ACA SET EXAMINERS ANSWERS AND QUESTIONS
SET A+
✔✔An engineer is to design the mainline of a sprinkler system which will use a steel
(Scobey's coefficient K = 0.40) to carry a flow of 6.5 lps. The length of pipe is 150m and
the inside diameter is 100 mm. Compute the head loss of the system assuming a
uniform flow. - ✔✔Answer: 1.36 m
✔✔What is the evapotranspiration of corn during its growing period if the crop
coefficient is 2.5 and the reference crop evapotranspiration is 6 mm/day? - ✔✔Answer:
15 mm/day
✔✔The soil has a field capacity of 30.8% volume basis and a permanent wilting point of
12% dry mass basis. The apparent specific gravity is 1.4. If the rootzone depth is 1.0m
and the management allowable deficit is 50% the net application depth is. - ✔✔Answer:
70 mm
✔✔The capacity of a certain canal will be measured using a Cipolleti weir having a
length of 0.5m. If the height of the flowing water above the crest is 13 cm, what is the
well capacity in lps? - ✔✔Answer: 43.59
✔✔With this discharge, what will be the head above the crest if a V-notch is installed
somewhere along the same canal? - ✔✔Answer: 25 cm
✔✔Delivery of 360 cfs to an 80-acre field is continued for 4 hrs. Tail water flow is
estimated at 10 cfs. Soil probing after the irrigation indicates that 1 ft. of water was
stored in the rootzone. Compute the application efficiency. - ✔✔Answer: 67%
✔✔The duration of irrigation application for a 10ha cornfield for a given discharge of
100lps to obtain an average depth of application of 200mm assuming an application
efficiency of 70% should be. - ✔✔Answer: 8hrs
,✔✔How much water is needed in each irrigation if the moisture holding capacity of the
soil is 1.5 in/ft and irrigation was started when 40% is depleted. The crop uses 0.25
in/day of moisture and has a root depth of 3 ft. If there is no rain, how often will irrigation
be required? - ✔✔Answer: 1.8 in. every 7.2 days
✔✔Compute the water holding capacity of soil in inches if the F.C. is 30% and the
wilting point is 15% of the dry soil density. This density is 80 lbs/ft3 and the soil depth to
be irrigated is 2 feet. - ✔✔Answer: 4.6
✔✔The trapezoidal canal is to have a base width of 6 m and side slopes of 1:1. The
velocity of flow is 0.6 m/sec. What slope must be given the bed in order to deliver 5
m3/sec. Use Kutther's C, n=0.025. - ✔✔Answer: 0.000263
✔✔Given a probability of occurrence or exceedence of 5%. How many years will it take
before a discharge of 1000 m3/sec will be equaled or exceeded? - ✔✔Answer: 20
✔✔Given the following: bed slope = 0.0003 manning constant, n= 0.03 b/d ratio = 3.5
wetted perimeter = 14; z =0.5. The velocity of flow along a trapezoidal canal is? -
✔✔Answer: 0.82 m/s
✔✔A soil sample has wet mass of 120g and an undisturbed volume of 78cc. If the dry
mass basis moisture content is 20%, the bulk density is. - ✔✔Answer: 1.28g/cc
✔✔If the rectangular canal have base of 0.65 m, what would be the depth of flow when
the hydraulic radius is equal to the area of flow. - ✔✔Answer: 0.17 m
✔✔Given an irrigation depth of 30cm and 10 hrs of irrigation time, determine the
discharge needed to irrigate a hectare of land - ✔✔Answer: 300 cu.m/hr
✔✔One liter per second is equal to ___ gpm. - ✔✔Answer: 15.85
✔✔A farm channel carries a flow of 20 L/s for a field using furrow irrigation. If each
furrow required a flow of 1 L/s, how many furrow can be irrigated at a time? -
✔✔Answer: 20
✔✔An unlined trapezoidal irrigation canal is to carry a maximum discharge of 2,800lps.
