1974 WALUATION OF THE GLENN-COLUSA 

IRRIGATION DISTRICT FISH SCREENYY 

Ronald J. DecotoY 

Bay-Delta Fishery Project 

ABSTRACT 

Marked hatchery-reared king salmon were released and 

recaptured to observe their responses to trashracks 

and the fish screen, and to determine bypass and 

screen effectiveness. 

Some salmon released between the trashrack and drum 

screens found culverts downstream from the screens 

on bypass flows less than 5 percent of the channel 

inflow. 

Eighteen ercent of the marked salmon used the bypasses, 3f percent used a pair of culverts installed 

in the diversion dam. Fate of the remaining 82 and 

66 percent is unknown. 

Nets behind selected dmm screens and in the irrigation canal below the pumps caught salmon. Hence, 

an unknown number of salmon are lost through the 

screens. 

Most fish were captured during twilight and dark. 

r/ This study was conducted as part of the Znteragency Ecological Study.Program for the Sacramento-San Joaquin Estuary whose members include: 

California Department of Fish and Game, California Department of' Water Resources, U. S, Bureau 

of Reclamation, and U. S. Fish and Wildlife Service. 

Anadromous Fisheries Branch Administrative Report

No, 78-20. September, 1978. 

PPresent address: Route 1, Box 249, Westwood, CA 

961379 
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INTRODUCTION 

King salmon (Oncorhynchus tshawytscha) spawn in the upper Sacramento River and its tributaries. During their downstream migration, large numbers of young salmon are diverted from the Sacramento River via a side channel to the Glenn-Colusa Irrigation

District's canal intake. The intake is screened by a series of 

horizontal rotary drum screens, which incorporate a bypass system to transport screened fish back to the channel below the diversion dam, which then returns to the Sacramento River. 

Fish movements at the facizity were monitored from May 15 to 

July 25, 1974. Objectives were to: (i)observe response of 

juvenile salmon to the screens, (ii)evaluate ability of salmon 

to move down tream below the diversion intake under low channel

flows E.5 m5/see (90 cfs)] , (ifi)determine response of salmon to the trashrack and screens, and (iv) determine efficiency

of the bypasses in salvaging salmon. 

DESCRIPTION OF AREA AND DIVERSION FACILITIES 

The Glenn-Colusa fish screen is 5.6 Icm (3.5 mi) northwest of 

Hamilton City, Glenn County, California (Figure 1). The screen 

is on an oxbow formed by an island on the west bank of the Sac-. 

ramento River. About 10-18percent of the river flow passes

through the. oxbow. 

During irrigation season, usually late March through October, 

a dam is installed downstream from the fish screen to provide

head for the pumps. A pair of culverts 0.9 m (3 ft) in diameter were installed in the diversion dam specifically for this 

study (Figure 2). 

The fish screen complex consists of a concrete structure 145 m 

(475 ft).long, 9 m (30 ft) high, and 9 m (30 ft) wide. The 

structure houses 40 horizontal rotating drum screens each 5.2 m 

(17ft in diameter and 2.4 m (8 ft) wide. The drums are covered 

with #2 woven stainless steel wire cloth. Open space between 

the 2.03 mm (0.08 inch) diameter wire is 4.3 mm (0.17 inch).

There are ten 15.2 em (6 inch) wide bypasses, one located at 

the downstream end of every fourth screen. These all join and 

lead to the bypass outlet (Figure 2). A trashrack keeps large debris from entering the screen wells. The screens are rotated 

by 10 hydraulic pumps that move the drums at 1.4 m (4.5 ft> per

minut e. 

