SISTEM IRRIGASI
Didik Suprayogo
Bahan Bacaan:
http://www.fao.org/docrep/R4082E/r4082e06.htm
IRRIGASI
Penyiapan tindakan yang memungkinkan petani
untuk menyediakan kecukupan air bagi
tanamannya yang dikumpulkan dan disalurkan
dari tempat lain
FUNGSI IRIGASI
Fungsi utama:
Memenuhi kebutuhan air tanaman
Fungsi spesifik:
1. mengambil air dari sumber (diverting)
2. Membawa/mengalirkan air dari sumber ke lahan
pertanian (conveying)
3. mendistribusikan air kepada tanaman (distributing)
4. mengatur dan mengukur aliran air (regulating and
measuring)
SISTEM IRRIGASI?
The irrigation system consists of:
• Diverting: a (main) intake
structure or (main) pumping
station,
• a conveyance system,
• a distribution system,
• regulating and measuring:
•
•
a field application system, and
a drainage system
SISTEM IRRIGASI
The (main) intake structure, or (main) pumping station, directs water from
the source of supply, such as a reservoir or a river, into the irrigation
system.
The conveyance system assures the transport of water from the main
intake structure or main pumping station up to the field ditches.
The distribution system assures the transport of water through field
ditches to the irrigated fields.
The field application system assures the transport of water within the
fields.
The drainage system removes the excess water (caused by rainfall and/or
irrigation) from the fields.
Pumping station
conveyance system
distribution system
field application system
MAIN INTAKE STRUCTURE
The intake structure is built at the entry to the irrigation system (see Fig. 70). Its
purpose is to direct water from the original source of supply (lake, river, reservoir
etc.) into the irrigation system.
PUMPING STATION
In some cases, the irrigation water source lies below the level of the irrigated
fields. Then a pump must be used to supply water to the irrigation system (see
Fig. 71).
PUMP
There are several types of pumps, but the most commonly used in irrigation is the
centrifugal pump.
The centrifugal pump (see Fig. 72a) consists of a case in which an element, called an
impeller, rotates driven by a motor (see Fig. 72b). Water enters the case at the center,
through the suction pipe. The water is immediately caught by the rapidly rotating
impeller and expelled through the discharge pipe.
BENDUNGAN URUGAN TANAH DAN
WADUK PERTANIAN (EMBUNG)
Sumber gambar : http://www.flickr.com/photos/erensdh/4025394008/
KEGUNAAN BENDUNGAN URUKAN TANAH DAN
WADUK PERTANIAN (EMBUNG)
Penyediaan air untuk irigasi
Mengendalikan atau mengontrol kelebihan air
Rancangan ditentukan integrasi anatara prinsip fisika tanah
dan mekanika tanah sebagai rancangan dan penerapan prinsip
prinsip konstruksi keteknikan
Tinggi konstruksi tidak lebih dari 15 m.
Bendungan dikonstruksi dari tumpukan tanah dimana bahan
tanah ditimbun merata secara berlapis dan dilanjutkan dengan
pemadatan pada kondisi kelembaban yang optimum untuk
mencapai kepadatan maksimum yang ditargetkan.
