ACA Exam QUESTIONS AND CORRECT
ANSWERS
The recent monsoon rains have posted a nearly uniform rainfall intensity of 30 mm/hr over a 1,500-
hectare watershed area in Central Luzon. If the runoff coefficient is 0.15, what is the runoff in
m3/sec? - CORRECT ANSWER Answer: 18.75
A television network is planning to air four 30-minute sitcoms namely: "Mana-Mana", "Okidoki",
"Tanging Ama" and "Home Along da Sea". In how many ways can the network arrange these sitcoms
in a 7-9 pm time slot if "Mana-Mana" should be aired third? - CORRECT ANSWER Answer:
6
An artesian well has a diameter of 10 cm. Under steady state condition, what is the expected discharge
(lps) if the drawdown is 2.5 m and the radius of influence is 120 m? The aquifer's hydraulic
conductivity and thickness are 75 m/day and 4 m, respectively. - CORRECT ANSWER
Answer: 7.01 lps
What is the soil erosion of 10 T/ha/yr in mm/yr? Assume that the soil bulk density is 1.2 T/m3. -
CORRECT ANSWER Answer: 0.83 mm/yr
The gross application depth is 93mm to irrigate a crop with a crop coefficient of 0.9. The reference
crop evapotranspiration is 6mm/day. If the application efficiency is 70%, the irrigation interval is -
CORRECT ANSWER Answer: 12days
The discharge of first emitter in a dropper line is 12 lph. What is the allowable minimum discharge in
the last emitter? - CORRECT ANSWER Answer: 9.6 lph
What is the depth of flowing water in a trapezoidal canal with a side slope of 1:1 and base of 1.0 m if
the stream velocity is 1 mps and the average discharge is 6 cms. - CORRECT ANSWER
Answer: 2.0 m
The soil has a field capacity and permanent wilting point of 27% and 13%, respectively. What is the
readily available moisture in cm of water per cm of soil if the bulk density is 1.25 g/cc? - CORRECT
ANSWER Answer: 13.12 cm/m
,What discharge can be expected from an unconfined well 200 mm in diameter if the drawdown is 5 m
in an aquifer saturated to a depth of 18 m? Assume the permeability and the radius of influence to be
20 m/day and 150 m, respectively. - CORRECT ANSWER Answer: 15.4 lps
The hydraulic radius of a pipe with a diameter of 12 mm. - CORRECT ANSWER Answer:
3mm
In an attempt to the groundwater flow of a certain farm, two parallel canals have to be constructed. It
was observed that the impervious layer exist at a depth of 1.9 m below the soil surface and the soil has
a k value of 1.2 m/day. If the water table has to be maintained at a depth of 0.8 m below the soil
surface, what will be the spacing of the drain when the drain level is 1.5 m below the soil. Assume a
steady recharge of 2 mm/day. - CORRECT ANSWER Answer: 50.20 m
A discharge of 20 lps is equivalent to ___ m3/hr: - CORRECT ANSWER Answer: 72 m3/hr
Given an irrigation depth of 30 cm and 10 hrs of irrigation time. Determine the discharge to irrigate a
hectare of land. - CORRECT ANSWER Answer: 300 m3/hr
Given bed slope=0.0003; Manning's coefficient, n=0.03; b/d ratio=3.5; wetted perimeter, p=14; z=0.5.
