Tabel 4.16 Analisa Kebutuhan Air Irigasi Untuk Alternatif-12
Pola tanam : Padi - Padi - Palawija
Periode Tanam : Padi – I
Oktober 1 : Padi - II Februari 1
: Palawija Juni 1 Bulan
Re Eto
P WLR
Koefisien Tanaman Etc
NFR DR
mmhari mmhari
mmhari mmhari
C1 C2
C3 C
mmhari mmhari
ltrdtkha 1
2 3
4 5
6 7
8 9
10 11
12.00 jan
I 3.18
4.53 2.00
1.10 0.95
1.05 0.67
3.02 2.94
0.52 II
2.74 4.53
2.00 1.10
0.95 0.32
1.43 1.80
0.32 Feb
I 1.51
5.06 2.00
0.00 0.00
0.49 0.09
II 1.42
5.06 2.00
LP LP
LP LP
11.14 9.72
1.73 Mar
I 1.02
4.99 2.00
1.10 LP
LP LP
11.09 10.07
1.79 II
2.39 4.99
2.00 1.10
1.10 LP
LP 11.09
8.70 1.55
Apr I
2.76 4.41
2.00 1.10
1.05 1.10
1.10 1.08
4.78 5.12
0.91 II
1.81 4.41
2.00 1.10
1.05 1.05
1.10 1.07
4.71 6.00
1.07 Mei
I 4.60
4.22 2.00
2.20 0.95
1.05 1.05
1.02 4.29
3.90 0.69
II 3.19
4.22 2.00
1.10 0.95
1.05 0.67
2.82 2.73
0.49 Juni
I 3.69
4.19 2.00
1.10 0.50
0.95 0.48
2.03 1.44
0.26 II
2.68 4.19
2.00 0.75
0.50 0.42
1.75 1.07
0.19 Juli
I 2.54
4.31 2.00
1.00 0.75
0.50 0.75
3.23 2.69
0.48 II
3.80 4.31
2.00 1.00
1.00 0.75
0.92 3.95
2.15 0.38
Ags I
2.66 4.79
2.00 0.82
1.00 1.00
0.94 4.50
3.84 0.68
II 4.60
4.79 2.00
0.45 0.82
1.00 0.76
3.62 1.03
0.18 Sep
I 5.93
4.88 2.00
0.45 0.82
0.42 2.07
0.00 0.00
II 7.53
4.88 2.00
0.45 0.15
0.73 0.00
0.00 Okt
I 5.03
4.61 2.00
LP LP
LP LP
5.58 0.54
0.10 II
7.15 4.61
2.00 1.10
LP LP
LP 5.58
0.00 0.00
Nop I
4.18 4.34
2.00 1.10
1.10 LP
LP 10.62
6.44 1.15
II 5.96
4.34 2.00
1.10 1.05
1.10 1.10
1.08 4.70
1.84 0.33
Des I
3.82 4.34
2.00 1.10
1.05 1.05
1.10 1.07
4.63 3.91
0.70 II
3.16 4.34
2.00 2.20
0.95 1.05
1.05 1.02
4.41 5.46
0.97
Kebutuhan Air Maksimum Padi I
6.44 1.15
Padi II 10.07
1.79 Palawija
3.84 0.68
Sumber : Hasil Perhitungan
Universitas Sumatera Utara
Analisa kebutuhan air irigasi pada tabel 4.5 diperoleh dengan menggunakan perhitungan sebagai berikut :
Direncanakan waktu penyiapan sawah T 1,5 bulan S = 300 mm Pola tanam
: Padi-Padi-Palawija Periode Tanam : Padi-I Nopember 1, Padi-II Maret 1, Palawija Juli 1.
a. Nopember 1
M = 1,1 x Eto + P
= 1,1 x 4,34 + 2,00 = 6,77
mm hari
Dari tabel 2.8 didapat LP = Etc = 10,62 interpolasi NFR = LP – Re
= 10,62 – 4,18 = 6,44
mm hari
Ef = 65 diporeleh dari 90 x 90 x 80 = 64,8 ≈ 65
Dr =
ef x 8, 64 NFR
=
6, 44 0,65 x 8, 64
= 1,15 ltrdtkHa b.
Nopember 2 M
= 1,1 x Eto + P = 1,1 x 4,34 + 2,00
= 6,77
mm hari
NFR = LP – Re
Universitas Sumatera Utara
= 10,62 – 5,96 = 4,66
mm hari
Dr =
ef x 8, 64 NFR
=
4, 66 0,65 x 8, 64
= 0,83 ltrdtkHa c.