RANCANGAN BENDUNGAN URUKAN TANAH DAN
WADUK PERTANIAN (EMBUNG)
Rancangan untuk mengontrol air diprediksi atas
dasar:
Sifat pondasi, yaitu: stabilias, kedalaman pada lapisan yang kedap air,
permiabilitas tanah, dan kondisi drainase
Kondisi setempat dan ketersediaan bahan konstruksi
Macam Konstruksi:
Embung sederhana
Lapisan kedap air terpusat (core / Zoned type)
Tipe diafragma / pancang
Dasar waduk:
70% pasir, 20 s/d 25 % liat, dan cukup debu,
Tanah diurug 0.3 m di padatkan
Paling tidak 0,6 m harus ada tanah diatas batuan
Bila tidak ada bahan tsb, dapat dilakukan
campuran bentonit dg tanah dengan
minimum mengandung 10 s/d 15% pasir,
Atau dg polyphosfate, atau bahan kimia
lainnya, atau film plastic atau butyl
Blanket di perpanjang = 8 s/d 10 kali kedalaman waduk
Tebal Blanket = 10% kedalaman waduk, minimum 1m
Dari bahan plastik, butyl, beton, logam, kayu
PERSYARATAN PONDASI
Untuk bendung kecil cukup dengan bor tanah bila lebih besar perlu mengkaji
kondisi bawah tanah dan kondisi geologi, untuk uji mekanika tanah:
Distribusi ukuran partikel tanah
Indek plastis dan cair
Kekuatan geser tanah,
Kompressibilitas
Permiabilitas
Macam Pondasi:
Batuan pejal; kadang ada malahan bahaya bocor, untuk itu perlu sementasi / injeksi
bahan semen
Pasir halus yang seragam, bila dibawah “kepadatan kritis” (void ratio dimana tanah
mengalami deformasi walupun tanpa merubah volume), maka pondasi ini harus
dikonsolidasi untuk mencegah aliran akibat beban penggenangan
Pasir kasar dan kerikil, pada saat penggenangan akan mengaalami konsolidasi,
pelapisan bahan kedap air di bagian muka diperlukan untuk mencagah kebocoran,
Liat yang plastis, tekanan geser yang diakibatkan oleh berat bendungan harus lebih
kecil dari pada ketahanan geser bahan pondasi, side slope yang lebih mendatar
diperlukan untuk mengurangi tekanan geser
RANCANGAN YANG DISESUAIKAN BAHAN YANG TERSEDIA
Ranacangan ditetapkan pada keguanaan secara ekonomis
yang paling murah yang didasarkan dari bahan yang tersedia
di tempat bangunan
Rancangan Penampang melintang tergantung kondisi pondasi
dan ketersediaan bahan urukan, contoh: kombinasi lapisan
kedap air dan Lapisan kedap air terpusat dilakukan untuk
pondasi yang tidak kedap air yang dalam.
Untuk pemadatan dan kapasitas penahanan air:
Kerikil : pasir: debu: dan liat untuk kepadatan maksimum = < 20% kerikil, 2050% pasir, < 30% debu dan 15-25% liat
Tanah yang mudah mengembang dan mengkerut hanya di gunakan pada yang
tergenang,
Bahan organik tanah harus di kelupas dari konstruksi
AIR REMBESAN MELALUI BENDUNGAN
Air rembesan tergantung pada karakteristik bahan tanah baik
untuk pondasi dan urukannya.
Pemahaman dan pengetahuan posisi garis rembesan penting
untuk mengontrol rembesan.
Garis rembesan adalah garis diatas rembesan: diatas garis ini
tidak ada tekanan hidrostatis, dibawah garis ini ada tekanan
hidrostatis
Garis rembesan dipengaruhi: (1) permebilitas bahan urukan
dan pondasi, (2) posisi dan aliran air bawah tanah, (3) tipe dan
rancangan bendungan, (4) penggunaan perangkat drainase
untuk menampung rembesan dibagian bawah bangunan.
e =h/3
q = (K(h – e)/L)*((h + e)/ 2) = (K/2) * ((h2 – e2)/L) = (4Kh2/9L) q max
q = (4Kh2/9L)
e = 23/3 = 7.6 m
L = (2Z + h – e/2) cot α + W + 0.3M
L = (2X3 +23 – 7.6/2) x 1 +6+6.9 = 38.1 m
q = (4 x 0.0176 x 23 x 23)/ (9X 38.1)
q = 0.1086 m3/ d per lineal meter of length
PERLAKUAN PONDASI
Macam pondasi: (1) batu, (2) material bertekstur halus (liat
dan debu), material bertekstur kasar (pasir dan kerikil).
