U.S. Department of the Interior

Bureau of Reclamation 

Denver, Colorado April 2009 

Water Resources Technical Publication 

Guidelines for Performing 

Hydraulic Field Evaluations 

at Fish Screening Facilities 

U.S. Department of the Interior

Bureau of Reclamation 

Denver, Colorado April 2009 

Guidelines for Performing 

Hydraulic Field Evaluations 

at Fish Screening Facilities
Acknowledgments 

The funding for this work was supplied by the Bureau of Reclamation Technical 

Service Center’s Manuals and Standards Program and the Bureau of 

Reclamation’s Science and Technology Research Program. 

These guidelines were written primarily by Connie DeMoyer, P.E., Hydraulic 

Engineer, and Tracy Vermeyen, P.E., Hydraulic Engineer, from the Bureau of 

Reclamation’s Hydraulics Laboratory. Review, comments, and guidance were 

provided by Steve Thomas, National Marine Fisheries Service; Warren Frizell, 

Bureau of Reclamation; Brent Mefford, Bureau of Reclamation; and Dan Meier, 

U.S. Fish and Wildlife Service. Technical editing was performed by Teri 

Manross, Bureau of Reclamation. 

Disclaimer 

No warranty is expressed or implied regarding the usefulness or completeness of 

the information contained in this report. References to commercial products do 

not imply endorsement by the Bureau of Reclamation and may not be used for 

advertising or promotional purposes. 

Mission Statements 

The mission of the Department of the Interior is to protect and provide access to 

our Nation's natural and cultural heritage and honor our trust responsibilities to 

Indian tribes and our commitments to island communities. 

The mission of the Bureau of Reclamation is to manage, develop, and protect 

water and related resources in an environmentally and economically sound 

manner in the interest of the American public. 
iii

Abbreviations and Acronyms 

1D one dimensional 

2D two dimensional 

3D three dimensional 

ADC acoustic digital current 

ADCP acoustic Doppler current profiler 

ADFM acoustic Doppler flowmeter 

ADV acoustic Doppler velocimeter 

CDFG California Department of Fish and Game 

EM electromagnetic 

ft ft 

ft/s feet per second 

ft3

/s cubic feet per second 

GCID Glenn-Colusa Irrigation District 

GPS global positioning system 

Hz hertz 

MHz megahertz 

NMFS National Marine Fisheries Service 

Reclamation Bureau of Reclamation

v

Table of Contents 

Page 

Abbreviations and Acronyms ................................................................................iii 

Table of Contents.................................................................................................... v 

Figures.................................................................................................................... vi 

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

Overview of Hydraulic Evaluations at Fish Screening Facilities ........................... 2 

Fish Protection Criteria........................................................................................... 7 

Positive Barrier Screens...................................................................................... 7 

Fish Screen Velocity Magnitudes ................................................................. 10 

Fish Screen Velocity Uniformity.................................................................. 10 

Screen Submergence..................................................................................... 10 

Fish Bypass System Velocities ..................................................................... 11 

Flow Continuity ............................................................................................ 11 

Behavioral Barriers ........................................................................................... 11 

Instrumentation ..................................................................................................... 12 

Instruments for Near-Field Screen Measurements ........................................... 12 

Acoustic Doppler Velocimeter ..................................................................... 12 

Electromagnetic Velocimeter........................................................................ 14 

Instruments for Fish Bypass System Measurements ........................................ 14 

Acoustic Doppler Velocimeter ..................................................................... 15 

Other Velocity Meters................................................................................... 15 

Acoustic Doppler Flowmeter........................................................................ 15 

Ultrasonic Noncontact Flowmeter ................................................................ 16 

Support Instrumentation.................................................................................... 17 

Acoustic Doppler Current Profilers .............................................................. 17 

Mounting System for Instruments .................................................................... 19 

Types of Hydraulic Screen Evaluations................................................................ 20 

Postconstruction Field Evaluations................................................................... 20 

Long-Term Field Monitoring Programs ........................................................... 20 

Field Evaluation Case Studies .............................................................................. 21 

Glenn-Colusa Irrigation District (GCID) Diversion......................................... 21 

Roza Fish Screens Facility................................................................................ 24 

Red Bluff Research Pumping Plant .................................................................. 27 

Submerged Cylindrical Screens........................................................................ 29 

Tracy Fish Collection Facility .......................................................................... 31 

References............................................................................................................. 35 
vi 

Figures 

Page 

1 Government Highline Canal in-canal V-screen near Grand Junction, 

Colorado. This construction photo shows the wedge-wire flat plate 

screen panels (right), vertical baffles (left), and fish bypass intake 

(center)................................................................................................. 3 

2 Flat plate screens installed at Wilkins Slough Pumping Plant on the 

Sacramento River (Reclamation District No. 108). On-river fish 

screens are common for large diversions............................................. 3 

3 Multiple traveling screens at Roza Fish Screens Facility near Yakima, 

Washington.......................................................................................... 4 

4 Inclined screens at Savage Rapids Diversion near Grants Pass, Oregon. 4 

5 Coanda screen at Lake John near Walden, Colorado. ......................... 5 

6 Rotating drum screens at Roza Fish Screens Facility near Yakima, 

Washington.......................................................................................... 5 

7 Retractable submerged cylindrical screen on Sacramento River 

near Grimes, California. ...................................................................... 5 

8 Cone screen installed by Intake Screens, Inc. Cone screens are 

typically used in shallow estuaries or tidally influenced areas............ 6 

9 Louver line at Tracy Fish Collection Facility near Tracy, 

California. ............................................................................................ 6 

10 Plan view of an in-canal fish screening structure ................................ 9 

11 SonTek/YSI 10-MHz ADV probe and splash proof signal 

processing housing photo. ................................................................... 13 

12 Nortek Vector velocimeter 6-MHz probe and submersible 

signal processing housing.................................................................... 13 

13 Marsh-McBirney Flo-Mate 2000 portable electromagnetic 

sensor, cable, and splash proof electronics housing ............................ 14 

14 OTT acoustic digital current meter (photo courtesy of OTT). ............ 15 

15 Teledyne ISCO 1.23-MHz ADFM Pro20............................................ 16 

16 SonTek/YSI 3-MHz Argonaut-SW ..................................................... 16 

17 Teledyne/RDI V-ADCP 2.4-MHz acoustic Doppler flowmeter ......... 16 

18 Controlotron portable clamp-on flowmeter Model 1010WP............... 16 

19 OTT QLiner acoustic Doppler profiler................................................ 17 

20 SonTek/YSI RiverCat acoustic Doppler profiling system................... 18
vii

Figures 

Page 

21 Linkquest’s line of ACPs (photo courtesy of Linkquest, Inc.)............ 18 

22 A typical setup using a Teledyne/RDI Workhorse Rio Grande 

ADCP with Trimble GPS to collect bathymetric survey data. ............ 18 

23. GCID’s Hamilton City diversion facilities located in an oxbow 

along the Sacramento River................................................................. 222 

24 Magnetic ADV mount used at GCID. ................................................. 23 

25 Cross section of velocity magnitudes collected in the GCID 

pumping plant approach channel......................................................... 24 

26 Rotating drum screens in one bay of Roza Fish Screens Facility........ 25 

27 A cantilevered steel mount with a horizontally adjustable 

arm was used to measure velocities close to the screen face 

near the surface (as shown) and under the curvature of the screen. .... 25 

28 Schematic of measurement locations at a distance of 3 inches 

from the screen face and along the vertical projection of 

the screen ............................................................................................. 26 

29 Overview of Red Bluff Research Pumping Plant................................ 28 

30 Flat plate V-screen with a terminal fish bypass................................... 28 

31 Adjustable baffles located behind fish screen panels. ......................... 29 

32 Plan view schematic of the Tracy Fish Collection Facility near Tracy, 

California. ............................................................................................ 31 

33 Mounting an ADV to the louver line................................................... 32 

34 Positioning the ADP in front of the bypass intake. ............................. 32

1

Introduction 

The Bureau of Reclamation (Reclamation) must comply with Federal and State 

fisheries criteria at water diversion structures and their components. Reclamation 

currently conducts field measurement evaluations with specialized 

instrumentation at diversion facilities used for irrigation, power generation, and 

water supply. Various structures such as fish screens, fish bypasses, screened 

pump intakes, and louver systems must comply with Federal and State fisheries 

criteria in order to maintain uninterrupted operations. 