Desember 1 M
= 1,1 x Eto + P = 1,1 x 4,34 + 2,00
= 6,77
mm hari
NFR = LP – Re = 10,62 – 3,82
= 6,80
mm hari
Dr =
ef x 8, 64 NFR
=
6,80 0,65 x 8, 64
= 1,21 ltrdtkHa d.
Desember 2 C
=
1 2
3
C C
C 3
+ +
= 1, 05 1,10 1,10
3 +
+
= 1,08
Universitas Sumatera Utara
Etc = ETo x C = 4,34 x 1,08
= 4,70
mm hari
NFR = Etc + P - Re + WLR = 4,70 + 2,00 – 3,16 + 1,10
= 4.64
mm hari
Dr =
ef x 8, 64 NFR
=
4, 64 0,65 x 8, 64
=
0,83 ltrdtkHa e.
Januari 1 C
=
1 2
3
C C
C 3
+ +
= 1, 05 1, 05 1,10
3 +
+
= 1,07 Etc = ETo x C
= 4,53 x 1,07 = 4,83
mm hari
NFR = Etc + P - Re + WLR = 4,83 + 2,00 – 3,18 + 1,10
= 4,75
mm hari
Dr =
ef x 8, 64 NFR
Universitas Sumatera Utara
=
4, 75 0,65 x 8, 64
=
0,85 ltrdtkHa
f. Januari 2
C =
1 2
3
C C
C 3
+ +
= 0, 95 1, 05 1, 05
3 +
+
= 1,02 Etc = ETo x C
= 4,53 x 1,02 = 4,60
mm hari
NFR = Etc + P - Re + WLR = 4,60 + 2,00 – 2,74 + 2,20
= 6,07
mm hari
Dr =
ef x 8, 64 NFR
=
6, 07 0,65 x 8, 64
=
1,08 ltrdtkHa g.
Februari 1 C
=
1 2
3
C C
C 3
+ +
Universitas Sumatera Utara
= 0 0, 95 1, 05
3 +
+
= 0,67 Etc = ETo x C
= 5,06 x 0,67 = 3,38
mm hari
NFR = Etc + P - Re + WLR = 3,38 + 2,00 – 1,51 + 1,10
= 4,97
mm hari
Dr =
ef x 8, 64 NFR
=
4, 97 0,65 x 8, 64
=
0,89 ltrdtkHa h.
Februari 2 C
=
1 2
3
C C
C 3
+ +
= 0 0 0, 9 5
3 + +
= 0,32 Etc = ETo x C
= 5,06 x 0,32 = 1,60
mm hari
NFR = Etc + P - Re + WLR = 1,60 + 2,00 – 1,42 + 1,10
Universitas Sumatera Utara
= 3,28
mm hari
Dr =
ef x 8, 64 NFR
=
3, 28 0,65 x 8, 64
=
0,58 ltrdtkHa i.
Maret 2 M
= 1,1 x Eto + P = 1,1 x 4,99 + 2,00
= 7,49
mm hari
Dari tabel 2.8 didapat LP = Etc = 11,09 interpolasi NFR = LP – Re
= 11,09 – 2,14 = 8,95
mm hari
Dr =
ef x 8, 64 NFR
=
8, 95 0,65 x 8, 64
= 1,59 ltrdtkHa j.
April 1 M
= 1,1 x Eto + P = 1,1 x 4,41 + 2,00
= 6,85
mm hari
Dari tabel 2.8 didapat LP = Etc = 10,68 interpolasi NFR = LP – Re
Universitas Sumatera Utara
= 10,68 – 2,76 = 7,92
mm hari
Dr =
ef x 8, 64 NFR
=
7, 92 0,65 x 8, 64
= 1,41 ltrdtkHa k.
April 2 M
= 1,1 x Eto + P = 1,1 x 4,41 + 2,00
= 6,85
mm hari
Dari tabel 2.8 didapat LP = Etc = 10,68 interpolasi NFR = LP – Re
= 10,68 – 1,81 = 8,87
mm hari
Dr =
ef x 8, 64 NFR
=
8,87 0,65 x 8, 64
= 1,58 ltrdtkHa l.
Mei 1 C
=
1 2
3
C C
C 3
+ +
= 1, 05 1,10 1,10
3 +
+
Universitas Sumatera Utara
= 1,08 Etc = ETo x C
= 4,22 x 1,08 = 4,58
mm hari
NFR = Etc + P - Re + WLR = 4,58 + 2,00 – 4,60 + 1,10
= 3,08
mm hari
Dr =
ef x 8, 64 NFR
=
3, 08 0,65 x 8, 64
=
0,55 ltrdtkHa m.