Bahan batu harus hati hati melihat sambungan, patahan
geologi, lapisan permiabel.
Bahan bertekstur halus: penglupasan bahan organik, buat
galian profil sedalam 0.6 s/d 1 m dengan lebar bawah 4 s/d 6
m
Bahan bertektus kasar: dibuat profil hingga kedalaman lapisan
kedap air, atau batuan, lebar bawah minimum 3 m s/d 6 m
Tinggi minimum lapisan kedap air sebagai penyumbat air adalah setengah
dari tinggi bendungan, side lope kurang dari 1:1,
Minimum lewbar bagian atas lapisan kedap air 1.2 m
Drainase:
SIDE SLOPE AND BERMS, TOP WIDTH
Kurang 15 m < tajam dari 3:1 bagian depan dan 2:1 bagian
belakang,
Bahan urukan kasar 3:1 atau 4:1
Top width bendungan < 5 m = 2.4 m,
Top width > 5 m W = 0.4 H + 1
Freeboard
h = 0.014 (Df) 1/2
Net and gross freeboard embung 0.6 ha, dimana panjang permukaan air = 183 m, asumsi
frost depth = 0.15 m, dengan periode ulang 25 th Q max = 4.00 m3/detik, dengan
kedalaman aliran spillway =0.3 m
H = 0.014 (183)1/2 = 0.19 m, flood storage depth = 0.6m
Net freeboard = 0.15 + 0.19 = 0.34 m
Gross freeboard = 0.34 + 0.3 + 0.6 = 1.24 m
Mechanical Spillways
CONVEYANCE AND DISTRIBUTION
SYSTEM
The conveyance and distribution
systems consist of canals
transporting the water through the
whole irrigation system. Canal
structures are required for the
control and measurement of the
water flow.
OPEN CANALS
An open canal, channel, or ditch, is
an open waterway whose purpose
is to carry water from one place to
another. Channels and canals refer
to main waterways supplying
water to one or more farms. Field
ditches have smaller dimensions
and convey water from the farm
entrance to the irrigated fields.
CANAL CHARACTERISTICS
According to the shape of their cross-section,
canals are called rectangular (a), triangular (b),
trapezoidal (c), circular (d), parabolic (e), and
irregular or natural (f) (see Fig. 73).
CANAL CHARACTERISTICS
The most commonly used canal cross-section in irrigation and
drainage, is the trapezoidal cross-section. For the purposes of
this publication, only this type of canal will be considered.
The typical cross-section of a trapezoidal canal is shown in
Figure 74.
CANAL CHARACTERISTICS
The freeboard of the canal is the height of the bank above the
highest water level anticipated. It is required to guard against
overtopping by waves or unexpected rises in the water level.
The side slope of the canal is expressed as ratio, namely the
vertical distance or height to the horizontal distance or width.
For example, if the side slope of the canal has a ratio of 1:2 (one
to two), this means that the horizontal distance (w) is two times
the vertical distance (h) (see Fig. 75).
A BOTTOM SLOPE OF A CANAL
EARTHEN CANALS
Earthen canals are simply dug in the ground and the bank is
made up from the removed earth, as illustrated in Figure 77a.
The disadvantages of earthen canals are the risk of the side
slopes collapsing and the water loss due to seepage. They also
require continuous maintenance (Fig. 77b) in order to control
weed growth and to repair damage done by livestock and
rodents.
LINED CANALS
Earthen canals can be lined with impermeable materials to
prevent excessive seepage and growth of weeds (Fig. 78).
Lining canals is also an effective way to control canal bottom
and bank erosion. The materials mostly used for canal lining are
concrete (in precast slabs or cast in place), brick or rock
masonry and asphaltic concrete (a mixture of sand, gravel and
asphalt).
The construction cost is much higher than for earthen canals.
Maintenance is reduced for lined canals, but skilled labour is
required.
CANAL EROSION
Canal bottom slope and water velocity are closely related, as the following example will show.