Since diversion structures have site-specific geometry, components, and 

operational goals, and fisheries criteria vary by species, life stage, season, and 

region, it is not possible to recommend one standard method for conducting 

hydraulic evaluations at all field sites. The intent of these guidelines is to offer 

general field methodologies and instrumentation that can be applied to field 

evaluations. Keeping in mind that each site requires unique consideration, these 

guidelines will be a resource for field personnel in planning an efficient testing 

program with appropriate instrumentation. 

Reclamation published Fish Protection at Water Diversions (Bureau of 

Reclamation, 2006) to provide design guidance for fish protection at small dams 

and water diversion structures. This technical publication will be used internally 

by Reclamation and as a technology transfer to other agencies and the public. As 

a supplement to Fish Protection at Water Diversions, these guidelines provide 

information on conducting hydraulic field evaluations at water diversion 

structures. 

These guidelines address field evaluations at diversion structures with fish 

screens, including an overview of various types of positive barrier and behavioral 

fish screens that are commonly installed at diversion structures. The regulatory 

agencies that typically develop screening criteria are identified. Information is 

provided on how to obtain current criteria for the region where hydraulic 

evaluations are being conducted. 

Important parameters needed for hydraulic evaluations will be summarized. The 

guidelines identify typical measurement locations that are considered critical to 

fish passage and survival by fisheries agencies and acceptable, practical methods 

that can be used to evaluate these critical locations. The guidelines also identify 

specific areas where the best methodology is unclear. Several field instruments 

are discussed and compared. Postconstruction evaluations for baffle adjustment 

and performance validation, as well as long-term monitoring programs, are 

discussed. The guidelines conclude with case studies of several hydraulic fish 

screen evaluations. These case studies describe some of the challenges that a 

researcher may encounter during field evaluations. 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

2 

Overview of Hydraulic Evaluations at 

Fish Screening Facilities 

Fish protection structures may be installed at water diversions to prevent or 

reduce fish entrainment into the diversion. The objective of water resources 

agencies and organizations installing fish protection structures is to abide by State 

and Federal laws to preserve endangered species while continuing to meet current 

water deliveries and allowing for future water development. Hydraulic 

evaluations are needed to ensure that the hydraulic performance of the structure 

optimizes fish exclusion efficiencies and satisfies all applicable State and Federal 

fisheries criteria. 

The primary component of a fish protection structure is a positive barrier fish 

screen or behavioral barrier. Reclamation’s Fish Protection at Water Diversions

manual contains a comprehensive discussion of fish protection alternatives, 

including detailed descriptions, advantages and disadvantages, and examples of 

installation locations (Bureau of Reclamation, 2006). 

Positive barrier screens create a physical boundary to fish passage. Off-river 

barrier screens contain a fish bypass component to return fish safely back to the 

river. Positive barrier screens are highly effective at reducing fish entrainment, 

but hydraulic conditions must be monitored to prevent fish injury or mortality 

from impingement on the screens or delay in migratory passage. Since positive 

barrier screens are highly susceptible to debris fouling and sediment deposition, 

cleaning mechanisms and sediment control devices are typically included in the 

design. These types of devices can affect hydraulic field evaluations by hindering 

access to the screens or altering flow patterns near the screens. 

Positive barrier screens include flat plate screens (figures 1 and 2), traveling 

screens (figure 3), bottom screens such as inclined and horizontal flat plate 

screens (figure 4), Coanda screens (figure 5), drum screens (figure 6), submerged 

cylindrical screens (figure 7), cone screens (figure 8), and closed conduit (Eicher 

and modular inclined screen [MIS]) screens. 

Behavioral barriers produce a stimulus that elicits a fish response to avoid 

entrainment. As a structural guidance device, vertical louvers (figure 9) are 

intended to achieve fish exclusion by generating disturbances in the flow field that 

fish respond to and avoid. Fish maintain a distance off the louver face, while the 

sweeping flow is intended to guide fish along the louver line and into the 

bypasses. Alternative behavioral technologies include light and acoustic devices, 

electric fields, air bubble curtains, hanging chains, and water jet curtains. 

Although fish exclusion efficiencies can be much lower than positive barrier 

screens, behavior barriers are generally less expensive to install and easier to 

maintain. They may be a viable option at sites where 100-percent exclusion
Overview of Hydraulic Evaluations at Fish Screening Facilities 

3

is not required or where installation of a positive barrier is difficult or 

inappropriate due to site-specific issues. 

Figure 1. Government Highline Canal in-canal V-screen near Grand 

Junction, Colorado. This construction photo shows the wedge-wire 

flat plate screen panels (right), vertical baffles (left), and fish bypass 

intake (center). 

Figure 2. Flat plate screens installed at Wilkins Slough Pumping 

Plant on the Sacramento River (Reclamation District No. 108). Onriver fish screens are common for large diversions. 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

4 

Figure 3. Multiple traveling screens at Roza Fish Screens Facility 

near Yakima, Washington. 

 

Figure 4. Inclined screens at Savage Rapids Diversion near Grants 

Pass, Oregon. 
Overview of Hydraulic Evaluations at Fish Screening Facilities 

5

Figure 5. Coanda screen at Lake John near Walden, Colorado. 

Figure 6. Rotating drum screens at 

Roza Fish Screens Facility near 

Yakima, Washington. 

Figure 7. Retractable submerged 

cylindrical screen on Sacramento 

River near Grimes, California. 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

6 

Figure 8. Cone screen installed by Intake Screens, Inc. Cone screens are 

typically used in shallow estuaries or tidally influenced areas (photo courtesy 

of Intake Screens, Inc.) 

. 

Figure 9 . Louver line at Tracy Fish Collection Facility near Tracy, California. 
Fish Protection Criteria 

7

In addition to a fish barrier, several other components may be present at a water 

diversion, including debris booms, trashracks, fish bypass systems, cleaning 

mechanisms, sediment control devices, and pumping or dewatering facilities. 

Hydraulic field evaluations may be required at any or all of the fish protection 

components at a diversion facility. 

At fish protection structures, postconstruction field evaluations may be required to 

validate design performance or to adjust flow baffles or weirs to obtain effective 

performance. Hydraulic evaluations may be requested to identify optimal 

operational conditions during critical fish protection periods. Long-term 

monitoring tests are used to ensure proper performance and to address cleaning or 

maintenance concerns. 

Field evaluations are generally conducted by qualified personnel from the agency 

or organization that owns the diversion structure. If specialized expertise or local 

employment is desired, evaluations may be performed by private consulting 

companies, irrigation districts, or other State or Federal agencies. 

Fish Protection Criteria 

Positive Barrier Screens 

Federal and State agencies develop, update, and enforce fish screening criteria to 

protect fishery resources at water diversions. Fish Protection at Water Diversions

gives a synopsis of fish protection legislation and lists the Federal and State 

agencies that have authority over, or a vested interest in, fishery resources in the 

United States (Bureau of Reclamation, 2006). 

Federal governance of fish screening criteria is dictated by the Endangered 

Species Act, Federal Power Act, and Fish and Wildlife Coordination Act. The 

National Marine Fisheries Service (NMFS) prepares fish protection criteria for 

anadromous fish (species that migrate up rivers from the sea to spawn in fresh 

water) listed under the Endangered Species Act. The U.S. Fish and Wildlife 

Service applies fish protection requirements for endangered nonanadromous 

species on a project-specific basis. State fish and game agencies enforce and, in 

some cases, design local criteria governing the protection of endangered and 

nonendangered species. If State or local agencies have more stringent screening 

criteria, the more conservative criteria are generally followed. See Attachment A 

of Fish Protection at Water Diversions for examples of Federal and State fish 

screening criteria. 