Mei 2 C
=
1 2
3
C C
C 3
+ +
= 1, 05 1, 05 1,10
3 +
+
= 1,07 Etc = ETo x C
= 4,22 x 1,07 = 4,51
mm hari
NFR = Etc + P - Re + WLR = 4,51 + 2,00 – 2,60 + 1,10
= 5,01
mm hari
Universitas Sumatera Utara
Dr =
ef x 8, 64 NFR
=
5, 01 0,65 x 8, 64
=
0,89 ltrdtkHa n.
Juni 1 C
=
1 2
3
C C
C 3
+ +
= 0, 95 1, 05 1, 05
3 +
+
= 1,02 Etc = ETo x C
= 4,19 x 1,02 = 4,26
mm hari
NFR = Etc + P - Re + WLR = 4,26 + 2,00 – 3,69 + 1,10
= 4,78
mm hari
Dr =
ef x 8, 64 NFR
=
4, 78 0,65 x 8, 64
=
0,85 ltrdtkHa o.
Juni 2 C
=
1 2
3
C C
C 3
+ +
Universitas Sumatera Utara
= 0 0, 95 1, 05
3 +
+
= 0,67 Etc = ETo x C
= 4,19 x 0,67 = 2,80
mm hari
NFR = Etc + P - Re + WLR = 2,80 + 2,00 – 2,21 + 1,10
= 3,69
mm hari
Dr =
ef x 8, 64 NFR
=
3, 69 0,65 x 8, 64
=
0,66 ltrdtkHa p.
Juli 1 C
=
1 2
3
C C
C 3
+ +
= 0,50 0 0,95
3 + +
= 0,48 Etc = ETo x C
= 4,31 x 0,48 = 2.08
mm hari
NFR = Etc + P - Re + WLR = 2,08 + 2,00 – 2,40 + 1,10
Universitas Sumatera Utara
= 2,78
mm hari
Dr =
ef x 8, 64 NFR
=
2, 78 0,65 x 8, 64
=
0,50 ltrdtkHa q.
Juli 2 C
=
1 2
3
C C
C 3
+ +
= 0, 75 0,50 0
3 +
+
= 0,42 Etc = ETo x C
= 4,31 x 0,42 = 1,80
mm hari
NFR = Etc + P - Re + WLR = 1,80 + 2,00 – 3,76 + 0
= 0,04
mm hari
Dr =
ef x 8, 64 NFR
=
0, 04 0,65 x 8, 64
=
0,01 ltrdtkHa r.
Agustus 1 C
=
1 2
3
C C
C 3
+ +
Universitas Sumatera Utara
= 1, 00 0, 75 0, 50
3 +
+
= 0,75 Etc = ETo x C
= 4,79 x 0,75 = 3,59
mm hari
NFR = Etc + P - Re + WLR = 3,59 + 2,00 – 2,66 + 0
= 2,93
mm hari
Dr =
ef x 8, 64 NFR
=
2, 93 0,65 x 8, 64
=
0,52 ltrdtkHa s.
Agustus 2 C
=
1 2
3
C C
C 3
+ +
= 1, 00 1, 00 0, 75
3 +
+
= 0,92 Etc = ETo x C
= 4,79 x 0,92 = 4,39
mm hari
NFR = Etc + P - Re + WLR = 4,39 + 2,00 – 4,60 + 0
Universitas Sumatera Utara
=1,79
mm hari
Dr =
ef x 8, 64 NFR
=
1, 79 0,65 x 8, 64
=
0,32 ltrdtkHa t.
September 1 C
=
1 2
3
C C
C 3
+ +
= 0,82 1, 00 1, 00
3 +
+
= 0,94 Etc = ETo x C
= 4,88 x 0,94 = 4,59
mm hari
NFR = Etc + P - Re + WLR = 4,59 + 2,00 – 5,93 + 0
= 0,65
mm hari
Dr =
ef x 8, 64 NFR
=
0, 65 0,65 x 8, 64
=
0,12 ltrdtkHa u.
September 2 C
=
1 2
3
C C
C 3
+ +
Universitas Sumatera Utara
= 0, 45 0,82 1, 00
3 +
+
= 0,76 Etc = ETo x C
= 4,88 x 0,76 = 3,69
mm hari
NFR = Etc + P - Re + WLR = 3,69 + 2,00 – 7,53 + 0
= 0,00
mm hari
Dr =
ef x 8, 64 NFR
=
0,00 ltrdtkHa v.
