BRAE 340 Problem set 1 Essay

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a. Power– kilowatt,
b. Area – acres,
c. Application Rate – in/hr,
d. Pressure – head,
e. Depth – inches,
f. Length – miles,
g. Velocity – ft/sec,
h. Volume – ac-in,
i. Flow Rate – cu-ft/sec
2. Statements (1) and (2) refer to water volumes. Are these Net or Gross volumes? (1) Crop water use (cu-ft) = Seasonal ET (ft) x Crop area (acres) x 43,560 sq-ft/acre (2) Volume applied by system (ac-in) = Application rate (in/hr) x Irrigation time (hr) x Area (acres)
a. (1) is Net; (2) is Gross
b. (1) is Gross; (2) is Gross
c. (1) is Gross; (2) is Net
d. (1) is Net; (2) is Net
3. Statements (1) and (2) refer to water amounts. Are these Net or Gross amounts? (1) Crop water
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A salt concentration of 1562 ppm is equivalent to an electrical conductivity of how many dS/m?
a. 1 dS/m ≈ 700 ppm
b. ppm x (1 dS/m)/(700 ppm) = dS/m
c. The correct answer is: 2.2314285714286
13. If a soil has a moisture tension of 0.15 bars and the salinity of the soil water is 1.86 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?
a. 57 cb
b. 34 cb
c. 71 cb
d. 67 cb
e. 206 cb
i. moisture tension = bars x 100 cb/bar = cb ii. osmotic tension = dS/m x 30 cb/(1 dS/m) = cb iii. total tension = moisture tension (cb) + osmotic tension (cb)
14. What pumping rate (CFS) is required to deliver 47 acre-inches in 20 hours?
a. rate = amount ÷ time
b. rate = ac-in/hr x 1 CFS/1 ac-in/hr = CFS
c. The correct answer is: 2.35
15. Crop ET is 0.22 in/day, and irrigations are every 7 days. What is the crop water use between irrigations (in)?
a. Amount = rate (in/day) x time (days) = inches
b. The correct answer is: 1.54
16. 30 acres of cotton uses water at the rate of 0.21 inches per day. How many cubic feet per day does the cotton use?
a. Volume = depth (in) x area (acres) = ac-in/day
b. ac-in/day x 1 ft/12 in x 43560 sq-ft/acre = cu-ft/day
c. The correct answer is: 22869
17. A rain gauge is constructed of a funnel with diameter D = 4 inches, fixed to the top of a tube with diameter d = 2 inches (see drawing). Rain water

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