When a field evaluation is requested, the researcher must identify the fish 

screening criteria that apply to the water diversion. Pump intake screening 

criteria may be described separately from general fish screening criteria. There is 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

8 

not one universal set of fisheries criteria. Fisheries criteria vary by species, life 

stage, region, and season. Water resource managers and resource agency staff 

with working knowledge of the fish protection structure are often the best 

resource for obtaining this information. If there is a discrepancy over which 

criteria to use or whether updated criteria are available, the field researcher can 

obtain updated criteria from the regional resource agency that maintains screening 

criteria for fish species that are affected by the water diversion. It is possible that 

certain elements of the criteria may be waived due to site constraints or for 

screens constructed prior to enactment of criteria. 

Since there is a broad range of screening criteria, the specific details of criteria 

will not be discussed. However, several important parameters and critical 

measurement locations are common to most hydraulic field evaluations. 

Important definitions related to hydraulic field evaluations include: 

Channel velocity: Velocity of the flow approaching the fish screen or louver, 

consisting of the approach and sweeping velocity components (depicted as Vc 

in figure 10). 

Approach velocity: Velocity vector component perpendicular to, and in front 

of, the screen face (depicted as Va in figure 10). 

Sweeping velocity: Velocity vector component parallel and adjacent to the 

screen face (depicted as Vs in figure 10). For pump intake screens, the 

sweeping velocity is measured with the pump turned off (National Marine 

Fisheries Service, 1996). 

Baffle system: Perforated plate, flow control louvers or vanes, stoplogs, or 

other flow restriction or resistance element installed behind fish screens (or 

inside the screen for cylindrical screens). When adjusted properly, the baffles 

generate localized head loss to produce a more uniform velocity distribution 

near the screen face. 

Bypass flow: Flow rate necessary to effectively attract fish into the bypass 

entrance and through the bypass system. 

Bypass ratio: Ratio of the water velocity entering the bypass to the water 

velocity in the main channel 

Effective screen area: Total submerged screen area, excluding structural 

members. For rotating drum screens, it is the projected area onto a vertical 

plane. 

Fish bypass system: Component of a downstream passage facility that 

transports fish from the diverted water back into the original body of water, 

usually consisting of a bypass entrance, a bypass conduit, and a bypass outfall. 
Fish Protection Criteria 

9

Impingement: Prolonged physical contact of fish with a structure due to its 

inability to swim against the approach velocity. 

Pump intake screen: Screening device attached directly to a pressurized 

diversion intake pipe. Typically, active pump intake screens are equipped 

with a cleaning mechanism, while passive pump intake screens do not have 

a cleaning mechanism. 

Figure 10. Plan view of an in-canal fish screening structure. 

The channel velocity (Vc) approaches the screen face. The 

approach velocity component (Va) is perpendicular to the 

screen face, and the sweeping velocity component (Vs) is 

parallel to the screen face. 

During a hydraulic field evaluation of a fish screening facility, velocity 

measurements are typically made near the screen face, at the bypass entrance, and 

inside the bypass channel or conduit. Water depths in the forebay, at the upstream 

face of the screen, and in the bypass may need to be measured. 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

10 

The following critical measurement locations and generalized criteria are 

commonly identified for hydraulic field evaluations: 

Fish Screen Velocity Magnitudes 

• Approach velocity must be less than a specified allowable value at a 

location, typically 3 inches perpendicular to, and in front of, the screen 

face (deviations from the 3-inch requirement may be necessary when the 

total screen surface is not readily available, as for cylindrical-shaped 

screens). 

• Sweeping velocity must be greater than approach velocity. An optimal 

sweeping velocity or sweep-to-approach velocity ratio may be specified. 

• Sweeping velocity shall not decrease in the downstream direction along 

the length of the screen face or in the bypass channel. 

Fish Screen Velocity Uniformity 

• A uniform velocity distribution should be maintained over the screen 

surface to minimize approach velocities. (Note: Adjustable porosity 

control or baffles on the downstream side of screens and/or flow training 

walls may be installed to improve uniformity.) 

• Approach and sweep velocities should be measured at a specified distance 

from the screen face (typically 3 inches). Multiple sampling points are 

collected over the screen face, with each point representing the flow 

conditions over a particular percentage of the open screen area. 

• Criteria may or may not define “uniformity.” Specific criteria may state 

that uniform approach conditions are achieved when no individual 

approach velocity measurement exceeds the allowable criteria value by a 

specified percentage. If uniformity is undefined, fishery resource agency 

staff may have general guidance for acceptable distributions at the site. 

Screen Submergence 

• A minimum effective screen area must be submerged so that the allowable 

approach velocity can be achieved. For rotating drum screens, the design 

submergence will be defined as a percentage of the drum diameter. For 

cylindrical pump intake screens, the depth of submergence will be defined 

as a specified screen radius below the minimum water surface. 
Fish Protection Criteria 

11

Fish Bypass System Velocities 

• Criteria may specify that the minimum bypass entrance flow velocity be 

greater than the maximum velocity upstream of the bypass entrance by a 

specified percentage. 

• A maximum increase rate per foot of travel (acceleration) may be required 

between the screens and the bypass system. 

• A design velocity range for the bypass conduit may be specified. 

• A maximum impact velocity from the bypass outfall may be specified.

Flow Continuity 

• Flow continuity is a comparison of the calculated water diversion rate 

using the approach velocities and the submerged screen area from the field 

evaluation to the measured water diversion rate from facility flow 

measurement instrumentation. 

• If the calculated discharge values are significantly different from the 

measured values, the approach velocities may not be fully describing the 

flow conditions along the entire screen or may not have accounted for hot 

and/or cold spots. If continuity is not conserved, it is possible that the 

instrument mounting technique may have interfered with velocity 

collection or the experimental setup was in error. 

Behavioral Barriers 

Behavioral barriers are generally not accepted by regulatory agencies since 

exclusion rates tend to be lower than conventional positive barrier screens. Fish 

species and life stage, along with site-specific hydraulic and environmental 

conditions, often cause the effectiveness of behavioral barriers to vary. Specific 

criteria for behavioral barriers are not published; however, some guidance on the 

experimental process for researching experimental fish guidance devices can be 

found in NMFS literature (National Marine Fisheries Service, 1994). When 

behavioral barriers are employed at a site, regulatory agencies will likely require 

site-specific field studies to show that fish exclusion performance is acceptable. 

Postconstruction or periodic efficiency evaluations at louver systems involve 

many of the same critical measurement locations as fish screening systems. 

Effectiveness of louver systems depends on maintaining uniform sweeping flow 

across the louver face and guiding fish efficiently into the bypasses. Passage 

delays throughout the system should be minimized. Fish should not be exposed to 

the louver line for more than 60 seconds without access to a bypass to minimize 

loss through the louvers. Fish should be accelerated into the fish bypass. The 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

12 

bypass ratio, defined as the velocity in the bypass divided by the channel velocity 

in front of the bypass, should always be greater than 1.0 to effectively transport 

fish into and through the bypass. 

The effectiveness of acoustic and light barriers, electric fields, air bubble curtains, 

and other behavioral exclusion methods are analyzed primarily using fish release 

and capture tests. These tests quantify barrier efficiency under a wide range of 

environmental conditions such as day and night, tidal cycles, and flow rates. 

Hydraulic evaluations typically include measuring velocities and mapping flow 

fields near to the barrier because hydraulic conditions can greatly contribute to the 

overall effectiveness of these barriers. 

