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The following step is to ensure that the cutoff time will have a practical value.
Running FURDEV in Mode 3 will generally give odd values for the resulting
cutoff time. Select Mode 4 ( M i n i m u m infiltrated depth) and change the cutoff
time from 620 to 600 min (= 10 hours). The minimum infiltrated depth slightly decreases from 100 to 97 mm and the application efficiency slightly increases from 71 to 73 % (Run 3 in Table 8.14). This is still an acceptable design.
The last step is to make sensitivity analyses on the field parameters used
in the design, ie, intake family, flow resistance and furrow shape. Runs 4 to 6
in Table 8.14 show that the variation in infiltration and flow resistance properties results in significantly different amounts of over-irrigation and corre-
Table 8.14 Results of design furrow length and sensitivity (file DESIGNS)
Run number
Calculation mode
1
2
2
3
3
4
4
4
5
4
6
4
7
4
1
-
1
350
1
350
1
350
-
600
600
600
100
0.04
0.008
0.75
1
100
0.04
0.008
0.75
1
1
350
600
100
0.04
0.008
0.75
1
1
350
-
1
350
600
100
0.04
0.008
0.75
1
100
0.04
0.008
0.75
1
100
0.08
0.008
0.75
1
100
0.04
0.008
0.75
2
-
-
-
-
-
-
-
0.6
0.6
0.6
0.6
0.7
0.6
0.6
OUTPUT PARAMETERS
Furrow length
Cutoff time
338
596
-
-
-
-
-
-
-
-
Application efficiency
Storage efficiency
Uniformity coefficient
Distribution uniformity
Deep percolation ratio
Surface runoff ratio
71
100
93
82
16
14
71
100
93
80
18
12
73
100
93
79
16
73
99
96
88
5
22
72
99
87
63
24
3
72
99
86
61
25
3
73
100
92
79
15
12
Minimum infiltrated depth
Maximum infiltrated depth
Average infiltrated depth
Over-irrigation depth
Under-irrigation depth
Over-irrigation length
Under-irrigation length
100
100
97
131
122
22
O
338
O
134
125
25
O
350
O
131
122
23
2
335
15
95
112
107
9
2
292
58
83
150
133
38
6
306
44
81
152
133
39
8
306
44
96
131
121
23
1
321
29
Advance time
Recession time
226
647
251
672
251
652
177
658
372
645
417
672
256
655
INPUT PARAMETERS
Flow rate
Furrow length
Cutoff time
Required depth
Flow resistance
Furrow slope
Furrow spacing
Side slope
Bed width
scs #
620
11
129