The side slope is to be set at 1:1. The head loss over a 1km distance is 1m. The
Manning's roughness coefficient is 0.025. If the maximum permissible velocity is
0.92m/s, the design depth should be. - ✔✔Answer: 0.95m
✔✔An agricultural engineer uses the quarter time rules in irrigating the field. If the
contact time required to fill the soil reservoir is 1 day, how long will the water reach the
far end of the field - ✔✔Answer: 360 min
, ✔✔An average depth of 100mm of water is needed to irrigate 5 ha of land in 20 hrs,
what stream size is needed? - ✔✔Answer: 69.5 L/s
✔✔75mm of water is needed to irrigate the field. In order to irrigate adequately over the
whole area, an average depth of 100mm must be applied, how much water is lost 26 -
✔✔Answer: 25mm
✔✔75mm of water is needed to irrigate the field. In order to irrigate adequately over the
whole area, an average depth of 100mm must be applied, how much water is lost 26 -
✔✔Answer: 25mm
✔✔An 8 mm rainfall was measured by a USWB standard rain gauge, 8 inches in
diameter. Determines the depth in the inner cylinder whose area is 1/10 of the catch
area - ✔✔Answer: 80 mm
✔✔A 30inch diameter 1-meter long culvert has been designed to carry a maximum
discharge of 1.7m3/s when flowing half-full. Its roughness coefficient n is 0.014. If the
inlet and the outlet are both unsubmerged, the difference in elevation between the inlet
and the outlet should be. - ✔✔Answer: 10cm
✔✔Determine the 10 year period peak runoff for a 80ha watershed having a runoff
coefficient of 0.4, maximum length of water is 610m and the fall along this path is 6m.
The rainfall intensity for that return period is 101.25mm/hr having duration equal to the
time of concentration - ✔✔Answer: 9.0
✔✔The approximate threshold for the soil loss in the Philippines is around 12metric ton
per hectare per year. Assuming a soil bulk density of 1.2 metric ton / cu. m, What is the
soil erosion in mm/ yr. - ✔✔Answer: 1.0 mm / yr
✔✔The discharge in a triangular channel with a vertex angle of 90 degrees is 390lps.
The critical depth is. - ✔✔Answer: 0.5m
✔✔What is the erosion rate in 10 ha farm with an average slope of 3%. Given: slope
length factor =1.0, soil erodibility= 0.25, conservation practice factor =1.0 rainfall factor
=178 - ✔✔Answer: 26.7 mm / yr
✔✔A flood flow of 560 cu.m per second was determined to have a 20% probability of
occurrence. What is its return period? - ✔✔Answer: 5 years
✔✔For a watershed of 360 ha, the peak runoff rate for 0.5 cm/hr rain intensity (at the
time of concentration) was observed as 2.5 cu.m/s. What is the runoff coefficient? -
✔✔Answer: 0.05
SET A+
✔✔An engineer is to design the mainline of a sprinkler system which will use a steel
(Scobey's coefficient K = 0.40) to carry a flow of 6.5 lps. The length of pipe is 150m and
the inside diameter is 100 mm. Compute the head loss of the system assuming a
uniform flow. - ✔✔Answer: 1.36 m
✔✔What is the evapotranspiration of corn during its growing period if the crop
coefficient is 2.5 and the reference crop evapotranspiration is 6 mm/day? - ✔✔Answer:
15 mm/day
✔✔The soil has a field capacity of 30.8% volume basis and a permanent wilting point of
12% dry mass basis. The apparent specific gravity is 1.4. If the rootzone depth is 1.0m
and the management allowable deficit is 50% the net application depth is. - ✔✔Answer:
70 mm
✔✔The capacity of a certain canal will be measured using a Cipolleti weir having a
length of 0.5m. If the height of the flowing water above the crest is 13 cm, what is the
well capacity in lps? - ✔✔Answer: 43.59
✔✔With this discharge, what will be the head above the crest if a V-notch is installed
somewhere along the same canal? - ✔✔Answer: 25 cm
✔✔Delivery of 360 cfs to an 80-acre field is continued for 4 hrs. Tail water flow is
estimated at 10 cfs. Soil probing after the irrigation indicates that 1 ft. of water was
stored in the rootzone. Compute the application efficiency. - ✔✔Answer: 67%
✔✔The duration of irrigation application for a 10ha cornfield for a given discharge of
100lps to obtain an average depth of application of 200mm assuming an application
efficiency of 70% should be. - ✔✔Answer: 8hrs
,✔✔How much water is needed in each irrigation if the moisture holding capacity of the
soil is 1.5 in/ft and irrigation was started when 40% is depleted. The crop uses 0.25