Instrumentation 

Hydraulic field data are collected with a combination of portable instrumentation 

and permanent facility equipment. Several types of portable instruments can be 

used to measure velocities and flow rates at fish screening facilities. Instrument 

capabilities, performance specifications, costs, and availability may dictate which 

type of equipment is chosen. Selection of instrumentation may be dependent on 

site-specific factors such as site location and geometry, water quality, support 

structure interference (cleaning arms, dividing piers), and difficulties related to 

mounting and retrieving the instruments. 

To assist in selecting the most appropriate field instrumentation for a hydraulic 

study, a description of various available technologies is provided, along with 

some advantages and disadvantages of using the instrument for the specified 

application. There are many high-quality instruments available in each 

instrumentation category. Specific proprietary products and materials are only 

mentioned to provide examples of the instruments but this should not in any way 

be construed as an endorsement by Reclamation. The appropriate instrumentation 

and mounting technique must be determined by the practitioner. 

Instruments for Near-Field Screen Measurements 

Acoustic Doppler Velocimeter 

Acoustic Doppler velocimeters (ADV) utilize the Doppler principle to measure 

three-dimensional (3D) velocity vectors in a small remote sampling volume. The 

ADV emits sound pulses (pings) at a specific frequency. At a fixed distance 

from the probe, the signal reflects off of particles present in the water, providing 

a precise instantaneous reading at a “point” (i.e., sample volume of about 

0.01 cubic inches). The frequency shift of the returning sound wave 

increases or decreases, depending on whether the water is moving toward or 
Instrumentation 

13

away from the receivers. The difference between the emitted and received 

frequency is used to calculate the water velocity. 

Typically, ADV probes are configured as “down-looking” or “side-looking,” 

describing the location of the sample volume with respect to the probe axis, and 

can collect two-dimensional (2D) or 3D velocity data. ADVs are effective for 

measuring near-screen velocities because they can measure close to boundaries. 

ADVs can fit into areas with minimal lateral clearance, but they cannot fit into 

areas with minimal vertical clearance, such as underneath the curvature of a drum 

screen, due to the configuration of the signal conditioning module. Particles in 

the water act as scatterers to provide adequate return signal strength and signal-tonoise ratio. If the ADV does not have a strong signal in clean water applications, 

the water may need to be seeded with scattering material if possible. ADVs are 

not able to collect data in water with heavy air entrainment because bubbles 

attenuate the acoustic energy. 

It is good practice to check the factory calibration of an ADV before each use. 

However, an ADV does not require periodic calibration unless the physical 

characteristics of the probe are changed (e.g., a receiver arm is bent). If an 

ADV probe is damaged during transport or use, factory repair and recalibration 

are required. 

An example of a commercially available acoustic Doppler velocimeter is the 

SonTek/YSI ADV (figure 11). The 10-megahertz (MHz) ADV can acquire data 

at sampling rates up to 25 hertz (Hz), allowing for the measurement of turbulence. 

With no zero offset, the ADV performs at low flows and is bidirectional. The 

6-MHz Nortek Vector velocimeter can collect data at a rate as high as 64 Hz 

(figure 12). 

Figure 11. SonTek/YSI 10-MHz ADV 

probe and splash proof signal 

processing housing photo (courtesy 

of SonTek/YSI). 

Figure 12. Nortek Vector 

velocimeter 6-MHz probe and 

submersible signal processing 

housing (photo courtesy of Nortek). 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

14 

Electromagnetic Velocimeter 

Electromagnetic (EM) instruments use Faraday’s Law to measure the velocity of 

a conductive fluid. Water is a conductor due to the presence of trace amounts of 

ions from dissolved minerals. Faraday’s Law states that a conductor passing 

through a magnetic field produces a voltage that is directly proportional to the 

relative velocity of the conductor. EM velocimeters provide a magnetic field, and 

electrode sensors on the probe surface measure the voltage induced by flow 

moving through the magnetic field. 

For screen measurements, a 2D spherical or a one-dimensional (1D) bulb-shaped 

probe are normally used. When oriented properly, a two-dimensional probe 

simultaneously measures localized approach and sweeping velocities at a sample 

rate of up to 1 Hz. Since bulb or spherical shaped probes have electrodes on the 

side(s) of the sensor, the sampling volume is spherical in shape with a diameter of 

approximately 5 inches. The average fluid velocity is measured over the sample 

volume. If only 1D probes are available, a pair of probes must be mounted 

together to measure both approach and sweeping velocities. 

EM velocimeters can fit into small 

measurement areas, which may be 

useful for large diameter drum 

screen and cylindrical screen 

evaluations. The calibration of 

EM meters must be checked before 

each use. Because ferrous metal 

screen materials interact with the 

magnetic field, velocity 

measurements must be taken at 

a minimum distance of 3 inches 

from the screen. One specific 

model of a 1D EM meter is the 

Marsh-McBirney Flo-Mate 2000 

(figure 13). 

Instruments for Fish Bypass System Measurements 

In addition to point velocity measurements near the fish screen, hydraulic screen 

evaluations also may include measurement of water velocities entering the fish 

bypass and flow rates through the bypass pipe. If onsite water measurement weirs 

or permanent flowmeters are installed, they can be used to measure bypass rates. 

Otherwise, portable instrumentation must be used. Some examples of portable 

instruments are discussed below. 

Figure 13. Marsh-McBirney Flo-Mate 

2000 portable electromagnetic sensor, 

cable, and splash proof electronics 

housing (photo courtesy of MarshMcBirney, Inc). 
Instrumentation 

15

Acoustic Doppler Velocimeter 

An ADV (discussed above) can be used to measure point velocities in or near the 

fish bypass system. These measurements may be required to determine if the 

flow is accelerating along the screen and into the bypass. The rate at which flow 

is accelerating can be measured with successive readings. 

If a discharge measurement is required and permanent flowmeters are not 

available, the flow rate can be estimated using stream gauging techniques with an 

ADV or propeller meter (Bureau of Reclamation, 2001). For water depths greater 

than 2 ft, point velocities should be measured at 0.2 and 0.8 of the water depth 

from the surface in the streamwise direction, and the average of these values 

should be used to calculate the flow rate. For water depths less than 2 ft, a point 

velocity measurement at 0.6 of the water depth from the surface in the streamwise 

direction can be used to calculate the flow rate. 

Other Velocity Meters 

The OTT company has recently developed an acoustic digital current (ADC) 

meter, which includes depth measurement with a pressure sensor and temperature 

measurement. This acoustic instrument uses the cross correlation method to 

calculate water velocity. The sampling volume is located about 4 inches from the 

probe face (figure 14). 

Propeller meters are another option for measuring 

1D point velocities in or near the fish bypass system. 

Care must be taken to ensure that the calibration is 

accurate and that the meter is oriented properly. 

Acoustic Doppler Flowmeter 

For discharge measurements, acoustic Doppler 

flowmeters (ADFM)1

 are typically mounted on the 

bottom of a channel or pipe for an “upward looking” 

measurement. Water velocity is measured by the 

Doppler principle via two, angled acoustic beams. 

Water depth is gauged by an uplooking acoustic depth 

sensor. The discharge is computed over the flow 

measurement area using the vertically integrated 

velocity. If the bypass channel is narrow and the water 

is deep, the acoustic signals may encounter boundary 

interference and cannot be used. Three examples of 

acoustic Doppler profiling flowmeters include the 

Teledyne ISCO 1.23-MHz ADFM Pro20 (figure 15), 

 1

 The acoustic Doppler flowmeter may also be referred to as an acoustic Doppler current profiler 

(ADCP). 

Figure 14. OTT 

acoustic digital 

current meter 

(photo courtesy of 

OTT). 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

16 

the SonTek/YSI 3-MHz Argonaut-SW (figure 16), and the Teledyne/RDI 2.4-

MHz V-acoustic Doppler current profiler (ADCP) (figure 17). 

Figure 15. Teledyne ISCO 1.23-MHz 

ADFM Pro20 (photo courtesy of 

Teledyne ISCO, Inc). 

