AUDIT SISTEM IRRIGASI

Didik Suprayogo

Bahan Bacaan: Connellan, 2002. Efficient Irrigation: A Reference Manual for Turf and Landscape, Burnley College, University of Melbourne,

Sumber Gambar: Irrigation Australia

APA ITU AUDIT SISTEM IRRIGASI?

determination of current efficiency

- BEFORE making major changes - BEFORE making major changes

(uniformity, leaks, …)

ASPEK PERTIMBANGAN KEPUTUSAN MENGIRIGASI

LAHAN PERTANIAN

� Lingkungan,

� Sistem Budidaya Pertanian,

� Nilai Ekonomi,

� Kemampuan personnel dalam menjalankan irigasi� Kemampuan personnel dalam menjalankan irigasi

� Kebutuhan masyarakat dan

� Dampak Lingkungan

RENCANA MANAGEMEN AIR DI LAHAN

� Akurasi rancangan lahan irrigasi termasuk sistem irigasinya

� Karakteristik, jumlah, laju aliran dan kualitas pasokan air

� Penilian sistem Pertanian yang diterapkan– Perkiraan kebutuhan air

� Faktor Pembatas Ketersediaan Air – dan implikasinya pada lahan

� Strategi untuk mengatasi kekeringan

� Jenis dan sifat Tanah serta kedalaman zona akar

� Jadwal Irigasi� Jadwal Irigasi

� target kinerja Sistem

� Isu Kualitas air

� Biaya air

� Dampak terhadap lingkungan sebagai akibat praktek irigasi

� Ketrampilan dan pelatihan staf

� Strategi untuk mengadopsi teknologi baru

� Evaluasi sistem manajemen dan efisiensi irrigasi secara berkala

� Prosedur perawatan

� Dokumentasi perbaikan sistem irigasi

ISUE UTAMA IRRIGASI: EFISIENSI

� Kualitas rancangan sistem irigasi

yang tinggi

� Pemasangan sistem sesuai

dengan kualitas rancangandengan kualitas rancangan

� Standar tinggi pemeliharaan

hardware di sistem / peralatan

� Presisi manajemen dan kontrol

(penjadwalan) dari sistem irigasi

PENYEBAB UTAMA KEBOROSAN AIR: TIDAK EFFISIEN

� Jumlah air diterapkan melebihi dari kebutuhantanaman

� Kurang seragamnya aplikasi air

� Tingkat curah hujan lebih tinggi dari tingkat infiltrasitanahtanah

� Rusak atau tidak berfungsi peralatan

� Bila menggunakan irrigasi springkler: Beroperasidalam kondisi berangin

� Limpasan permukaan

� Penyemprotan yang berlebihan dari dari alatsprinkler dan karena salah arah penyiramannya

PRINSIP PRAKTEK IRRIGASI YANG BAIK

� (A) Jumlah air yang diterapkan adalah sesuai kebutuhan tanaman dan kondisi tanah

� (B) Waktu aplikasi air sesuai dengan kebutuhan tanaman dan kondisi cuaca

� (C) Air diterapkan secara seragam dan efektif

� (D) Air diterapkan pada zona akar tanaman tanpa kehilangan akibat limpasan

permukaan, drainase dalam, kurang efektifnya cakupan irrigasi dan penyebab lainnya.

PRINSIP PRAKTEK IRRIGASI YANG BAIK

Irrigasi yang baik adalah aplikasi air irrigasi yang

efisien dengan jumlah air yang tepat dengan efisien dengan jumlah air yang tepat dengan

pemberian air pada tanaman pada waktu yang tepat

dan di tempat yang tepat.

(A) PENERAPAN KEDALAMAN IRRIGASI YANG TEPAT

� AirTersedia bagi Tanaman (ATT) = Kedalaman Zona

Perakaran (D) x Air yang Tersedia bagi tanaman

(AT) mm/m.

