BRAE 340 Exam 1 Questions and Answers
100% Solved
An elevated water tank is used to feed water into a drip system. How high (ft) must the tank
outlet be in order to cause a 31 psi pressure at the inlet of the drip system? Correct Answ_psi
x 2.31 ft/psi = ft
The correct answer is: 71.6
What concentration (ppm) is equivalent to a soil moisture tension of 1.5 bars? Correct
Answ_bars x 100 = cb
cb x 1dS/m/30 cb = dS/m
dS/m x 700 ppm/1 dS/m = ppm
The correct answer is: 3500
What salinity (ds/m) is equivalent to a soil moisture tension of 0.34 bars? Correct Answ_1
bar = 100 centibars (cb); 1 dS/m ≈ 30 cb
bars x 100 = cb x 1 dS/m/30 cb = dS/m
The correct answer is: 1.13 dS/m
,If a soil has a moisture tension of 0.17 bars and the salinity of the soil water is 1.48 dS/m, what is
the total tension experienced by the plant roots? That is, what is the sum of the moisture tension
and the osmotic (due to salinity) tension? Correct Answ_moisture tension = bars x 100
cb/bar = cb
osmotic tension = dS/m x 30 cb/(1 dS/m) = cb
total tension = moisture tension (cb) + osmotic tension (cb)
The correct answer is: 61 cb
What pumping rate (CFS) is required to deliver 63 acre-inches in 20 hours? Correct
Answ_rate = amount ÷ time
rate = ac-in/hr x 1 CFS/1 ac-in/hr = CFS
The correct answer is: 3.15
An alfalfa crop uses 0.38 inches per day. How many days will it take to extract 4.42 inches from
the soil? Correct Answ_Time = amount (in)/ rate (in/day) = days
The correct answer is: 11.6
What is the average depth applied (inches) to a 9 acre level basin if the irrigation pump runs at 11
CFS for 4 hours? Correct Answ_1 CFS ≈ 1 ac-in/hr
, ac-in/hr x hours = ac-in
ac-in ÷ acre = inches
The correct answer is: 4.89
A rain gauge is constructed of a funnel with diameter D = 4 inches, fixed to the top of a tube with
diameter d = 1 inches (see drawing). Rain water stands 3.38 inches high in the bottom of the
tube. How much rainfall does that indicate? Correct Answ_Volume in tube = column x tube
area
Tube area = ∏ d2/4 = sq-in
Volume in tube = rainfall (in) x tube area = cu-in
Rain depth = volume in tube (cu-in) ÷ top funnel area (sq-in)
The correct answer is: 0.21 inches
A pump delivers a gross flow rate of 2.7 CFS to a 9 acre field for 9 hours. The irrigation
efficiency is 74%. What is the net amount of water benefiting the crop? Correct Answ_CFS x
60 sec/1 min x 60 min/1 hr = cu-ft/hr
cu-ft/hr x hours x 1 ac/43560 sq-ft = ac-ft
ac-ft / acres x 12 in/ft = inches gross (this is a gross amount because it is coming from the pump)
Net = Gross (in) x (IE/100) = inches net
100% Solved
An elevated water tank is used to feed water into a drip system. How high (ft) must the tank
outlet be in order to cause a 31 psi pressure at the inlet of the drip system? Correct Answ_psi
x 2.31 ft/psi = ft
The correct answer is: 71.6
What concentration (ppm) is equivalent to a soil moisture tension of 1.5 bars? Correct
Answ_bars x 100 = cb
cb x 1dS/m/30 cb = dS/m
dS/m x 700 ppm/1 dS/m = ppm
The correct answer is: 3500
What salinity (ds/m) is equivalent to a soil moisture tension of 0.34 bars? Correct Answ_1
bar = 100 centibars (cb); 1 dS/m ≈ 30 cb
bars x 100 = cb x 1 dS/m/30 cb = dS/m
The correct answer is: 1.13 dS/m
,If a soil has a moisture tension of 0.17 bars and the salinity of the soil water is 1.48 dS/m, what is
the total tension experienced by the plant roots? That is, what is the sum of the moisture tension
and the osmotic (due to salinity) tension? Correct Answ_moisture tension = bars x 100
cb/bar = cb
osmotic tension = dS/m x 30 cb/(1 dS/m) = cb
total tension = moisture tension (cb) + osmotic tension (cb)
The correct answer is: 61 cb
What pumping rate (CFS) is required to deliver 63 acre-inches in 20 hours? Correct
Answ_rate = amount ÷ time
rate = ac-in/hr x 1 CFS/1 ac-in/hr = CFS
The correct answer is: 3.15
An alfalfa crop uses 0.38 inches per day. How many days will it take to extract 4.42 inches from
the soil? Correct Answ_Time = amount (in)/ rate (in/day) = days
The correct answer is: 11.6
What is the average depth applied (inches) to a 9 acre level basin if the irrigation pump runs at 11
CFS for 4 hours? Correct Answ_1 CFS ≈ 1 ac-in/hr
, ac-in/hr x hours = ac-in
ac-in ÷ acre = inches
The correct answer is: 4.89
A rain gauge is constructed of a funnel with diameter D = 4 inches, fixed to the top of a tube with
diameter d = 1 inches (see drawing). Rain water stands 3.38 inches high in the bottom of the
tube. How much rainfall does that indicate? Correct Answ_Volume in tube = column x tube
area
Tube area = ∏ d2/4 = sq-in
Volume in tube = rainfall (in) x tube area = cu-in
Rain depth = volume in tube (cu-in) ÷ top funnel area (sq-in)
The correct answer is: 0.21 inches
A pump delivers a gross flow rate of 2.7 CFS to a 9 acre field for 9 hours. The irrigation
efficiency is 74%. What is the net amount of water benefiting the crop? Correct Answ_CFS x
60 sec/1 min x 60 min/1 hr = cu-ft/hr
cu-ft/hr x hours x 1 ac/43560 sq-ft = ac-ft
ac-ft / acres x 12 in/ft = inches gross (this is a gross amount because it is coming from the pump)
Net = Gross (in) x (IE/100) = inches net