A cardboard sheet is lifted on one side 2 cm from the ground (see Fig. 79a). A small ball is
placed at the edge of the lifted side of the sheet. It starts rolling downward, following the
slope direction. The sheet edge is now lifted 5 cm from the ground (see Fig. 79b), creating a
steeper slope. The same ball placed on the top edge of the sheet rolls downward, but this time
much faster. The steeper the slope, the higher the velocity of the ball.
Water poured on the top edge of the sheet reacts exactly the same as the ball. It flows
downward and the steeper the slope, the higher the velocity of the flow.
Water flowing in steep canals
can reach very high velocities.
Soil particles along the bottom
and banks of an earthen canal
are then lifted, carried away by
the water flow, and deposited
downstream where they may
block the canal and silt up
structures. The canal is said to
be under erosion; the banks
might eventually collapse.
DROP STRUCTURES AND CHUTES
Drop structures or chutes are required to reduce the bottom
slope of canals lying on steeply sloping land in order to avoid
high velocity of the flow and risk of erosion. These structures
permit the canal to be constructed as a series of relatively flat
sections, each at a different elevation (see Fig. 80).
Drop structures take the water abruptly from a higher section
of the canal to a lower one. In a chute, the water does not drop
freely but is carried through a steep, lined canal section. Chutes
are used where there are big differences in the elevation of the
canal.
DISTRIBUTION CONTROL
STRUCTURES
Distribution control structures are
required for easy and accurate water
distribution within the irrigation system
and on the farm:
1. Division boxes
2. Turnouts
3. Checks
DIVISION BOXES
Division boxes are used to divide or direct the
flow of water between two or more canals or
ditches. Water enters the box through an
opening on one side and flows out through
openings on the other sides. These openings
are equipped with gates (see Fig. 81).
TURNOUTS
Turnouts are constructed in the bank of a canal.
They divert part of the water from the canal to
a smaller one.
Turnouts can be concrete structures (Fig. 82a),
or pipe structures (Fig. 82b).
CHECKS
To divert water from the field ditch to the
field, it is often necessary to raise the water
level in the ditch. Checks are structures
placed across the ditch to block it
temporarily and to raise the upstream water
level. Checks can be permanent structures
(Fig. 83a) or portable (Fig. 83b).
CROSSING STRUCTURES
It is often necessary to carry irrigation water
across roads, hillsides and natural depressions.
Crossing structures, such as flumes, culverts and
inverted siphons, are then required.
1. Flumes
2. Culverts
3. Inverted siphons
FLUMES
Flumes are used to carry irrigation water across
gullies, ravines or other natural depressions.
They are open canals made of wood (bamboo),
metal or concrete which often need to be
supported by pillars (Fig. 84).
CULVERTS
Culverts are used to carry the water across
roads. The structure consists of masonry or
concrete headwalls at the inlet and outlet
connected by a buried pipeline (Fig. 85).
INVERTED SIPHONS
When water has to be carried across a road
which is at the same level as or below the canal
bottom, an inverted siphon is used instead of a
culvert. The structure consists of an inlet and
outlet connected by a pipeline (Fig. 86). Inverted
siphons are also used to carry water across wide
depressions.
WATER MEASUREMENT STRUCTURES
The principal objective of measuring irrigation water is to
permit efficient distribution and application. By measuring
the flow of water, a farmer knows how much water is
applied during each irrigation.
In irrigation schemes where water costs are charged to the
farmer, water measurement provides a basis for estimating
water charges.
The most commonly used water measuring structures are
weirs and flumes. In these structures, the water depth is
read on a scale which is part of the structure. Using this
reading, the flow-rate is then computed from standard
formulas or obtained from standard tables prepared
specially for the structure.
WEIRS
In its simplest form, a weir consists of a wall of timber, metal or concrete
with an opening with fixed dimensions cut in its edge (see Fig. 87). The
opening, called a notch, may be rectangular, trapezoidal or triangular.