The scree s operate during the irrigation season and divert up

to 76.5 m3/s (2,700 cfs) from the river. Design approach velocity at the screens is 0.2 m (0.8 ft) per second. The drums are 

removed in w'inter. 
IRRIGATION CANAL 

TO HAMILTOM CITY 

1,- LOCATION OF STUDY AREA. 
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RIVER I___t 

fRRlOATION DIVERSION CHANNEL 

ISLAND 

NORTH 

DRUM SCREENS 

NElTiNG SITES 

\' 

FIGURE 2.- STUDY AREA (NOT BRAWN TO SCALE 
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METHODS 

Fish Marking 

Fingerling king salmon (16,430) were obtained from the Feather 

River Salmon and Steelhead Hatchery and marked by clipping single fins. For culvert tests an upper-lobe caudal clip was used 

for fish released between the trashrack and screens, and a lower-

“ lobe caudal clip was used for fish released in the channel opposite the screens. During bypass monitoring a right ventral fin 

clip was used for fish released between the trackrack and screens 

and a left ventral fin clip for fish released in the channel. 

Fish were anesthetized in a 0.01 percent solution of M.S. 222 

(tricaine methanesulfonate) to facilitate marking. Fish were 

held at the hatchery for at least two days after marking to reduce use of “sickll fish. Measurements of fork length (FL) were 

taken, and are used throughout this report. 

Bypass Monitoring 

Between May 15 and July 25, 1974, the bypass outlet was sampled

with a rigid frame fyke net attached directly to the outlet structure (Figure 2). The net was 2.7 m high by 3.0 m (9.7

ft) wide at the opening and 20.0 m ( long. The mesh was 

3.2 rnm (1/8 inch) bobbinet. A live box was attached to the cod 

end of the net to collect fish from the bypass. 

Three paired tests were conducted to evaluate ability.of salmon 

to move past the drum screens and enter the bypasses, and to test 

the effect of the trashrack on the returns. A total of 2,992 

marked salmon were released between the trashrack and screens 

and 2,903 were released in the channel opposite the screens 

(Figure 2). During each bypass test the culverts in the diversion dam were closed and the bypass was monitored for 48 hours 

following a release 

The fyke net was checked every two hours and fish were removed 

from the live box. All. species were enumerated and the salmon 

a were examined for marks. Daily, three collections of salmon were

measured to the nearest even millimeter. 

Between tests the bypasses were monitored to estimate the number i* of wild downstream migrant salmon passing the facility. 

Culvert Monitoring 

B.0 different-sized nets were used to monitor the culverts. ~ i Both were attached directly to a frame at the c.ulvert outlet. 
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Culvert monitoring began June 12 and continued until June 14 

with a 2.9 m (9.5 ft) square opening fyke net 15.2 m (50 ft)

in length. This net was replaced on June 14 to facilitate handling of the live box upon retrieving a sample. The latter net 

was 3.0 m (9.7 ft) wide by 2.7 m (8.7 ft) high at the mouth and 

65.5 ft) long. Both culvert nets were constructed of 

1/8 inch) bobbinet. 

From June 12 through July 19, the culverts were monitored alternately with the bypasses. Five paired tests were conducted to 

determine if salmon would locate the culverts and move downstream 

through them on 3-5 percent of the inflow. A total of 5,399 

marked salmon were released in the channel and 5,136 between 

the trashrack and screens. During each culvert test the bypasses were closed and the culverts were monitored for 48 hours 

following a release. Monitoring and enumeration methods were 

the same as those in the bypass monitoring. 

Comparison of Bypass and Culverts 

One test was conducted July 16, 1974 to determine preferences

for the bypasses or culverts during four hours in which both 

systems were open. Catches of culve t and bypass nets were 

enumerated hourly. Flows were 2.5 m5/s (90 cfs) through the 

bypasses and 2.3 m3/s (80 cfs) through the culverts. 

Rotary Drum Screen Evaluation 

3etween May 21 and June 4, two nets of different sizes were 

fished continuously for 168 hours in the irrigation canal directly downstream from the main pump house (Figure 2). The 

purpose was to study the adequacy of rotary drum screens in 

salvaging young salmon. The flrst net was fished for two 

days. It was 2.6 m (8.5 ft) high by 2.9 m (9.5 ft) wide at 

the opening and 15.2 m (50ft) long. The mesh (stretched)

raduated from 7 cm (2-75 inches) at the mouth to 4.4 cm 

1.75 inches) at the cod end. The second net measured 3.2 m 

10.5 ft) high by 4.9 m (16 ft) wide at the openin and 18 rn 

59 ft) long. Its mesh was graduated from 7.6 cm 73 inches) 

to 1.3 cm (0.5 inch). 