Figure 16. SonTek/YSI 3-MHz ArgonautSW (photo courtesy of SonTek/YSI). 

Ultrasonic Noncontact Flowmeter 

To measure the flow rate of a full-flowing closed conduit, noncontact ultrasonic 

meters can be clamped to a pipe. The flow measurement is based on the principle 

that sound waves in the fluid travel faster in the downstream direction than 

traveling in the upstream direction. The difference in transit times of the 

ultrasonic signals is a measure of the average fluid velocity. There are many 

manufacturers of ultrasonic, noncontact flowmeters. The Controlotron portable 

clamp-on flowmeter (shown in figure 18) is one example. 

Figure 17. Teledyne/RDI V-ADCP 2.4-MHz 

acoustic Doppler flowmeter (photo courtesy 

of Teledyne/RDI, Inc). 

Figure 18. Controlotron 

portable clamp-on flowmeter 

Model 1010WP (photo courtesy 

of Controlotron). 
Instrumentation 

17

Support Instrumentation 

Acoustic Doppler Current Profilers 

Acoustic current profilers (ACP) also utilize the Doppler frequency shift principle 

to measure two- or three-dimensional velocity profiles in a user-specified number 

of depth cells. The acoustic frequency of the transceivers determines the range of 

the instrument and the depth size for the profile. 

ACP instruments measure velocity over a large sampling volume (defined by the 

transceiver configuration) as opposed to point or localized velocity measured 

using an ADV or EM velocimeter. Although an ACP is not suited to measure 

near-screen velocities, it can be successfully used as a support instrument to 

examine approach conditions at various cross sections near the screening facility 

(Vermeyen and DeMoyer, 2002). Cross sections can also be taken along the 

length of the screens, in front or back, to identify hot spots on the screens. 

Examination of backscatter intensity data can provide qualitative information 

about suspended sediment concentrations and areas of local scour. 

Instruments such as the OTT QLiner measure velocity profile data in a single 

plane (either vertical or horizontal, depending on the instrument orientation), 

requiring input of channel cross section geometry for a discharge measurement 

(figure 19). Instruments such as the SonTek/YSI RiverCat calculate discharge by 

making alternating measurements of channel cross sectional area using bottom 

tracking techniques and velocity profiles to define the mean vertical velocity 

(figure 20). Teledyne/RDI offers a similar system called the Workhorse Rio 

Grande ADCP. Linkquest, Inc., has also developed a line of ACPs (figure 21). 

Figure 19. OTT QLiner acoustic Doppler profiler (photo courtesy of 

OTT). 

ACPs are capable of measuring depth for each acoustic beam. As a result, ACPs 

can be used as multi-beam depth sounders along with integrated global 

positioning system (GPS) data for local bathymetric surveys (figure 22). 

Bathymetric data are useful for documenting changes in the approach channel 

geometry due to aggradation, degradation, or dredging. 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

18 

Figure 20. SonTek/YSI RiverCat acoustic Doppler profiling 

system (photo courtesy of SonTek/YSI). 

Figure 22. A typical setup using a Teledyne/RDI Workhorse 

Rio Grande ADCP with Trimble GPS to collect bathymetric 

survey data. 

Figure 21. Linkquest’s line of ACPs 

(photo courtesy of Linkquest, Inc.) 
Instrumentation 

19

Mounting System for Instruments 

Mounting instruments in and around structures is always a site-specific challenge. 

Devising a workable mounting system for the instrument can take a great deal of 

time and effort, but it is a worthwhile investment in order to improve the 

efficiency and accuracy of data collection. 

For fish screen measurements, portable instrumentation must be mounted close to 

the screen face to obtain velocity data. Probe orientation is critical when 

measuring directional flow. If the 2D or 3D probe is even slightly misaligned, the 

measured approach velocity may incorporate part of the sweeping flow, 

producing significant inaccuracies in the data. Some data processing software 

include a way to account for probe misalignment if a systematic problem is 

identified after data have been collected. Reclamation has developed a Windowsbased viewing and postprocessing utility for ADV files called WinADV 

(Wahl, 2009). WinADV provides an integrated environment for reviewing and 

processing data collected using SonTek and Nortek acoustic Doppler 

velocimeters. 

Velocimeters should be clamped onto a sturdy support structure that minimizes 

instrument movement and vibration. The most accurate way to position the 

instrument is to reference it directly off of the screen for each measurement. If a 

long cantilevered mount is necessary, the mount must be rigid so it does not 

deflect or vibrate in fast moving water. If movement is a concern, a stronger 

support should be used or the mount should incorporate intermediate supports 

wherever possible. 

The mount should not block or disrupt the flow field around the instrument. The 

mounting system must have a way to determine the lateral and vertical position of 

the instrument. It is most efficient if the instrument can be moved between 

measurement locations quickly and accurately. In most cases, accurate point 

velocity measurements cannot be made off of a boat because boat movement is 

incorporated into the measured velocity. If a floating platform must be used to 

access the site, it should be securely anchored to minimize motion. 

Velocity and discharge measurements in fish bypass channels may require 

affixing an instrument to the bottom, or near the bottom, of the bypass channel. If 

the bypass cannot be fully dewatered, the instrument should be carefully secured 

to the channel bottom or sidewalls in the wet. The location and orientation of the 

instrument must be known to get accurate results. A heavy weight or plate can 

sometimes be used to fix the position of the instrument. If interference from 

sidewalls or other structures cannot be avoided, a point velocity meter may be 

required. 

Acoustic Doppler profilers or current meters are often mounted off of boats, 

bridges, or rope lines to collect supporting hydraulic data. The deployment 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

20 

mechanism depends on the channel geometry, water depth and velocity, transect 

location, and other site-specific factors. Orientation of current meters is an 

important consideration because the transducer must be aligned parallel to the 

channel centerline or perpendicular to a tagline. Compasses are often integrated 

into acoustic Doppler instruments to allow data collection in earth coordinates. If 

so, a compass calibration is required to compensate for local magnetic fields. 

Types of Hydraulic Screen Evaluations 

Postconstruction Field Evaluations 

The purpose of postconstruction hydraulic evaluations is to validate design 

performance, refine hydraulic conditions, and document facility effectiveness. 

Hydraulic tests may include velocity measurements along the screen face, at the 

bypass entrance and exit, and in the bypass channel or conduit to determine if fish 

will be guided effectively through the system. 

Before conducting a postconstruction evaluation, it is important to determine what 

flow conditions should be evaluated. Depending on the facility, the appropriate 

time period may be at low water depth, normal or peak operations, or a critical 

time period such as during smolt passage. Hydraulic conditions and operational 

settings such as diversion and bypass flow rates, water depths, screen 

submergence, and the weir and baffle settings should be recorded during field 

evaluations. 

For facilities with flow control baffles downstream of the screens, hydraulic 

testing is necessary to properly adjust the baffles to achieve near-uniform 

approach velocities. A trial-and-error process is required to adjust multiple sets of 

flow control louvers, vertical vanes, perforated plates, or flashboards behind each 

screen. Several comparable rounds of velocity data will likely need to be 

collected. Setting baffles for in-canal screening systems tends to be more 

straightforward than adjusting baffles for in-river applications where variable 

hydraulic conditions and dynamic flow patterns add complexity to the system. 

Hydraulic evaluations may also be requested to identify optimal operational 

conditions during critical fish protection periods or to adjust bypass weirs for 

effective performance. 

Long-Term Field Monitoring Programs 

Long-term monitoring tests are used to ensure proper facility performance and to 

identify screen cleaning or maintenance concerns. Periodic hydraulic evaluations 

may be requested to measure approach and sweeping velocities across the screen 
Field Evaluation Case Studies 

21

face to verify screen and baffle performance. Diversion rates can be calculated 

from measured approach velocity values and compared with measured diversion 

rates. 

