AREA 2: LAND AND WATER RESOURCES ENGINEERING AND ALLIED SUBJECTS (VOLUME 6 )

PROBLEM 1: The conveyance loss in a 400 m-long unlined parabolic canal with a top width of 1.5 m when the flow depth is 0.8 m assuming a S&P loss rate of 3.33 x 10^-6 m^3/s per m^2 is _____.

PROBLEM 2: Given the following cumulative infiltration equation: F=8.1t – 0.32e-12.9t , where F is in mm and t is in hours. If the rainfall intensity after 20 minutes is 10.0 mm/hr, the actual rate of infiltration is ____.

PROBLEM 3: A 4-in diameter shallow tubewell has been installed to pump water from a confined aquifer with a transmissivity of 200 m2/day and a radius of influence of 300 m. The steady state drawdown in the well is 4.5 m. During land preparation period, the land soaking requirement is 13.4 mm/day, evaporation loss is 3 mm/day and seepage and percolation amount to 2 mm/day. Assuming a standing water depth of 1.0 mm/day and an application efficiency of 70%, which of the following is true?

a. The steady state well discharge is 12.8 lps b. The farm water requirement is 3.21 lps for 2 hectares c. The farm water requirement is greater than the groundwater supply d. One shallow tubewell is adequate to irrigate 2 hectares

PROBLEM 4: A 25-inch diameter 2-meter long culvert has been designed to carry a maximum discharge of 700 lps when flowing half-full. Its roughness coefficient n is 0.015. If the inlet and the outlet are both unsubmerged, the difference in elevation between the inlet and the outlet should be

a. 5 cm

b. 7.5 cm

c. 10 cm

d. 12.5 cm

PROBLEM 5: Given the following hydrograph taken in the mainstream of a 12 sq. km watershed:

HOUR                 DISCHARGE(lps)

0400                       350

0700                        1100

1000                         2150

1300                         2950

1600                         2570

1900                         1960

2200                         1330

0100                         1000

0400                         810

0700                         680

1000                         580

1300                         500

1600                         440

1900                         410

2200                         400

Assuming a baseflow that is practically close to 200 lps, the depth of excess rainfall is

a. 15.4 mm

b. 12.8 mm

c. 10.2 mm

d. 8.4 mm

PROBLEM 6: The critical depth in a triangular open channel with a side slope z=2 for a discharge of 2.0 m^3/s is ___.

a. 0.86 m

b. 0.72 m

c. 0.61 m

d. 0.54 m

PROBLEM 7: The most hydraulically efficient concrete-lined trapezoidal channel section with a bottom slope of 0.1% to carry a discharge of 2.0 m3/s has a bottom width of ___.

a. 1.0 m

b. 1.1 m

c. 1.28 m

d. 0.95 m

PROBLEM 8: The main canal of a gravity irrigation system is to be designed to carry a maximum discharge of 8 m^3/s. The cross sectional shape is to be trapezoidal with a side slope of 1:1. The bed is to be lined with concrete. The bottom slope is to be 0.0005. If the permissible b/d ratio is 3, the design depth should be ___.

a. 0.6 m

b. 0.8 m

c. 1.0 m

d. 1.2 m

PROBLEM 9: An unlined lateral canal is to be designed to irrigate 500 hectares. The bottom slope is to be 0.15% and the side slope z is 1.5. The roughness coefficient is 0.025. The maximum permissible velocity is 0.8 m/s. If the farm water requirement is 17.28 mm/day, the design bottom width should be ___.

a. 0.6 m

b. 0.85 m

c. 1.0 m

d. 1.25 m

PROBLEM 10: A 50m x 50 m furrow irrigation system was designed for the following conditions:

Soil water holding capacity = 180 mm/m

Rootzone depth = 300 mm

MAD = 50%

Application Efficiency = 70%

Furrow spacing = 75 cm

Fn =1.4 Tn^0.77

Assuming that the advance time is 1/3 of the net opportunity time, the inflow time should be

a. 22 min

b. 32 min

c. 42 min

d. 52 min