A fyke net was fished behind three separate screens for five 

days in September, for a total of 76.5 hours. This net was 

the same as first used to monitor the culverts. The net was 

attached to a rigid frame placed in guide slots directly behind the screen. 
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RESULTS 

Bypass and Culvert Monitoring 

Marked Salmon 

During bypass tests, an average of 18 percent of the fish released 

were recovered from the bypass outlet. Twenty percent of those 

released between the trashrack and screens were recovered, while 

16 percent of the fish released in the channel opposite the screens 

were recovered (Table 1). A chi square test revealed the difference in recoveries between the two release sites was significant at the 0.01 level (chi square = 16, d.f. - 1). 

During culvert tests, an average of 34 percent of the fish released were recovered in the culverts. Thirty-eight percent of 

those released in the channel opposite the screens were recovered, 

while 30 percent of the fish released between the trashrack and 

screens were recovered (Table 2). The difference was a ain significant at the 0.01 level (chi square = 68.1, d.f. = 17. 

Marked salmon moved through the bypass and culverts mainly during reduced light periods (2000-0600hours) (Figure 3). 

Wild Salmon 

Downstream migration of wild salmon was in progress when bypass

monitoring began May 15, and was continuing when monitoring ended 

July 25. These salmon used the bypasses, except when the culvert tests were being run. 

From May 15 to July 25, 13,299 wild salmon were captured at the 

bypass outlet. Peak catches occurred during May when the averper 24-hour trapping period yielded 1,300 salmon (Table 

e maximum 24-hour catch of 1,821 salmon occurred the week 

of May 13-19 (Figure 4; Appendix Table 1). Bypass catches declined after May 19 (Figure 4). The lowest catch was the week 

of July 15-21, which averaged 97 salmon per 24-hours of' trapping

(Figure 4; Appendix Table 1). 

A diurnal movement identical to that described for the marked 

salmon was observed in wild salmon. Movement was mainly during

reduced light periods (2000 to 0600 .hours), and totals of 73 

and 81 percent of the king salmon recovered moved through the 

culverts and bypass during this period (Figure 3). 

Bypass-caught wild salmon ranged from 28-120mm 11.1-4.7 inches) 

FL, Monthly mean fork lengths varied rrom a high of 82 mm (3.2

inches) in June, to a low of 72 mm (2.8 inches) in July (Figure 5; 

Appendix Figure 1)-
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TABLE 1 

Bypass Recoveries of Marked King Salmon 1974 

Area of I Total Marks Total Marks 'Percent Percent 

Release Released Recovered Recovered Not Recovered 

!Iehind 

Trash- I 2992 588 19.65 8035 

Channel 

' I 454 15.64 84.36 

1042 r/ 1168 8232 

TABLE 2 

Culvert Recoveries of Marked King Salmon 1974 

Area of I Total Marks I Total Marks Percent Percent 

Release Released Recovend Recovered Not Recovered 

30.06 69.94 

I 

37.11 62.29 

Totals I 18,535 I 33.98 66.02 
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BY PASSES 0 

CULVERTS -aBI-HOURLY MOVEMENT OF DOWNSTREAM MIGRANT KING 

SALMON THROUGH THE BY-PASSES AND CULVERTS 

(COMBINED DATA FOR 7 DAYS OF COMPLETE SAMPL 

ING FOR THE BY-PASSES AND 3 DAYS FOR THE 

CULVERTS) I 1974. 
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>

4 

3 

7 

W 

z 

3 

3 

> 

a 

n 

n 
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CULVERTS 

BY- PASSES -0­

.,qI1 1 

1 

1 

J 

1 

2 500- I 

1 

I 

I 

I 

I 

I

zoo0 i 

I 

I 

1 

1 

I 

I 

I 500- i 

f 

I 

I 

1 

I 

I 

t QOO 

500 

I : I I 1

000 I 

13-19 19-26 2f-2 3-5) 10-16 17-23 2430 1-7 8-14 15-21 22-28 

MBY dUNE JULY 

FIGURE 4. WEEKLY CATCH OF DOWNSTREAM MIGRANT 

KING SALMON. 