Structural changes, such as installation of new baffles or cleaning devices, and 

operational changes, due to altered flow rates or criteria requirements, may 

require special hydraulic evaluations. Hydraulic evaluations may also help to 

identify underwater screen damage, debris accumulation, sedimentation, or 

problems with permanent instrumentation. 

Field Evaluation Case Studies 

Glenn-Colusa Irrigation District (GCID) Diversion 

Facility type: In-river flat plate screens 

Challenges: Instrument mounting due to high sweeping velocities, defining 

velocity uniformity for a large facility, data repeatability with dynamic flow 

conditions 

The GCID pump station is located in north-central California, about 100 miles 

north of Sacramento. The diversion facility is located on an oxbow of the 

Sacramento River (figure 23). Up to 3,000 cubic feet per second (ft3/s) of 

Sacramento River water is pumped into GCID’s canal after passing through the 

fish screens. A portion of the water bypasses the screen and flows back into the 

river at the downstream end of the oxbow. 

To protect fish from entrainment in the main irrigation canal, long flat plate 

screens with three fish bypasses were installed at the pump station in 2000 in 

partnership with Reclamation. The U.S. Army Corps of Engineers constructed a 

gradient restoration facility on the main stem of the Sacramento River to stabilize 

the river channel, promote upstream and downstream fish passage, and maintain 

adequate water surface elevations and flow rates for safe fish passage and 

effective screening. More information on GCID’s Fish Screen Project can be 

found on their Web site (GCID, 2009). 

Since construction, many hydraulic evaluations have been conducted by 

CH2M HILL, GCID, NMFS, and Reclamation to adjust the baffle system, 

document screen performance and compliance, and monitor intake and bypass 

channels. Several site-specific issues have made data collection difficult at the 

GCID fish screens. It is important to design a monitoring program after 

site-specific issues are identified, so that a generic test plan does not lock the 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

22 

evaluators into a test procedure that is not appropriate for the facility. More 

information on GCID’s Evaluation and Monitoring Program is available on their 

Web site (GCID, 2009). 

Figure 23. GCID’s Hamilton City diversion facilities located in an oxbow 

along the Sacramento River. 

 

The GCID flat plate screens are an unprecedented 1,100 ft long. According to the 

California Department of Fish and Game (CDFG) screening criteria, approach 

velocities for in-river screens should not exceed 0.33 feet per second (ft/s) over 

the entire screen face (CDFG, 2000). Measuring multiple locations on each of the 

85 screen panels to ensure adequate uniformity is prohibitively time consuming. 

However, one single velocity point measurement per screen does not adequately 

represent the flow patterns over the entire screen because a single measurement 

can be affected by localized debris effects or recirculating flow patterns. In this 

situation, the number of screen measurements that can be collected during a single 

evaluation is dictated by the design and flow conditions for the facility. The 

oversight agency should be contacted to discuss potential options. 

Screening criteria state that the sweeping velocity should be at least two times the 

allowable approach velocity at GCID. The flat plate screens were designed to 

have high sweep to approach velocity ratios, often around 10:1 or more. This 

larger ratio provides good hydraulics for safe fish exclusion, but it complicates 

screen evaluations. When mounting instruments in high velocities, the mount 

may vibrate or bend, particularly if the support is long or cantilevered 

(CH2M HILL, 2003). If a boat is necessary for installation, high velocities may 

make it difficult to maintain a steady boat position in the channel. High sweeping 
Field Evaluation Case Studies 

23

flows accentuate the influence of boundaries and obstacles in the flow. Since the 

approach velocity is a small component of the channel velocity, slight changes in 

flow conditions can substantially alter the magnitude of the approach velocity. 

Unlike controlled canal systems, on-river screening facilities face dynamic flow 

conditions. The GCID screens are located on an oxbow with a curved intake 

channel. Flow conditions such as upwelling, eddies, and recirculation currents are 

common. For these conditions, data repeatability may be problematic. 

Both ADVs and EM meters have been used successfully at the GCID site. 

Initially, the support structures for the screen cleaning brush masts were used to 

deploy multiple velocimeters. However, field tests at GCID have shown that the 

brush masts affected near-screen velocities up to 10 ft upstream from the masts, 

thereby skewing velocity data (Thomas, 2004). Consequently, a magnetic mount 

(shown in figure 24) was designed to be independent of the support structure in 

order to eliminate the hydraulic effects generated by the brush masts (Thomas, 

2006). 

An ADCP was 

successfully used as a 

support instrument at 

GCID during a field 

evaluation (Vermeyen 

and DeMoyer, 2002). 

Along with bathymetric 

and velocity data 

collected in and around 

the gradient restoration 

facility, cross sectional 

current profiles were 

collected across the 

GCID pumping plant 

approach channel and 

along the length of the 

fish screen. An example 

of the high resolution 

bathymetric and 

velocity field 

information collected by 

the ADCP is shown in 

figure 25. 

 

Figure 24. Magnetic ADV mount used at GCID 

(photo courtesy of National Marine Fisheries 

Service). 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

24 

Figure 25. Cross section of velocity magnitudes collected in the GCID pumping 

plant approach channel. 

Roza Fish Screens Facility 

Facility type: In-diversion drum screens 

Challenges: Access to drum screen face, defining velocity uniformity for a large 

facility 

Roza Diversion Dam is part of the Roza Division of Reclamation’s Yakima Basin 

Project. The dam diverts water from the Yakima River into the Roza Canal, 

which provides water for irrigation and power generation. Located at the canal 

headworks, a series of rotating drum screens protects fish from being entrained in 

the canal. The Roza Fish Screens Facility consists of 27 drum screens (17 ft in 

diameter and 12 ft wide) in five bays with a primary fish bypass at the 

downstream end of each bay (figure 26). 

Hydraulic evaluations have been conducted at the fish screening facility since 

1985 to document postconstruction performance (Abernathy et al., 1989) and to 

evaluate potential operational changes such as reducing primary bypass flows 

(McMichael et al., 2003; DeMoyer, 2004) and using sluice gates behind the drum 

screens for velocity control (DeMoyer and Vermeyen, 2004). Anadromous 

salmonid criteria are governed by the regional NMFS division (1995). Although 

governing approach velocity criteria specifies 0.4 ft/s, the facility was originally 

designed for an approach velocity of 0.5 ft/s. Evaluations have been conducted 

with consideration of the design criteria. 
Field Evaluation Case Studies 

25

Figure 26. Rotating drum screens in one bay of Roza Fish Screens 

Facility. 

There are unique challenges for measuring velocities near drum screens. Drum 

screens are designed for the expected approach velocity based on the vertically 

projected open area; however, for velocity evaluations, criteria require that the 

measurement occur 3 inches from the cylindrical screen face. A velocity meter 

can be easily positioned close to the screen face at or above the centerline of the 

drum. However, access to the screen face below the curvature of drum screens is 

difficult, particularly for large diameter screens such as the Roza screens 

(figure 27). 

Figure 27. A cantilevered steel mount with a horizontally adjustable arm 

was used to measure velocities close to the screen face near the 

surface (as shown) and under the curvature of the screen (DeMoyer, 

2004). 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

26 

Due to limitations in the body shape of the ADV instrument, standard downlooking ADVs cannot measure velocities at 3 inches from the screen at depths far 

below the screen curvature while maintaining a vertical probe orientation. At the 

Roza Fish Screens Facility, the velocity instrument may be as far as 30 inches 

from the screen face at 0.8 times the depth (figure 28). Inverting the probe may be 

possible, depending on the distance from the floor, sturdiness of the instrument 

mount, and debris and silt accumulation on the floor, but it is not recommended 

for large diameter screens where lack of visual cues increases the probability for 

probe damage. If an ADV cannot be positioned at the required location, the 

evaluation report should include the actual measurement location. Depending on 

the geometry of the site, EM meters may be placed slightly closer to the screen 

face under the curvature of the screen, but the use of multiple instruments may 

require separate mounting devices. 