The velocity of flow along a trapezoidal canal is: - CORRECT ANSWER Answer: 0.89 m/s
The thickness of a confined aquifer is 5 m, well diameter=40 cm, radius of influence=250 m, k=10
m/day, height of water in the pumping well=1,325 m, height of piezometric surface=1,500 m. The
steady state discharge is: - CORRECT ANSWER Answer: 0.089 m3/sec
How many sprinklers with spacing of 7m x 7m are needed to irrigate a rectangular field of 150m x
200m if the laterals are set parallel to the larger side of the field: - CORRECT ANSWER
Answer: 588
If the theoretical flow of velocity in an orifice is 4 m/s, what is the height of water flowing above the
center of the orifice? - CORRECT ANSWER Answer: 0.8m
Given an irrigation depth of 30 cm and 8 hrs of irrigation time. Determine the discharge needed to
irrigate a hectare of land: - CORRECT ANSWER Answer: 375 m3/hr
, A flood flow of 560 m3/s was determined to have a 50% probability of occurrence. What is its return
period? - CORRECT ANSWER Answer: 20 years
A farmer is to irrigate a crop planted in furrows of 100m x 100m area. His furrow spacing is 50 cm
and the application depth is 100 mm. If the inflow rate is 0.4 lps/100m, determine the time of
irrigating each furrow: - CORRECT ANSWER Answer: 3.47 hrs
The operating pressure of the sprinkler heads in a sprinkler irrigation system is 12.52 kg/cm2. What is
the allowable pressure (kg/m2) variation between the first and the last sprinkler head in a lateral? -
CORRECT ANSWER Answer: 2.504
A rectangular water tank, 2 meters high, is filled with water. Due to rust, a circular hole was made on
lowest portion of one side of the tank. Considering that the tank is maintained full, what is the
velocity of water right after its take-off from the hole? - CORRECT ANSWER Answer: 39.22
m/s
If the speed of an irrigation centrifugal pump is increased by 30%, the power requirement is increased
by: - CORRECT ANSWER Answer: 2.197
A farmer proposes to use sprinkler on a rectangular field 160m x 120m with lateral line parallel to the
shorter side. The land is adjacent to the river from which he pumps water. He needs a maximum
application depth of 60 mm every 10 days. The maximum intake rate of the soil is 8.5 mm/hr and the
application efficiency is 80%. Sprinkler spacing is 9m x 9m. What is the desired discharge per
sprinkler in lps? - CORRECT ANSWER Answer: 0.19125 lps
What should be the diameter of a pipe such that the two of them will be just sufficient to hold the
water in an open canal 2m wide and 1m deep? Assume half square section canal and use a common
slope of 0.0007 and Chezy's coefficient = 58. - CORRECT ANSWER Answer: 1m
The following depths of water penetration in meters were observed at 10m interval along a furrow
irrigation system:0.65, 0.66, 0.68,0.72, 0.73, 0.77, 0.78, 0.80, 0.82, and 0.86. The uniformity
coefficient is. - CORRECT ANSWER Answer: 92%
Given the soil sampler with a diameter of 5.2 cm and length of 4.7 cm. What is the bulk volume of
soil it could gather? - CORRECT ANSWER Answer: 100 cc
ANSWERS
The recent monsoon rains have posted a nearly uniform rainfall intensity of 30 mm/hr over a 1,500-
hectare watershed area in Central Luzon. If the runoff coefficient is 0.15, what is the runoff in
m3/sec? - CORRECT ANSWER Answer: 18.75
A television network is planning to air four 30-minute sitcoms namely: "Mana-Mana", "Okidoki",
"Tanging Ama" and "Home Along da Sea". In how many ways can the network arrange these sitcoms
in a 7-9 pm time slot if "Mana-Mana" should be aired third? - CORRECT ANSWER Answer:
6
An artesian well has a diameter of 10 cm. Under steady state condition, what is the expected discharge
(lps) if the drawdown is 2.5 m and the radius of influence is 120 m? The aquifer's hydraulic
conductivity and thickness are 75 m/day and 4 m, respectively. - CORRECT ANSWER
Answer: 7.01 lps
What is the soil erosion of 10 T/ha/yr in mm/yr? Assume that the soil bulk density is 1.2 T/m3. -
CORRECT ANSWER Answer: 0.83 mm/yr
The gross application depth is 93mm to irrigate a crop with a crop coefficient of 0.9. The reference
crop evapotranspiration is 6mm/day. If the application efficiency is 70%, the irrigation interval is -
CORRECT ANSWER Answer: 12days
The discharge of first emitter in a dropper line is 12 lph. What is the allowable minimum discharge in
the last emitter? - CORRECT ANSWER Answer: 9.6 lph
What is the depth of flowing water in a trapezoidal canal with a side slope of 1:1 and base of 1.0 m if
the stream velocity is 1 mps and the average discharge is 6 cms. - CORRECT ANSWER
Answer: 2.0 m
The soil has a field capacity and permanent wilting point of 27% and 13%, respectively. What is the
readily available moisture in cm of water per cm of soil if the bulk density is 1.25 g/cc? - CORRECT
ANSWER Answer: 13.12 cm/m
,What discharge can be expected from an unconfined well 200 mm in diameter if the drawdown is 5 m
in an aquifer saturated to a depth of 18 m? Assume the permeability and the radius of influence to be
20 m/day and 150 m, respectively. - CORRECT ANSWER Answer: 15.4 lps
The hydraulic radius of a pipe with a diameter of 12 mm. - CORRECT ANSWER Answer:
3mm
In an attempt to the groundwater flow of a certain farm, two parallel canals have to be constructed. It
was observed that the impervious layer exist at a depth of 1.9 m below the soil surface and the soil has
a k value of 1.2 m/day. If the water table has to be maintained at a depth of 0.8 m below the soil
surface, what will be the spacing of the drain when the drain level is 1.5 m below the soil. Assume a
steady recharge of 2 mm/day. - CORRECT ANSWER Answer: 50.20 m
A discharge of 20 lps is equivalent to ___ m3/hr: - CORRECT ANSWER Answer: 72 m3/hr
Given an irrigation depth of 30 cm and 10 hrs of irrigation time. Determine the discharge to irrigate a
hectare of land. - CORRECT ANSWER Answer: 300 m3/hr
Given bed slope=0.0003; Manning's coefficient, n=0.03; b/d ratio=3.5; wetted perimeter, p=14; z=0.5.