21 A FRESHET OCCURRED OURIMG JULY 8 14, RESULTING IM A HIOH CATCH. 
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TABLE 3 

Bypass Catches of Wild Hifig Salmon 1974 

Number of 

Month I Trap Hours 

May 98.8 

June 226.9 

July 263.2 

Totals I 588.9 I 

Wild Salmon 

Cailaht 

5352 

5075 

2872 

Catch Per 

24 -Trap Hours 

1300.1 

536.8 

261.9 

13,299 I I 

TABLE 4 

Culvert Catches of Wild King Salmon 1974 

Catch Per 

24-Trap Hours 

June I 163.8 I 5116 I 749.6 

136.5 7352 1292.6 L/ 

Totals I 300.3 I 12,468 I ­

r/ A freshet occurred July 8-14, resulting in a 

high catch, 
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3etween June 12 and July 19, 12,468 wild salmon were captured 

at the culvert outlets. The peak occurred in July, when average

catch per 24-hour trapping period was 1,293 salmon (Table 4).

The highest 24-hour catch (3,434) occurred following a freshet 

in the week of July 8-14. The lowest catch occurred the week 

of July 15-21 (average of 247 salmon per 2bhours) (Figure 4; 

Appendix Table 2). 

These salmon ranged from 32-110 mtn (1.2-4.3 inches) FL, Monthly 

mean fork lengths varied from a hi h of 83 mrn (3.3 inches) in 

June to a low of 74 mm (2.9 inches in July (Figure 5; Appendix

Figure 1). 

The diurnal migration observed in the bypass tests also occurred 

in the .culvert study. 

Comparison of Bypass and Culverts 

During a four-hour test on July 16, bypasses and culverts were 

opened simultaneously to assess fish movements. Mean catch per

hour of wild salmon was 18 and 8 through the culverts and the 

bypasses, respectively. This duplicated the 2:l ratio of recoveries of marked and wild salmon obtained in the independent tests. 

Rotary Drum Screen Evaluation 

.. . 

Nets fished in the irrigation canal caught 18 wild salmon in 

168 hours of sampling. Salmon captured in the canal ran ed from 

56-92 mm (2.2-3.6 inches) FL, ,with a mean size of 76 mm $3.0 

inches) FL, 

Of' the three bays in which fyke net sampling was conducted behind the screens, only one net caught fish, This net caught 55 

salmon during 38.5 hours (1.4 salmon per hour). These salmon 

ranged from 28-34 mm (1.1-1.3 inches) FL with a mean of 32 mm 

(1.2 inches) FL. 

DISCUSSION 

Bypass System 

Downstream migrant salmon are reluctant to use the bypasses. The 

narrow width of' the bypasses B5.2 em (6 inchesg , the gravity

operation, and sediment accumulation in the bypasses may be limiting its efficiency. Also, bypass entrance velocities may not be 

unifoym across the screen structure due to differences in head 

from sediment deposits, 
Ruggles and Ryan (1964) concluded that guiding efficiency increased from 51 to 67.percent when bypass width increased from 

15.2 em (6 inches) to 30.5 cm (12 inches). 

The pair of culverts in the diversion dam were twice as effective as the bypasses in passing salmon below the diversion dam, 

The wider opening at the entrance to tne culverts and the whirlpool caused by the diversion dam may have contributed to the 

greater utilization of the culverts. 

Trashra ck 

Marked salmon released between the trashrack and screens moved 

out and located the culverts, however the difference in return 

rates for both the culvert and bypass tests indicate the trashrack is having an effect on salmon movements (Tables 1 and 2). 