� contoh:� contoh:

� Tanaman Jagung yang tumbuh di tanah lempung

berpasir

� Kedalaman zona Perakaran (D): 150 mm

� Kapasitas penyimpanan air tersedia (AT): 110 mm /

1000 mm

� ATT = 150 mm x (110/1000) = 16,5 mm

(A) PENERAPAN KEDALAMAN IRRIGASI YANG TEPAT

� AirTersedia bagi Tanaman = Kedalaman Zona

Perakaran (D) x Air yang Tersedia bagi tanaman

(AT) mm/m.

� contoh:� contoh:� Tanaman Jagung yang tumbuh di tanah lempung berpasir

� Kedalaman zona Perakaran (D): 150 mm

� Kapasitas penyimpanan air tersedia (AT): 110 mm / 1000 mm

� ATT = 150 mm x (110/1000) = 16,5 mm

� Point Refill (Target Isi Ulang)

� Aplikasi Sistem Efisiensi

(A) PENERAPAN KEDALAMAN IRRIGASI YANG TEPAT

� Kedalaman irrigasi = (% pengurangan kandungan

air tanah yg diperbolehkan X ATT)/ Efisiensi

Aplikasi (%)

� contoh:� contoh:� Lahan pertanian : Jagung di tanah lempung berpasir

� Irrigasi : sprinklers

� ATT : 16.5 mm

� Depletasi yng diperbolehkan (%) : 50%

� Kedalaman depletasi yg diperbolehkan : 8.3 mm

� Efisiensi aplikasi: 75%

� Kedalaman irrigasi : 11.0 mm ( = 0.5 x 16.5)/ 0.75

(B) WAKTU IRRIGASI YANG TEPAT

� Faktor: � (1) karakteristik tanaman dalam penggunaan air

� (2) kondisi Iklim

� (3) tingkat kelembaban tanah dan penyimpanan air tanah

� Menentukan Evapotranspirasi mm/hari dengan� Menentukan Evapotranspirasi mm/hari denganfaktor:

1. Jenis tumbuhan

2. Tahap pertumbuhan

3. Cuaca - permintaan menguapkan

4. Tersedia air di tanah

5. Kualitas air

(B) FAKTOR IKLIM YANG MEMPENGARUHI

EVAPOTRANSPIRASI

� 1.Radiasi matahari - menyediakan energi untuk

penguapan

� 2.Suhu udara

� 3.Kelembaban relatif - menunjukkan kekeringan � 3.Kelembaban relatif - menunjukkan kekeringan

udara

� 4.Kecepatan angin - air meningkat tingkat

penggunaan

Kandungan air

Hujan

LP

Infiltrasi

Evapotranspirasi

Irigasi

Kandungan air

pada sistem

perakaran pada

kondisi kapasitas

lapangan

Drainase

(B) TEKNIK UNTUK MENGESTIMASI PENGGUNAAN AIR

Evapotransiparsi maksimum (Etm)

CropWat

EVAPOTRANSPIRASI MAKSIMUM (ETm)

• Crop water use, Consumptive use , and Evapo-transpiration (ETm) are the terms

that are interchangeably used to describe water consumed by crops.

• Water requirements depend mainly on the nature and stage of growth of crop and

environmental conditions.

• Crops will transpire water at the maximum rate when soil water is at field capacity.

Transpiration rate does not decrease significantly until the soil moisture falls below

50% of field capacity.

The DATA STATUS Window

EVAPOTRANSPIRASI MAKSIMUM (ETm)

ETm = kc * ETo ETo = Reference Evapotranspirasi

kc = Koefisien Tanaman

ETo = c [W*Rn + (1-W)*f(U)*(ea-ed) Penman Methods

(ea-ed) = selisih kelembaban udara (kelembaban jenuh – kelembaban aktual)

= ed = ea*RH/100

f(U) = fungsi kecepatan angin f(U) = 0.27 (1+U/100)

Rn = total radiasi bersih =0.75Rs-Rn1; Rs radiasi gelombang pendek, Rnl = radiasi

gelombang panjang, sebagai fungsi temperatur; f(T) =kelembaban, lama

penyinaran,

W = faktor pemberat tempartur dan tinggi tempat

c = faktor penentu dari rasio Uday/Unight, untuk RHmax dan untuk Rs.