PARSHALL FLUMES
The Parshall flume consists of a metal or concrete channel
structure with three main sections: (1) a converging section at
the upstream end, leading to (2) a constricted or throat section
and (3) a diverging section at the downstream end (Fig. 88).
Depending on the flow condition (free flow or submerged flow),
the water depth readings are taken on one scale only (the
upstream one) or on both scales simultaneously.
CUT-THROAT FLUME
The cut-throat flume is similar to the Parshall flume, but
has no throat section, only converging and diverging
sections (see Fig. 89). Unlike the Parshall flume, the cutthroat flume has a flat bottom. Because it is easier to
construct and install, the cut-throat flume is often
preferred to the Parshall flume.
PENGUKURAN
DEBIT AIR
49
Pengertian Dasar
• Debit air adalah Jumlah air yang mengalir
pada suatu luasan persatuan waktu tertentu
misalnya:
(liter/detik) atau (liter/menit), (liter/detik)
atau (m3/menit)
50
Peralatan Pengukuran
Peralatan yang dapat digunakan untuk
mengukur debit air harus disesuaikan
dengan kondisi aliran air yang akan diukur
Debit aliran yang kecil (1 s/d 5 lt/dt) cukup
digunakan alat sederhana misalnya ember
untuk mengukur volume dan arloji, jam
tangan untuk mengukur waktu
51
Untuk debit yg sedang dan besar
( > 5 lt/det) maka diperlukan alat ukur yang
lebih baik dan lebih teliti
Peralatan tersebut antara lain dinamakan
current meter, yakni alat yang berfungsi
mengukur kecepatan aliran air dg sangat
teliti.
52
Dasar Perhitungan
• Rumus dasar:
• Q=AxV
Dimana :
Q = debit aliran (m3/det)
A
= Luas penampang aliran (m2)
V
= Kecepatan aliran air (m/det)
53
PENGUKURAN AIR DI PIPA
FAKULTAS PERTANIAN
UNIVERSITAS BRAWIJAYA
Debit Aliran Melalui Pipa
Debit aliran yang melalui pipa dapat diukur
debitnya dengan cara meletak suatu alat yang
disebut meter air.
Q =C A (2gh)1/2 C= 0.6
Prinsip kerja alat ini adalah merubah kecepatan
aliran air menjadi putaran baling-2 (propeller) dan
kemudian dirubah dalam satuan debit.
Alat elektrik, singnal listrik, solar panel, transmisi
radio
Meteran air
55
Mengukur debit air yang keluar dari Pipa
Untuk debit kecil dapat diukur dg peralatan
ember dan jam tangan
Q = A x V atau
Q = Vol / waktu
Ember
56
Contoh perhitungan
•
•
•
•
Volume ember 6 liter:
Waktu pengambilan air = 2 detik
Maka debit aliran adalah
Q = 6/2 = 3 liter/detik
Pengambilan air harus dilakukan minimal 5
kali agar didapatkan hasil yg cukup teliti,
dengan cara diambil harga rata-rata dari
semua nilai yg didapat
57
Memperkiraan debit yg
lewat Pipa tertutup
Q =AxV
A
= Luas penampang pipa (cm2 atau inc2)
V
= Kecepatan aliran lewat pipa (m/dt)
Contoh perhitungan :
Kondisi Pipa dianggap penuh air, maka
A = ¼ µ d2, , d = diameter pipa ( 4 inci=10 cm)
A = ¼ x3,14 x(10) 2 = 78,5 cm2
V = kecepatan air misal = 1 m/det=100 cm/dt, maka
Q = 78,5 x 100 = 7850 cm3/det= 7,85 lt/dt
1 hari = 24 jam=60 menit=86400 detik
Q = 7,85 x 86400 =678240 lt/dt=678,24 m3/hari