Figure 28. Schematic of measurement locations at a distance of 

3 inches from the screen face and along the vertical projection of the 

screen (Abernathy et al., 1989). 

If the definition of velocity uniformity is not specified in the screening criteria, it 

is important to determine which data locations are required to adequately map 

velocities over the face of the screen. In a 1989 Pacific Northwest National 

Laboratory study at the Roza Fish Screens Facility (Abernathy et al., 1989), 

velocity measurements were collected at depths of 0.2, 0.5, and 0.8 on a vertically 

projected plane and at 0.05, 0.08a, and 0.9 near to the drum screen face, as shown 

in figure 28. Results indicated that velocities measured at 0.05 and 0.5 were 

accurately represented by measurements at 0.2 and 0.8 on the vertically projected 
Field Evaluation Case Studies 

27

plane. Limited velocity data collected near to the screen face at 0.8a and 0.9 

indicated that velocities may be higher at those locations, possibly due to a 1-foot 

drop in the floor elevation at the drum screens or the influence of the sluicing 

panels. 

Judgment should be used when selecting appropriate measurement locations for 

the evaluation under schedule and budget constraints. A hydraulic evaluation was 

conducted in March 2004 to determine the effects of sediment sluicing panels on 

drum screen performance. Data were collected on all 27 screens in 5 bays for 

2 different operational conditions. Changing the position of the sluicing panels 

was time intensive and required a significant equilibrium period before data 

collection could continue. In order to collect a full suite of data during similar 

diversion rates, six measurement locations were chosen per screen (two depths 

and three lateral locations). In an August 2004 evaluation, detailed velocity data 

were collected on representative screens in order to document the effect of 

lowering bypass flows. For this evaluation, 35 locations (5 depths and 7 lateral 

locations) were measured at 6 representative screens. 

Red Bluff Research Pumping Plant 

Facility type: In-diversion V-screens 

Challenges: Baffle installation due to high approach velocities and poor 

uniformity, flow deceleration into bypass 

Starting in 1966, Red Bluff Diversion Dam allowed gravity diversion from the 

Sacramento River into the Tehama-Colusa Canal for water deliveries. Operation 

of the diversion dam adversely impacted the fisheries resources in the river. In 

1995, Red Bluff Research Pumping Plant (figure 29) was constructed downstream 

of the Red Bluff Diversion Dam to test a new concept in fish protection at a 

pumped water diversion. This “pump first, screen second” method employed 

existing technology such as fish-friendly pumps (Archimedes lifts and an internal 

helical pump), vertical wedge-wire screens, and fish bypass structures. 

The fish-friendly pumps discharge water, fish, and debris into a concrete 

sluiceway. A V-shaped (or chevron) screening structure consists of twelve 5.25-ft 

by 5.25-ft steel panels. The screening structure concentrates the entrained fish 

into a bypass that conveys 10 percent of the total pumped flow (figure 30). The 

open channel bypass moves fish into the evaluation facility or back into the river, 

while the water passing through the V-screens continues into the canal. No 

baffles were included in the original screen design. Continuously operating 

brushes sweep both sides of the screen to minimize debris accumulation. 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

28 

Figure 29. Overview of Red Bluff Research Pumping Plant. 

Figure 30. Flat plate V-screen with a terminal fish bypass. 

Hydraulic evaluations were conducted throughout the facility to test the new fish 

protection methods employed at Red Bluff. In order to evaluate fish passage 

through the two types of pumps, the V-screens needed to be operating properly. 

An acoustic Doppler velocimeter was used to collect velocity data in front of the 

screen panels. The V-screens were designed to meet the CDFG approach velocity 

criteria of 0.33 ft/s maximum at 3 inches from the screen face. In 1997, 

CDFG accepted a fish screening criteria modification published by the Southwest 
Field Evaluation Case Studies 

29

Region NMFS (1997) specifying that approach velocities 3 inches from the screen 

face should not exceed 0.4 ft/s in canals. Initial screen measurements with no 

baffles resulted in approach velocities in excess of 1.25 ft/s. To reduce approach 

velocity magnitudes and improve flow uniformity, several baffle configurations 

were subsequently installed and tested. 

Screening evaluations were conducted 

from 1995 through 1998 to determine 

which baffle configuration produced the 

best screen performance (Frizell and 

Atkinson, 1999). Both fixed area baffles 

and adjustable porosity baffles installed 

behind the downstream half of the screen 

panels on both sides were not successful 

at meeting criteria. In order to affect the 

entire flow field, fixed area baffles were 

also installed behind the upstream half of 

the screen panels. A full set of baffles 

was needed to produce acceptable 

velocities in most areas of the screens 

(figure 31). Even with baffles, surface 

waves caused inconsistent velocities at 

the water surface due to the pump outlet 

conditions and short approach channel 

length to the screens. 

Mean channel velocities were measured 

at three locations approaching and inside 

of the screening structure. Results showed an undesirable deceleration of flow 

into the bypass. The bypass intake design produced a recirculation zone in the 

bottom 2 ft of the water column, causing the velocity to decrease. Although 

retrofits were difficult for this facility, structural modifications may be made at 

other sites if fish are not accelerated into the bypass. 

Submerged Cylindrical Screens 

Facility type: In-river or in-diversion submerged cylindrical screens 

Challenges: Instrument mounting, requires divers, variable approach conditions 

A specific case study will not be presented here, but the challenges of collecting 

cylindrical screen measurements will be discussed. Field evaluations of 

cylindrical screens on small diversions (less than 40 ft3

/s) are not common 

because the impact to fish is likely to be minimal. Field evaluations of large 

submerged cylindrical screens (above 40 ft3/s) may be required by regulatory 

agencies. 

Figure 31. Adjustable baffles 

located behind fish screen panels. 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

30 

Alternative screening technologies, such as submerged cylindrical screens, are 

becoming more commonplace because of the lower installation costs. Cylindrical 

screens are fixed in place either on a buried manifold system or to flanges on civil 

works projects. Other designs incorporate screens on retractable rails attached to 

the diversion pipe or the pumping plant structure, allowing maintenance to be 

carried out in the dry. When planning for the installation of submerged 

cylindrical screens, the approach conditions should be conservative to simulate 

the worst-case operational scenario. The screen should be placed in a location 

with uniform approach flow conditions, and the long axis of the screen should be 

parallel to the sweeping flow direction. Internal baffling is used to create more 

uniform velocity distributions over the screen face. Since baffles are not 

adjustable in most cylindrical screens, postinstallation modifications are typically 

limited to adjusting approach conditions or the angle of the screen. 

Laboratory tests at Reclamation’s Hydraulics Laboratory in Denver, Colorado, 

have shown that flow separation and eddies are generated off of the leading edge 

of the screen, causing water to flow out of the screen near the upstream end 

(Mefford and Hanna, 1997). During the screen tests, outflow occurred in the 

upstream 10 to 15 percent of the screen, producing higher approach velocities 

along the rest of the screen than the screen was designed to accommodate. With 

this in mind, additional open area should be provided to account for flow 

separation effects at the leading edge. 

Submerged cylindrical screens are often evaluated by manufacturers in a 

hydraulics laboratory for fisheries compliance under a range of flow conditions. 

