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BRAE 340 Irrig. Water Management
Name:
HW 1  Terms, Units and Relationships
(only odd numbered problems will be graded)
Prob. 112:
Matching.
Determine whether each of these is a beneficial or nonbeneficial use of water.
N) Nonbeneficial use of water
B) Beneficial use of water
[B]
1.
Iceencasement frost protection
[B]
2.
Maintenance of plant habitat for beneficial insects
[N]
3.
Uncollected runoff
[B]
4.
Crop evapotranspiration, ETc
[N]
5.
Weed ET
[B]
6.
Soil crust softening (for better crop germination)
[B]
7.
Salt removal, leaching
[N]
8.
Canal seepage
[B]
9.
Water born application of fertilizers/chemicals, fertigation/chemigation
[N] 10. Drift or overthrow outside cropped area
[N] 11. Evaporation from canals
[N] 12. Evaporation from reservoirs
[A] 13. Given:
An irrigation system applies a gross amount of 43 inches of water during the growing
seaason.
An evaluation determines that: 29 inches goes to satisfy crop ET; 8 inches runs off
and is not collected for reuse; 5 inches passes through the root zone as deep percolation
(total deep percolation), of which 1 inch is beneficial leaching for salt removal; and 1 inch
is ET from weeds. What is the amount of irrrigation water beneficially used (inches)?
A) 30 inches
B) 22 inches
C) 26 inches
D) 34 inches
E) 40 inches
Solution:
Beneficial uses => crop ET + leaching = 29 + 1 = 30 inches
[D] 14. An irrigation system applies a gross amount of 39 inches of water during a growing season.
An
evaluation determines the following ; 27 inches goes to satisfy crop ET; there is no runoff; 4 inches is
used for crop cooling; 6 inches passes through the root zone as deep percolation (total deep
percolation), of which 3 inches are beneficial leaching for salt removal; and 2 inches goes to weed ET
and overthrow onto noncropped land.
How much irrigation water goes to nonbeneficial uses (in)?
A) 3.9 inches
B) 2.9 inches
C) 2.4 inches
D) 5.0 inches
E) 1.7 inches
Solution:
NonBeneficial = excess deep percolation + weed ET
excess deep pecolation = total DP  beneficial DP for leaching = 6
 3 = 3 inches
nonbeneficial = 3 + 2 = 5.0 inches
[C] 15. Statements (X) and (Y) refer to water requirements.
Are these Net or Gross requirements?
(X) The drip system must deliver 48 gallons per tree per day.
(Y) This vine requires up to 8 gallons of water per day.
A) (X) is Net;
(Y) is Gross
B) (X) is Gross;
(Y) is Gross
C) (X) is Gross;
(Y) is Net
D) (X) is Net;
(Y) is Net
Explanation
[X] refers to the Pump or System => this is a Gross amount
[Y] refers to the Crop => this is a Net amount
Solution Key
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View Full Document[B] 16. Statements (K) and (L) refer to water volumes.
Are these Net or Gross volumes?
(K) Plant water use (gal) = Plant area (sqft) x Plant water use (in) ÷ 12 in/ft x 7.48 gal/cuft
(L) Volume pumped (gal) = Pumping rate (gpm) x Pumping time (minutes)
A) (K) is Net;
(L) is Net
B) (K) is Net;
(L) is Gross
C) (K) is Gross;
(L) is Net
D) (K) is Gross;
(L) is Gross
Explanation
[K] refers to the Crop => this is a Net amount
[L] refers to the Pump or System => this is a Gross amount
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 Fall '09
 burgoa

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