• Harga 1 m3=Rp 100,- = 67800,-/hari
• Harga 1 bln=30 hari = 30 x 67800 = Rp. 2.034.000,-/bln
58
PENGUKURAN AIR DI SALURAN
TERBUKA
FAKULTAS PERTANIAN
UNIVERSITAS BRAWIJAYA
Debit Air pada Saluran Irrigasi / Sungai
Untuk debit pada saluran irrigasi /sungai kecil
dapat diukur dengan cara sbb:
• Dengan menggunakan pelampung/gabus yang
diletakkan pada permukaan air yg sedang
mengalir dan dicatat waktunya menempuh jarak
tertentu
• Mengukur kedalaman air dan lebar saluran
/sungai dengan meteran
60
Contoh Gambar
2
1
10 m, t =…..det? Misal t = 10 det
V = 10 m/10 det = 1 m/det
b=2m
Bila rata aliran = 80% aliran pelampung
h = 0,5 m
A = b x h = 2 x 0,5 = 1 m2, maka
Q = A x V = 1 x 1 x 0.8 = 0.8 m3/det
61
Gambar Current Meter
62
63
PERSYARATAN PENGUKURAN DEBIT DI SUNGAI
Persyaratan yang di maksud antara, lain
meliputi :
1. Lokasi pengukuran;
2. Jumlah dan waktu pengukuran;
3. Peralatan, tenaga pelaksana dan dana.
64
1. Lokasi Pengukuran
Mempunyai pola aliran yang seragam,
kecepatan alirannya tidak terlalu lambat atau
terlalu cepat.
Pengukuran yang baik pada lokasi yang
mempunyai kecepatan aliran mulai dari 0,20
m/det sampai dengan 2,50 m/det;
kedalaman aliran pada penampang pengukuran
harus cukup, kedalaman aliran yang kurang dari
20 cm biasanya sulit diperoleh hasil Yang baik.
65
Jangan Pada aliran turbulen/bergolak Yang
disebabkan oleh batu-batu, vegetasi,
penyempitan lebar alur sungai
dilakukan pada alur sungai yang stabil atau lurus,
lokasi pengukuran debit mudah didatangi, tidak
tergantung dari keadaan cuaca khususnya pada
musim penghujan atau pada saat terjadi banjir;
66
2. Jumlah dan waktu pengukuran;
• Pelaksanaan pengukuran debit, hasilnya
harus dapat menggambarkan sebuah
lengkunng debit untuk sebuah penampang
basah yang tidak tetap,
• Jumlah pengukuran debit minimal 10 buah
untuk sebuah lengkung debit yang datanya
tersebar mulai keadaan aliran terendah
sampai tertinggi
67
• Sedangkan periode pelaksanaannya
tergantung daripada musim.
• Pada musim kemarau pada umumnya
cukup satu sampai dua kali selama
keadaan aliran masih tetap rendah.
• Pada musim penghujan memerlukan
frekuensi pengukuran Yang lebih banyak,
yaitu minimal 3 kali
68
Lengkung Debit
1,4
Tinggi air
(m)
1
0
2
Debit air
(m3/det)
5
69
3. Peralatan, tenaga pelaksana dan
dana
• Gabus, curret meter, arloji, meteran dll
• Mininal 1 -2 orang
• Tergantung situasi
70
Bangunan Pengukur Debit pada
Saluran Irigasi
1.Bangunan Cipoletti
Berbentuk Segi empat
2.Bangunan Thomson
H
B
Berbentuk setitiga
H
Q = a Hb
71
www.themegallery.com
• Pintu Sorong
H
B
Bila sungainya besar?
Bagaimana cara mengukurnya?
• Misal lebar sungai = 20 meter
• Kedalaman air 2 meter
• Berapa debit nya?
b=
m?
h =…m?
74
FIELD APPLICATION SYSTEMS
There are many methods of applying water to
the field. The simplest one consists of
bringing water from the source of supply,
such as a well, to each plant with a bucket or
a water-can (see Fig. 90).