Salmon Survival 

The fate of the 66-82 percent of marked releases that did not 

utilize the b asses or culverts is undetermined. Four explanations are: (3they returned upstream and out to the river, 

(2) they were eaten by predators, (3) they escaped through the 

drum screens via the screen mesh and seals, and (4) combinations 

of the first three, 

Migratory Behavior 

The greatest numbers of salmon passed through the bypasses and 

culverts during darkness, This agrees with studies of entrainment of fish fingerlings at various water intake structures (Pavlov 1969). Pavlov concluded that during low illumination, the 

fishes’ ability to visually orient in a stream of water is reduced, thereby reducing their swimming ability and causing

them to become passive, 

CONCLUSIONS 

1. More fish passed through a pair of culverts than through the 

10 bypasses incorporated into the fish screen. 

2. The fate of 66-82 percent of the test fish not recovered in 

the bypass and culvert systems is unknown. 

3. The presence of a trashrack has an effect on salmon movements. 
4. 

5. 

Fish entrained between the trashrack and screens are able to 

move out and locate culverts downstream from the screens under low bypass flow conditions, although with a lower return 

rate than fish in the channel in front of the trashrack. 

Most outmigrant salmon moved during twilight and dark. 

ACKNOWLEDGEDENTS 

I thank John Skinner and William Heubach who designed and supervised the study. Special thanks to Jerry Wise who was invaluable 

in the collection of data and construction of equipment used in 

the study. Robert Clark and his staff from the Glenn-Colusa Irrigation District and Russell Franson and his staff from the Department of Water Resources provided continuing support. The Feathey

River Hatchery supplied marked salmon for the study. Thanks also 

to Dan Odenweller and Glenn Delisle for critically reviewing th5s 

report. 
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LITERATURE CITED 

Pavlov, D, S. 1969. Entrapment of fish fingerlings in pumping

installations as related to features of their behavior and 

orientation in the stream of water. Prob. of fchthyol. 

g(2) ~237-243. 

Ruggles, C. P. and P. Ryan. 1964. An investigation of louvers 

as a method of guiding juvenile Pacific salmon. The Canadian 

Fish Culturist, (33) ~6%. 
-- 

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APPENDIX TABLE 1 

Bypass Recoveries 

Number of 

trap hours 

24.5 

36.0 

45.8 

88.2 

39.0 

44.2 

48.0 

65.5 

68.5 

64.5 

64.7 

588.9 

of Wild King Salmon 

Recoveries of Catch per

wild salmon 24-trap hours 

1859 1821.1 

2627 1751.3 

1016 532-4 

1815 493.9 

1566 96307 

1145 621.7 

399 

761 278 8 

1506 527.6 

199 5 

261 97.1 

344 127 6 

13,299 

Week 

May 13-19 d 

19-26 

May 27-June 2 

June 3-9 

10-16 

17-23 

24-30 

July 1-7 

8-14 

I 15-21 

22-28 

Totals 

APPENDIX TABLE 2 

Culvert Recoveries of Wild King Salmon 

Week 

J June 10-16 

17-23 

24-30 

JU~Y 1-7 

8-14 

15-21 

Totals 

1 I I 

I

f 

667 5 

Number of 

trap hours 

Recoveries of 

wild salmon 

Catch per

24-trap hours 

34.8 632 435.9 

64.0 2649 t 993.Q 

65.0 1835 

45.5 705 371.9 

43.0 6153 3434.2 

48.0 494 247.0 

300.3 I 12,468 I -

I 

1 
50 

40 

30 

20 

10 

-J 5 0 Q

k 

0 40 

I30 

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APPENDIX FIGURE 1. 

LENGTH FREQUENCIES OF WILD DOWN 

STREAM MlGRANT KING SALMON C&P 

TURED THROUGH THE BY PASSES AND 

CULVERTS. 

JUNE 

BY-PA SSm &=82mm. 

c ULVERT 3=83mm. 

BY-PASS@ ~~72 mm, 

CULVER^ = 74 m m, 

22 32 42 52 62 72 92 102 112 12 

FORK LENGTH hm.1