version 10.05 for computing 

streamflow from Acoustic Profiler data: Office of Surface Water Technical Memorandum 

2003.04: accessed January 17, 2007, at http://hydroacoustics.usgs.gov/policy/OSW2003-04.pdf 

19
Appendix. Acoustic Doppler Current Profiler transect start and end times and durations, recorded 

channel velocities, flow directions, and total discharges, at New York Power Authority Niagara 

Power Project generation facility, Niagara Falls, N.Y., November 6–8, 2006. 

[ft/s, feet per second; ft3/s, cubic feet per second. Location is shown in fig. 2] 

File Name Start Time End Time 

Transect 

duration 

[minutes] 

Channel 

velocity 

[ft/s] 

Flow 

direction 

[azimuth] 

Total 

discharge 

[ft3/s] 

November 6, 2006 – Measurement Session 1 

Nfalls1106001r.000 14:45:20 14:49:45 4.4 6.17 352.32 88,106 

Nfalls1106002r.000 14:50:23 14:54:57 4.6 6.38 351.64 94,030 

Nfalls1106003r.000 14:55:22 14:59:39 4.3 6.41 352.89 94,448 

Nfalls1106004r.000 14:59:48 15:04:37 4.8 6.48 352.52 90,640 

Nfalls1106B000r.000 15:11:58 15:18:27 6.5 6.92 352.04 91,739 

Nfalls1106B001r.000 15:18:38 15:23:59 5.3 6.25 351.35 87,794 

Nfalls1106B002r.000 15:24:10 15:31:13 7.1 6.67 351.04 85,541 

Nfalls1106B003r.000 15:32:14 15:37:59 5.8 6.24 351.69 87,590 

Nfalls1106C000r.000 15:44:19 15:50:31 6.2 6.33 349.84 89,181 

Nfalls1106C001r.000 15:51:22 15:55:01 3.6 6.37 353.47 89,481 

Nfalls1106C002r.000 15:55:14 15:59:57 4.7 6.36 352.1 85,982 

Nfalls1106C003r.000 16:00:50 16:04:45 3.9 6.71 353.46 91,986 

Session Average 89,700 

November 7, 2006 – Measurement Session 2 

Nfalls1107001r.000 10:17:56 10:28:11 10.2 5.51 352.43 76,973 

Nfalls1107002r.000 10:29:03 10:40:20 11.3 5.64 353.64 77,710 

Nfalls1107003r.000 10:40:51 10:50:35 9.7 6.21 352.75 82,736 

Nfalls1107004r.000 10:50:55 10:59:18 8.4 6.16 352.89 85,112 

Nfalls1107005r.000 10:59:35 11:07:51 8.3 6.03 352.44 84,486 

Nfalls1107006r.000 11:09:32 11:15:50 6.3 6.27 352.29 86,030 

Nfalls1107007r.000 11:16:08 11:23:20 7.2 6.21 352.97 82,971 

Nfalls1107008r.000 11:23:37 11:30:46 7.2 5.81 351.77 79,782 

Nfalls1107009r.000 11:31:07 11:39:55 8.8 5.65 352 87,031 

Nfalls1107010r.000 11:40:16 11:47:37 7.3 6.49 350.24 85,948 

Nfalls1107011r.000 11:47:53 11:55:56 8.1 6.55 350.91 84,790 

Nfalls1107012r.000 11:56:27 12:02:54 6.5 6.52 352.54 89,278 

Session Average 83,600 

20
Appendix. Acoustic Doppler Current Profiler transect start and end times and durations, recorded 

channel velocities, flow directions, and total discharges, at New York Power Authority Niagara 

Power Project generation facility, Niagara Falls, N.Y., November 6–8, 2006.—Continued 

[ft/s, feet per second; ft3/s, cubic feet per second. Location is shown in fig. 2] 

File Name Start Time End Time 

Transect 

duration 

[minutes] 

Channel 

velocity 

[ft/s] 

Flow 

direction 

[azimuth] 

Total 

discharge 

[ft3/s] 

November 7, 2006 – Measurement Session 3 

NFalls1107014r.000 14:25:15 14:29:56 4.7 6.62 353.04 87,099 

NFalls1107015r.000 14:30:33 14:34:48 4.2 7.18 352.02 92,368 

NFalls1107016r.000 14:35:03 14:39:35 4.5 6.98 353.22 92,554 

NFalls1107017r.000 14:40:02 14:44:17 4.2 7.11 352.2 94,079 

NFalls1107018r.000 14:44:38 14:48:48 4.2 6.96 353.31 95,395 

NFalls1107019r.000 14:49:11 14:53:43 4.5 7.02 353.75 92,999 

NFalls1107020r.000 14:54:01 14:58:12 4.2 7.02 353.01 90,622 

NFalls1107022r.000 15:00:42 15:05:14 4.5 7.06 353.43 90,485 

NFalls1107023r.000 15:05:30 15:09:09 3.7 7.03 352.66 88,349 

NFalls1107024r.000 15:10:04 15:14:56 4.9 7.23 353.03 93,045 

NFalls1107025r.000 15:15:47 15:20:01 4.2 6.84 353.05 90,290 

NFalls1107027r.000 15:30:00 15:34:10 4.2 6.56 352.03 87,012 

NFalls1107028r.000 15:34:30 15:38:18 3.8 6.70 352.59 89,693 

NFalls1107029r.000 15:38:32 15:42:24 3.9 6.63 351.85 91,047 

NFalls1107030r.000 15:43:02 15:46:26 3.4 6.63 352.79 89,343 

NFalls1107031r.000 15:46:43 15:50:57 4.2 6.71 352.46 87,882 

NFalls1107032r.000 15:51:20 15:54:50 3.5 6.22 352.21 88,042 

Session Average 90,600 

November 8, 2006 – Measurement Session 4 

NFalls1108001r.000 10:17:12 10:22:13 5.0 6.14 353.71 86,123 

NFalls1108002r.000 10:22:50 10:27:37 4.8 6.25 353.72 88,552 

NFalls1108003r.000 10:27:54 10:32:55 5.0 6.27 352.98 88,929 

NFalls1108005r.000 10:33:55 10:37:59 4.1 6.34 352.8 87,497 

NFalls1108006r.000 10:38:16 10:42:52 4.6 6.52 352.82 89,806 

NFalls1108007r.000 10:43:13 10:47:08 3.9 6.55 353.78 91,535 

NFalls1108008r.000 10:47:27 10:51:38 4.2 6.28 352.75 88,312 

NFalls1108009r.000 10:52:17 10:55:48 3.5 6.07 353.28 85,290 

NFalls1108010r.000 10:56:14 11:00:10 3.9 6.17 351.93 88,014 

NFalls1108011r.000 11:00:51 11:03:48 2.9 6.19 352.57 90,498 

NFalls1108012r.000 11:04:52 11:08:51 4.0 6.16 352.3 87,843 

NFalls1108013r.000 11:09:19 11:12:48 3.5 6.57 352.92 90,024 

Session Average 88,500 

21
For more information concerning the research in this report, contact:

U.S. Geological Survey

New York Water Science Center

30 Brown Rd.

Ithaca, NY 14850

For information requests:

(518) 285-5602

or visit our Web site at:

http://ny.water.usgs.gov
Zajd—Evaluation of Acoustic Doppler Current Profiler to Measure Discharge at New York Power Authority’s Niagara Power Project—OFR 2007–1187