This is a very time-consuming method and it
involves quite heavy work. However, it can be
used successfully to irrigate small plots of
land, such as vegetable gardens, that are in
the neighbourhood of a water source.
More sophisticated methods of water
application are used in larger irrigation
systems. There are three basic methods:
Surface irrigation
Sprinkler irrigation
Drip irrigation
SURFACE IRRIGATION
Surface irrigation is the application of
water to the fields at ground level.
Either the entire field is flooded or the
water is directed into furrows or
borders.
Furrow irrigation
Border irrigation
Basin irrigation
FURROW IRRIGATION
Furrows are narrow ditches dug on the field between the
rows of crops. The water runs along them as it moves down
the slope of the field.
The water flows from the field ditch into the furrows by
opening up the bank or dyke of the ditch (see Fig. 91a) or by
means of syphons or spiles. Siphons are small curved pipes
that deliver water over the ditch bank (see Fig. 91b). Spiles
are small pipes buried in the ditch bank (see Fig. 91c).
BORDER IRRIGATION
In border irrigation, the field to be irrigated is divided into strips (also called
borders or borderstrips) by parallel dykes or border ridges (see Fig. 92).
The water is released from the field ditch onto the border through gate
structures called outlets (see Fig. 92). The water can also be released by means
of siphons or spiles. The sheet of flowing water moves down the slope of the
border, guided by the border ridges.
Perkiraan aliran (l/detik) pada siphons
H
H (cm)
Diameter siphons (mm)
27
34
42
53
63
76
5
0.3
0.6
0.9
1.5
2.1
3.1
7
0.4
0.7
1.1
1.8
2.5
3.7
10
0.5
0.8
1.3
2.1
3.0
4.5
15
0.6
1.0
1.6
2.6
3.7
5.5
20
0.7
1.1
1.8
3.0
4.3
6.3
30
0.8
1.4
2.2
3.6
5.2
7.7
50
1.1
1.8
2.8
4.7
6.8
10.0
PANJANG MAKSIMUM IRRIGASI ALUR
(m)
Q
max
(l/s)
S
(%)
Rata-rata kedalaman air yang diterapkan (m)
75
150
225
30
0
50
Liat
100
150
200
50
75
Lempung
100
125
Pasir
6.0
0.1
340
440
470
50
0
180
340
440
470
90
120
190
220
1.2
0.5
400
500
560
75
0
280
370
470
530
120
190
250
300
0.3
2.0
220
270
340
40
0
180
250
250
340
60
90
150
190
BASIN IRRIGATION
Basins are horizontal, flat plots of land, surrounded by small dykes or
bunds. The banks prevent the water from flowing to the surrounding
fields. Basin irrigation is commonly used for rice grown on flat lands or
in terraces on hillsides (see Fig. 93a). Trees can also be grown in basins,
where one tree usually is located in the centre of a small basin (see Fig.
93b).
SPRINKLER IRRIGATION
With sprinkler irrigation, artificial rainfall is created. The water is led to the field
through a pipe system in which the water is under pressure. The spraying is
accomplished by using several rotating sprinkler heads or spray nozzles (see
Fig. 94a) or a single gun type sprinkler (see Fig. 94b).