in/day of moisture and has a root depth of 3 ft. If there is no rain, how often will irrigation
be required? - ✔✔Answer: 1.8 in. every 7.2 days
✔✔Compute the water holding capacity of soil in inches if the F.C. is 30% and the
wilting point is 15% of the dry soil density. This density is 80 lbs/ft3 and the soil depth to
be irrigated is 2 feet. - ✔✔Answer: 4.6
✔✔The trapezoidal canal is to have a base width of 6 m and side slopes of 1:1. The
velocity of flow is 0.6 m/sec. What slope must be given the bed in order to deliver 5
m3/sec. Use Kutther's C, n=0.025. - ✔✔Answer: 0.000263
✔✔Given a probability of occurrence or exceedence of 5%. How many years will it take
before a discharge of 1000 m3/sec will be equaled or exceeded? - ✔✔Answer: 20
✔✔Given the following: bed slope = 0.0003 manning constant, n= 0.03 b/d ratio = 3.5
wetted perimeter = 14; z =0.5. The velocity of flow along a trapezoidal canal is? -
✔✔Answer: 0.82 m/s
✔✔A soil sample has wet mass of 120g and an undisturbed volume of 78cc. If the dry
mass basis moisture content is 20%, the bulk density is. - ✔✔Answer: 1.28g/cc
✔✔If the rectangular canal have base of 0.65 m, what would be the depth of flow when
the hydraulic radius is equal to the area of flow. - ✔✔Answer: 0.17 m
✔✔Given an irrigation depth of 30cm and 10 hrs of irrigation time, determine the
discharge needed to irrigate a hectare of land - ✔✔Answer: 300 cu.m/hr
✔✔One liter per second is equal to ___ gpm. - ✔✔Answer: 15.85
✔✔A farm channel carries a flow of 20 L/s for a field using furrow irrigation. If each
furrow required a flow of 1 L/s, how many furrow can be irrigated at a time? -
✔✔Answer: 20
✔✔An unlined trapezoidal irrigation canal is to carry a maximum discharge of 2,800lps.
The side slope is to be set at 1:1. The head loss over a 1km distance is 1m. The
Manning's roughness coefficient is 0.025. If the maximum permissible velocity is
0.92m/s, the design depth should be. - ✔✔Answer: 0.95m
✔✔An agricultural engineer uses the quarter time rules in irrigating the field. If the
contact time required to fill the soil reservoir is 1 day, how long will the water reach the
far end of the field - ✔✔Answer: 360 min
, ✔✔An average depth of 100mm of water is needed to irrigate 5 ha of land in 20 hrs,
what stream size is needed? - ✔✔Answer: 69.5 L/s
✔✔75mm of water is needed to irrigate the field. In order to irrigate adequately over the
whole area, an average depth of 100mm must be applied, how much water is lost 26 -
✔✔Answer: 25mm
✔✔75mm of water is needed to irrigate the field. In order to irrigate adequately over the
whole area, an average depth of 100mm must be applied, how much water is lost 26 -
✔✔Answer: 25mm
✔✔An 8 mm rainfall was measured by a USWB standard rain gauge, 8 inches in
diameter. Determines the depth in the inner cylinder whose area is 1/10 of the catch
area - ✔✔Answer: 80 mm
✔✔A 30inch diameter 1-meter long culvert has been designed to carry a maximum
discharge of 1.7m3/s when flowing half-full. Its roughness coefficient n is 0.014. If the
inlet and the outlet are both unsubmerged, the difference in elevation between the inlet
and the outlet should be. - ✔✔Answer: 10cm
✔✔Determine the 10 year period peak runoff for a 80ha watershed having a runoff
coefficient of 0.4, maximum length of water is 610m and the fall along this path is 6m.
The rainfall intensity for that return period is 101.25mm/hr having duration equal to the
time of concentration - ✔✔Answer: 9.0
✔✔The approximate threshold for the soil loss in the Philippines is around 12metric ton
per hectare per year. Assuming a soil bulk density of 1.2 metric ton / cu. m, What is the
soil erosion in mm/ yr. - ✔✔Answer: 1.0 mm / yr
✔✔The discharge in a triangular channel with a vertex angle of 90 degrees is 390lps.
The critical depth is. - ✔✔Answer: 0.5m
✔✔What is the erosion rate in 10 ha farm with an average slope of 3%. Given: slope
length factor =1.0, soil erodibility= 0.25, conservation practice factor =1.0 rainfall factor
=178 - ✔✔Answer: 26.7 mm / yr
✔✔A flood flow of 560 cu.m per second was determined to have a 20% probability of
occurrence. What is its return period? - ✔✔Answer: 5 years
✔✔For a watershed of 360 ha, the peak runoff rate for 0.5 cm/hr rain intensity (at the
time of concentration) was observed as 2.5 cu.m/s. What is the runoff coefficient? -
✔✔Answer: 0.05
