Canals USBR

Question 1

Trapezoidal is the most accepted shape for earthern canals

T or F?

Answer 1

True

Question 2

Side slopes of 3:2 for smaller canals and laterals and 4:2 for larger canals is generally adequate for most earth materials and should be considered when determining the side slopes of canals

T or F?

Answer 2

True

Question 3

3.0 fps for smaller canals up to 1.5 fps for larger are the range of permissible velocities considered for sizing a canal water section

T or F?

Answer 3

False

Question 4

What considerations must be made when canal construction is to utilize “cut and fit” methods?

• The water prism should be kept a safe distance into the natural ground
• Generally the ground water surface above the downhill cut take should not exceed approximately one-fourth the water depth
• On steep sidehills the entire water prism should be entirely in the natural ground for safe consideration
• All above

Answer 4

All above

Question 5

Steel flumes are seldom used today due to High maintenance costs

T or F?

Answer 5

True

Question 6

Alone uphill terrain concrete bench flumes are most commonly used

T or F?

Answer 6

False

Question 7

What shape of flume gives the maximum velocity for a given area?

• One that has a bottom width 4 times the depth of the water depth
• One that has a bottom width 2 times the depth of the water depth
• One that has a bottom width 3 times the depth of the water depth
• None above

Answer 7

One that has the bottom width 2 times the water depth

Question 8

Encountered falling rock and debris are ideal conditions to make precast concrete pressure pipe for flume service

T or F?

Answer 8

True

Question 9

Buried precast concrete pipe and monolithic concrete pipe are considered common types of construction for siphon service

T or F?

Answer 9

True

Question 10

Why is concrete pipe predominantly used for canal siphons?

• Hydrostatic heads encountered are generally less than 150 ft
• Bridges supporting canal sections across drainage channels, over highways and railroads, are generally more expensive
• Sizes from 12 to 96 inches are available in most localities
• All above

Answer 10

All Above

Question 11

Monolithic construction is generally considered for siphons smaller than 96 inches in diameter

T or F?

Answer 11

False

Question 12

Factors that may dictate construction of elevated steel pipe siphons could be where costly rock excavation is encountered and limited space for handling river flows during construction

T or F?

Answer 12

True

Question 13

What essential design features, in addition to the pipe itself, must be considered for inverted siphons?

• Inlet and outlet transitions
• Blowoff structures
• Non pressured lines
• Both A and B

Answer 13

Both A and B

Question 14

Inlet and outlet transitions serve for the purpose of maximizing head loss and erosion damage

T or F?

Answer 14

False

Question 15

A pump type, gravity pump, and pressure turnout type, are all considered blowoff structures

T or F?

Answer 15

True

Question 16

When feasible, blowoffs should be located at the low points of siphon where water is drained into natural drainage channels

T or F?

Answer 16

True

Question 17

To dislodge sediment and debris that may become packed in the discharge line immediately upstream of the blowoff valve is the purpose of the high velocity jet utilized in some gravity blowoffs

T or F?

Answer 17

True

Question 18

To convey water over relatively steep slopes to lower grades and water surfaces in canals or laterals is the purpose of chute (drop)

T or F?

Answer 18

True

Question 19

What purpose do the controlled notch or stoplogs serve in the inlet transitions of drops and chutes?

• Prevents sedimentation from buildup
• Prevents drawdown at the entrance that would cause erosion of canal
• Prevents flooding
• None above

Answer 19

Prevents drawdown at the entrance that would cause erosion of canal

Question 20

If maximum velocities are more than 3.5 fps, an outlet transition is generally not necessary

T or F?

Answer 20

False

Question 21

By providing a depressed (submerged) section of pipe ahead of the outlet transitions, superficial velocities are dissipated in pipe drops

T or F?

Answer 21

True

Question 22

Water Hammer is a reason why open type stilling pools or impact basins utilitze outlet transitions for pipe chutes

T or F?

Answer 22

True

Question 23

What is the preferred shape of a monolithic reinforced concrete chute?

• circle
• triangle
• rectangular
• missing

Answer 23

rectangular

Question 24

Besides stoplogs, siphons are devices used to control water levels at the inlet of monolithic reinforced concrete drops and chutes

T or F?

Answer 24

False

Question 25

The energy dissipated by the blocks constructed along the floor of the chute is when a conventional stilling pool is utilized in the baffle apron drop. T or F?

Answer 25

False

Question 26

Cross drainage structures serve the purpose to protect canals from damage from algae T or F?

Answer 26

False

Question 27

Relative capacity of canal with respect to drainage flows and canal water surface with respect to natural ground surface dictates the need of cross drainage T or F?

Answer 27

True

Question 28

Where the canal is carried across a natural drainage channel upon an embankment, culverts are used for cross drainage T or F?

Answer 28

True

Question 29

For large canals, what storm frequency is used to develop culvert size? - 500 year storm frequency - 100 year storm frequency - missing - missing

Answer 29

100 year storm frequency

Question 30

The purpose that pipe collars serve in culvert constructions is to prevent water seepage in discharge line T or F?

Answer 30

False

Question 31

What conditions dictate the use of an overchute? - Where the waster surface of the canal is below the natural water surface - Where loss in grade in the canal is not permissible - Are generally found economical on large canals where the drainage flows are small by comparison to canal flows - All above

Answer 31

All above

Question 32

When the amount of drainage water is large by comparison to the canal is what make drainage inlets acceptable T or F?

Answer 32

False

Question 33

Two important factors that dictate the placement of a drainage inlet intake are that the intake must be located below the maximum water surface elevation and at the natural ground level surface T or F?

Answer 33

False

Question 34

Flow control and flow measurement are considerations for regulating structures T or F?

Answer 34

True

Question 35

What devices are generally employed for flow control? - Pumps - Slide gates - Lift gates - Generators - Radial steel gates

Answer 35

- Slide gates - Lift gates - Radial steel gates

Question 36

Parshall flume and cipolleti weir are two mearuring structures for turnouts T or F?

Answer 36

True

Question 37

Wasteways serve the purpose so that they are utilized to dispose excess water from canals and to safely empty canals in case of canal break or emergencies. T or F?

Answer 37

True

Question 38

A sudden decrease in discharge when the siphon primes is detrimental to the wasteway channel and would be considered in disadvantage of siphon spillways. T or F?

Answer 38

False

Question 39

Overflow spillway without gate control is the type of wasteway construction that is preferred T or F?

Answer 39

False

Question 40

Checks serve the purpose to control the flow of water when at partial capacity T or F?

Answer 40

True

Question 41

Two general types of checks used in small canals are those using flashboards for regulation, or a combination of gates and flashboards for regulation. T or F?

Answer 41

True

Question 42

Radial gate checks of the California Aqueduct always employ overflow weirs T or F?

Answer 42

False