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Irigasi dalam budidaya tanaman tebu di GMP : tujuan
•
Menekan kejadian defisit air yang
dialami oleh tanaman tebu : durasi,
intensitas, dan luasan tanaman yang
menderita
•
Menekan kehilangan hasil pasca
musim kemarau yang ekstrim hingga
sekecil mungkin
•
Memantapkan tingkat produksi dari
tahun ke tahun dan mening-katkan
produktivitas secara sinambung
Irigasi dalam budidaya tebu di GMP :
pendekatan
•
Pengembangan potensi sumber-daya
air : pengukuran dan peme-taan;
identifikasi karakter sumber air;
reklamasi sumber/badan air
•
Pemeliharaan dan pelestarian
sumberdaya air : penghijauan DAS;
pengendalian erosi; pengendalian
gulma air dan gulma terestrial
•
Penguasaan teknik aplikasi irigasi :
pengetahuan dasar, perhitungan,
pemilihan sistem, penyediaan
prasarana dan sarana
•
Penyesuaian budidaya : bulan tanam,
block system
Irigasi dalam budidaya tebu di GMP : pilihan
sistem aplikasi
•
Perhitungan kebutuhan air tanaman
•
Penentuan prioritas stadia pertumbuhan tanaman yang diirigasi
•
Irigasi curah vs irigasi tetes vs irigasi
alur
•
Irigasi curah : big-gun mobile
sprinkler vs travelling irrigator
DRIP IRRIGATION
In drip irrigation, also called trickle irrigation, the water is led to the field
through a pipe system. On the field, next to the row of plants or trees, a tube is
installed. At regular intervals, near the plants or trees, a hole is made in the
tube and equipped with an emitter. The water is supplied slowly, drop by drop,
to the plants through these emitters (Fig. 95).
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DRAINAGE SYSTEM
(A drainage system is necessary to remove excess water from the irrigated land. This
excess water may be e.g. waste water from irrigation or surface runoff from rainfall. It
may also include leakage or seepage water from the distribution system.
Excess surface water is removed through shallow open drains (see Surface drainage,
Chapter 6.2.1). Excess groundwater is removed through deep open drains or
underground pipes (see Subsurface drainage, Chapter 6.2.2).
TUGAS KUALITAS AIR IRIGASI
1. Pemerintah telah mengeluarkan standar kualitas Air
Irigasi, untuk itu dari standar tersebut, melalui studi
literatur deskripsikan teknik mengukur masing-masing
standar kualitas air irrigasi tersebut. Mengapa kualitas
tersebut penting bagi pertanian.
2. Kualitas Air di sepanjang Sungai Brantas telah di lakukan
monitoring secara periodik oleh Perum Jasa Tirta,
tetapkan wilayah pengairan yang memenuhi standar air
irrigasi dan wilayah pengairan yang tidak memenuhi
standar air irrigasi, dari waktu kewaktu.
3. Melalui kajian literatur, beri rekomendasi bagaimana cara
agar wilayah pengairan yang tidak memenuhi standar
kualitas air irigasi menjadi air irigasi yang memenuhi
standar kualitas air irigasi bagi usaha pertanian.
STRATEGI KONSERVASI AIR
(1) REDUCE PLANT WATER DEMAND
A. Plant selection
B. Site landscape design
C. Plant cultural practices
D. Root zone depth
E. Mulching
F. Soil amendments
(2) MAXIMISE IRRIGATION APPLICATION EFFICIENCY
(3) PRECISE CONTROL OF IRRIGATION
(4) ADOPT NEW TECHNOLOGIES
(5) OPERATOR SKILLS
STRATEGI KONSERVASI AIR
(1) REDUCE PLANT WATER DEMAND
(2) MAXIMISE IRRIGATION APPLICATION EFFICIENCY
A. High uniformity
B. Optimise hydraulic operating conditions for outlets
C. Correct outlet selection
D. Effective outlet coverage
E. Effective functioning of equipment
F. Low head drainage
(3) PRECISE CONTROL OF IRRIGATION
(4) ADOPT NEW TECHNOLOGIES
(5) OPERATOR SKILLS
STRATEGI KONSERVASI AIR
(1) REDUCE PLANT WATER DEMAND
(2) MAXIMISE IRRIGATION APPLICATION EFFICIENCY
(3) PRECISE CONTROL OF IRRIGATION
A. Match irrigation to plant water demand
B. Correct depth of irrigation
C. Hydrozones
(4) ADOPT NEW TECHNOLOGIES
A. Weather stations
B. Soil moisture sensors
C. Smart controllers
D. Alternative method of irrigation - Subsurface drip
(5) OPERATOR SKILLS
TERIMAKASIH