The velocity of flow along a trapezoidal canal is: - CORRECT ANSWER Answer: 0.89 m/s
The thickness of a confined aquifer is 5 m, well diameter=40 cm, radius of influence=250 m, k=10
m/day, height of water in the pumping well=1,325 m, height of piezometric surface=1,500 m. The
steady state discharge is: - CORRECT ANSWER Answer: 0.089 m3/sec
How many sprinklers with spacing of 7m x 7m are needed to irrigate a rectangular field of 150m x
200m if the laterals are set parallel to the larger side of the field: - CORRECT ANSWER
Answer: 588
If the theoretical flow of velocity in an orifice is 4 m/s, what is the height of water flowing above the
center of the orifice? - CORRECT ANSWER Answer: 0.8m
Given an irrigation depth of 30 cm and 8 hrs of irrigation time. Determine the discharge needed to
irrigate a hectare of land: - CORRECT ANSWER Answer: 375 m3/hr
, A flood flow of 560 m3/s was determined to have a 50% probability of occurrence. What is its return
period? - CORRECT ANSWER Answer: 20 years
A farmer is to irrigate a crop planted in furrows of 100m x 100m area. His furrow spacing is 50 cm
and the application depth is 100 mm. If the inflow rate is 0.4 lps/100m, determine the time of
irrigating each furrow: - CORRECT ANSWER Answer: 3.47 hrs
The operating pressure of the sprinkler heads in a sprinkler irrigation system is 12.52 kg/cm2. What is
the allowable pressure (kg/m2) variation between the first and the last sprinkler head in a lateral? -
CORRECT ANSWER Answer: 2.504
A rectangular water tank, 2 meters high, is filled with water. Due to rust, a circular hole was made on
lowest portion of one side of the tank. Considering that the tank is maintained full, what is the
velocity of water right after its take-off from the hole? - CORRECT ANSWER Answer: 39.22
m/s
If the speed of an irrigation centrifugal pump is increased by 30%, the power requirement is increased
by: - CORRECT ANSWER Answer: 2.197
A farmer proposes to use sprinkler on a rectangular field 160m x 120m with lateral line parallel to the
shorter side. The land is adjacent to the river from which he pumps water. He needs a maximum
application depth of 60 mm every 10 days. The maximum intake rate of the soil is 8.5 mm/hr and the
application efficiency is 80%. Sprinkler spacing is 9m x 9m. What is the desired discharge per
sprinkler in lps? - CORRECT ANSWER Answer: 0.19125 lps
What should be the diameter of a pipe such that the two of them will be just sufficient to hold the
water in an open canal 2m wide and 1m deep? Assume half square section canal and use a common
slope of 0.0007 and Chezy's coefficient = 58. - CORRECT ANSWER Answer: 1m
The following depths of water penetration in meters were observed at 10m interval along a furrow
irrigation system:0.65, 0.66, 0.68,0.72, 0.73, 0.77, 0.78, 0.80, 0.82, and 0.86. The uniformity
coefficient is. - CORRECT ANSWER Answer: 92%
Given the soil sampler with a diameter of 5.2 cm and length of 4.7 cm. What is the bulk volume of
soil it could gather? - CORRECT ANSWER Answer: 100 cc