Although these are good baseline evaluations of screen performance, changes in 

river flow and stage affect the flow angle and sweeping velocities near the screen 

in the field. Therefore, field evaluations should be conducted for a wide variety 

of flow conditions to fully evaluate screen performance. Submerged cylindrical 

screens are difficult to test in the field because of the complexity of installing and 

mounting velocity meters and uncertainties about the instrument location and 

percent of area tested. Retrievable screens can provide more flexibility than fixed 

screens in designing an evaluation plan. Regardless of screen type, divers will 

likely be needed to ensure proper placement of the velocity instrument and to 

reduce the possibly of damage to the instrument. When high sweeping velocities 

exist, the risk associated with having divers in the water is heightened. Holding 

the velocity meter in place is not a viable option; therefore, the diver must either 

move the instrument and reattach it between measurement points or an instrument 

mount must be designed to move the meter along the screen without obstructing 

flow patterns. 
Field Evaluation Case Studies 

31

Tracy Fish Collection Facility 

Facility type: Louver system 

Challenges: Maintaining high bypass flows, flow deceleration and eddying near 

bypasses, debris loads 

The Tracy Fish Collection Facility (TFCF) is located at the head of the DeltaMendota intake channel at the south end of the Sacramento-San Joaquin Delta 

near Tracy, California. The facility was constructed in the 1950s to collect fish 

before entrainment at the C.W. “Bill” Jones Plant. The facility was designed to 

guide fish from the canal into one of four primary bypass intakes by way of a 

diagonal line of louvers in the primary channel. Two sets of louvers in a 

secondary facility guide fish through a bypass into the holding tank area. A 

schematic of the facility is seen in figure 32. 

Figure 32. Plan view schematic of the Tracy Fish Collection Facility near Tracy, 

California. 

Fisheries criteria for louver systems have not been published by regulatory 

agencies; however, standards for operation of the TFCF are published in Decision 

1485 Water Quality Standards for the Sacramento-San Joaquin and Suisun 

Marsh (State Water Resources Control Board, 1978). According to table II, 

the secondary channel velocities should be held at 3.0 to 3.5 ft/s from 

February - May, while salmon are present, and less than 2.5 ft/s from 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

32 

June 1 - August 31 for striped bass, shad, and catfish. The bypass entrance 

velocity should exceed the local channel velocity to guide fish into the bypass. 

This ratio, defined as the bypass ratio, should be greater than 1.0 to achieve 

efficient bypass conditions and to eliminate eddies and slack water zones that hold 

up fish movement. 

Like screening facilities, to achieve effective fish exclusion, the fish must be 

moved efficiently along the louvers with gradual flow acceleration into the 

bypass. Strong accelerations and decelerations can cause fish avoidance of the 

bypass (Bates et al., 1960). In 2004, the primary bypass intakes were replaced 

with a new design based on physical and computational hydraulic studies 

(Kubitschek, 2003). The new bypasses were designed to produce a near-uniform 

vertical flow distribution throughout the water column to improve the hydraulic 

conditions for fish collection. Laboratory modeling also showed that vertical 

approach flow velocity distributions strongly influence velocity distributions 

within the bypass intake, so it was anticipated that the bypass intakes would 

perform best when debris fouling was minimized (Johnson et al., 2004). 

Hydraulic field evaluations were conducted to verify the performance of the new 

primary bypass intakes (DeMoyer, 2007). 

Vertical velocity profiles were collected at the bypass intake with an acoustic 

Doppler velocimeter. Since the bypass channel is only 6 inches wide, an 

instrument mount had to be designed to minimize flow blockage and disturbance 

to flow patterns. An angled rail was attached to the louvers with a vertically 

traversing sled (figure 33). The ADV was mounted on the end of an arm 

extending from the moveable sled to measure vertical velocities at the bypass 

intake. An acoustic Doppler profiler was used to measure velocity field 

distributions upstream of the intake. The instrument was tethered to the louver 

cleaner platform in order to position the instrument properly in front of the bypass 

(figure 34). 

 

Figure 33. Mounting an ADV to the 

louver line. 

Figure 34. Positioning the ADP in front 

of the bypass intake. 
Field Evaluation Case Studies 

33

Field results showed that bypass ratios greater than 1.0 minimize flow disruption 

and eddying and promote gradual flow acceleration into the intakes, indicating 

that the facility should be operated in this manner whenever possible. However, 

tidal fluctuations, high pumping rates, and low water levels in the Delta prevent 

achievement of bypass ratio objectives at times, regardless of facility operation. 

High debris loads adversely affected bypass performance by degrading uniformity 

in the vertical velocity profiles at the bypass entrances. This shows the 

importance of debris management at fish protection facilities. 

References 

35

References 

Abernathy, C. Scott, Duane A. Neitzel, and E. William Lusty. 1989. Velocity 

Measurements at Six Fish Screening Facilities in the Yakima River Basin, 

Summer 1998, Annual Report. Pacific Northwest National Laboratory, 

Portland, OR. 

Bates, Daniel W., Orren Logan, and Everett A. Pesonen. 1960. Efficiency 

Evaluation, Tracy Fish Collection Facility, Central Valley Project, California.

Bureau of Reclamation, Region 2, Sacramento, California, and Bureau of 

Commercial Fisheries, Pacific Region, U.S. Fish and Wildlife Service, 

Seattle, WA. 

Bureau of Reclamation. 2006. Fish Protection at Water Diversions. Water 

Resources Technical Publication, U.S. Department of the Interior, Bureau of 

Reclamation, Denver, CO. 

Bureau of Reclamation. 2001. Water Measurement Manual – 3rd Edition. Water 

Resources Technical Publication, U.S. Department of the Interior, Bureau of 

Reclamation, Denver, CO. 

California Department of Fish and Game. 2000. Fish Screening Criteria. 

CH2M HILL. 2003. Glenn-Colusa Irrigation District Fish Protection 

Evaluation and Monitoring Program – 2003 Annual Report. 

DeMoyer, C.D., and T.B. Vermeyen. 2004. Roza Fish Screens Facility Velocity 

Measurements With and Without Porosity Boards at an Intermediate Canal 

Flow Rate. Report No. PAP-928, Bureau of Reclamation, Water Resources 

Research Laboratory, Denver, CO. 

DeMoyer, Connie. 2004. Roza Fish Screens Facility: Velocity Measurements at 

a High Canal Flow Rate. Report No. HL-2004-06, Bureau of Reclamation, 

Water Resources Research Laboratory, Denver, CO. 

DeMoyer, Connie. 2007. Hydraulic Performance Evaluation of the Replacement 

Primary Bypass Intakes and Transition Boxes at Tracy Fish Collection 

Facility. Tracy Fish Collection Facility Studies, California, Volume 40. 

Frizell, K.W., and S.P. Atkinson. 1999. Engineering Evaluation of the Red Bluff 

Research Pumping Plant on the Sacramento River in Northern California: 

1995-1998. Red Bluff Research Pumping Plant Report Series Volume 6. 

Bureau of Reclamation, Denver, CO. 
Guidelines for Performing Hydraulic Field Evaluations at Fish Screening Facilities 

36 

Glenn-Colusa Irrigation District. 2003. Fish Screen Improvement Project. 

http://www.gcid.net/FishScreen.html. Accessed on October 7, 2008. 

Johnson, Perry L., Morris Campbell, and James A. Higgs. 2004. Physical Model 

Study of a Primary Bypass Intake with Louvers at the Tracy Fish Collection 

Facility, Tracy, California. Tracy Fish Collection Facility Studies, California, 

Volume 28. 

Kubitschek, J.P. 2003. Physical and Computational Model Studies to Improve 

Hydraulic Performance at the Primary Bypasses at Tracy Fish Collection 

Facility, Tracy, California. Tracy Fish Collection Facility Studies, California, 

Volume 19. 

McMichael, G.A., J.A. Vucelick, and C.S. Abernathy. 2003. Roza Dam Fish 

Screen Evaluations, Summer 2003. Battelle-Pacific Northwest Division, 

Richland, WA. 

Mefford, Brent, and Leslie Hanna. 1997. Model Tests of Air Burst and Hydraulic 

Back-Flush Cleaning Efficiency for a Cook Cylindrical Screen. Bureau of 

Reclamation. Hydraulics Laboratory Report PAP-770, Denver, CO.

National Marine Fisheries Service. 1997. Fish Screening Criteria for 

Anadromous Salmonids. National Marine Fisheries Service, Southwest 

Region, Santa Rosa, CA. 

National Marine Fisheries Service. 1996. Addendum: Juvenile Fish Screen 

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