Oktober 1 C
=
1 2
3
C C
C 3
+ +
= 0, 00 0, 45 0,82
3 +
+
= 0,42 Etc = ETo x C
= 4,61 x 0,42 = 1,95
mm hari
NFR = Etc + P - Re + WLR = 1,95 + 2,00 – 5,03 + 0
= 0,00
mm hari
Universitas Sumatera Utara
Dr =
ef x 8, 64 NFR
=
0,00 ltrdtkHa
w. Oktober 2
C =
1 2
3
C C
C 3
+ +
= 0, 00 0, 00 0, 45
3 +
+
= 0,15 Etc = ETo x C
= 4,61 x 0,15 = 0,69
mm hari
NFR = Etc + P - Re + WLR = 0,69 + 2,00 – 6,40 + 0
= 0,00
mm hari
Dr =
ef x 8, 64 NFR
=
0,00 ltrdtkHa
Hasil perhitungan dari alternative-1 sampai dengan alternative-12, dapat dilihat pada table 4.17 dibawah ini :
Tabel 4.17 Kebutuhan Air Irigasi
Universitas Sumatera Utara
No Bulan
Kebutuhan Air Irigasi DR Altr
- 1 Altr
- 2 Altr
- 3 Altr
- 4 Altr
- 5 Altr
- 6 Altr
- 7 Altr
- 8 Altr
- 9 Altr -
10 Altr -
11 Altr -
12 1
2 3
4 5
6 7
8 9
10 11
12 13
14 1
jan I
0.85 1.35
1.35 0.13
0.55 0.39
0.38 1.00
0.86 1.35
0.00 0.52
II 1.08
0.94 1.43
-0.01 0.48
0.61 0.20
0.60 0.92
1.43 1.43
0.32 2
Feb I
0.89 1.25
1.72 1.72
0.47 0.94
0.76 0.72
1.40 1.26
1.72 0.09
II 0.58
1.41 1.28
1.73 0.24
0.79 0.93
0.48 0.90
1.26 1.73
1.73 3
Mar I
0.00 0.96
1.32 1.79
1.79 0.55
1.01 0.84
0.80 1.47
1.33 1.79
II 1.55
0.41 1.23
1.09 1.55
0.06 0.60
0.75 0.30
0.72 1.07
1.55 4
Apr I
1.41 0.00
0.58 0.90
1.41 1.41
0.20 0.60
0.45 0.44
1.05 0.91
II 1.58
1.58 0.48
1.22 1.08
1.58 0.15
0.63 0.75
0.36 0.75
1.07 5
Mei I
0.55 1.05
0.00 0.24
0.54 1.05
1.05 0.00
0.24 0.10
0.10 0.69
II 0.79
1.31 1.31
0.22 0.94
0.80 1.31
-0.10 0.36
0.48 0.10
0.49 6
Juni I
0.85 0.70
1.21 0.00
0.39 0.69
1.21 1.21
0.02 0.40
0.26 0.26
II 0.57
0.87 1.39
1.39 0.31
1.03 0.88
1.39 -0.01
0.44 0.56
0.19 7
Juli I
0.47 1.08
0.93 1.43
0.00 0.61
0.92 1.43
1.43 0.23
0.62 0.48
II 0.00
0.39 0.69
1.21 1.21
0.12 0.85
0.71 1.21
0.00 0.26
0.38 8
Ags I
0.52 0.49
1.14 1.00
1.48 0.00
0.65 0.99
1.48 1.48
0.24 0.68
II 0.32
0.00 0.30
0.64 1.13
1.13 0.00
0.80 0.66
1.13 0.00
0.18 9
Sep I
0.12 0.00
0.00 0.57
0.44 0.91
0.00 0.07
0.42 0.91
0.91 0.00
II 0.00
0.00 0.00
0.00 0.14
0.62 0.62
0.00 0.29
0.15 0.62
0.00 10
Okt I
0.00 0.23
0.08 0.05
0.69 0.55
0.10 0.00
0.20 0.53
0.10 0.10
II 0.00
0.00 0.00
0.00 0.00
0.15 0.00
0.00 0.00
0.31 0.17
0.00 11
Nop I
1.15 0.00
0.34 0.19
0.18 0.79
0.64 1.15
0.00 0.32
0.63 1.15
II 0.83
0.00 0.00
0.00 0.00
0.01 0.31
0.83 0.83
0.00 0.47
0.33 12
Des I
1.21 1.21
0.00 0.40
0.26 0.25
0.85 0.71
1.21 0.00
0.39 0.70
II 0.83
1.33 -0.09
0.38 0.50
0.12 0.51
0.81 1.33
1.33 0.23
0.97
Sumber : Analisa perhitungan kebutuhan irigasi alternatif 1 sd 12
Universitas Sumatera Utara
4.5 Analisa Debit Andalan