ETo = c (W*Rs) (Radiation Method) ETo = kpan * Epan

(Pan Evaporation Method)

Reference Crop Evapotranspiration (ETo) values

kc

Crop coefficient is dynamic in nature and varies with crop characteristics, dates of

planting, stage of growth , height, soil and canopy cover, albedos etc.

For practical reasons, four stages of crop growthare assumed:

1.Initial Stage (10% g. cover) 2. Crop Development Stage (10-80%, 3. Mid-season Stage 1.Initial Stage (10% g. cover) 2. Crop Development Stage (10-80%, 3. Mid-season Stage

(.80%-rippening) 4. Late-season Stage (rippening – harvest)

Tanaman CROP WATER STAGES

Initial C develop Mid season Late season Harvest Rata-rata

Padi 1.1 1.1 1.1 0.95 0.95 1.05

Jagungsweet 0.3 0.7 1.05 1.0 0.95 0.8

Kedelai 0.3 0.7 1.0 0.70 0.40 0.75

KacangTanah 0.4 0.7 0.95 0.75 0.55 0.75

KacangHijau 0.3 0.65 0.95 0.9 0.85 0.85

UbiJalar

UbikayuUbikayu

Talasbentul

Semangka 0.4 0.7 0.95 0.8 0.65 0.75

Kangkungd

Tomat 0.4 0.7 1.05 0.8 0.6 0.75

Cabe 0.3 0.6 0.95 0.85 0.8 0.7

Kubisbunga 0.4 0.7 0.95 0.9 0.8 0.7

BawangMer 0.4 0.7 0.95 0.85 0.75 0.8

KacangPanj 0.3 0.7 1.05 0.65 0.25 0.7

Tanaman CROP WATER STAGES

Initial C develop Mid season Late season Harvest Rata-rata

Kubis 0.4 0.7 0.95 0.9 0.8 0.7

Tembakau 0.3 0.7 1.0 0.9 0.75 0.85

Tebu 0.4 0.7 1.0 0.75 0.5 0.85

Kenaf

JarakPagar

Kopi

Kaka0

Data needed for calculations

• For Crop Water Requirements (CWR):

1. Reference Crop Evapotranspiration (ETo) values

2. A Cropping Pattern

3. Monthly Rainfall data3. Monthly Rainfall data

• For Irrigation Scheduling you will need the data listed above and -

4. Soil Type information

5. Scheduling Criteria

EVAPOTRANSPIRASI AKTUAL (ETa)

1. Cukup air tanah untuk memenuhi ETa = ETm

2. Keterbatasan air tanah, ETa < ETm

2.1. ETa melalui interval irrigasi

2.2. ETa melalui Periode bulanan

Untuk menetapkan penjadwalan irrigasi

Irrigation schedulling

I.Supply right quantity of water at right time through an appropriate application method to

satisfy crop water requirements.

II.Serves the objective of high yield of good quality, attaining high WUE, without any damage

to soil productivity and applying water at reasonable cost.Irrigation Scheduling

Criterion of irrigation schedulingCriterion of irrigation scheduling

Crop Growth Stages-Physiological/ Critical

•Soil Moisture Depletion

•Meteorological Indicators

•Plant Indices

General Criterion for Scheduling

1. When farmers have adequate supplies of water as per

demand, the aim is to achieve maximum yield per

unit of land without wasting water.

2. In case of limited amount of water, the aim is to 2. In case of limited amount of water, the aim is to

maximize production per unit of water by

rationalizing its distribution over available land and

also applying it at more sensitive stages of crop

growth.

(C) KETIDAK KESERAGAMAN APLIKASI AIR IRRIGASI:

KASUS DI IRRIGASI SPRINKLER

� Sprinklers and sprays spaced too far apart

� Poor sprinkler precipitation distribution profile

� Unfavourable environmental operating conditions - wind- wind

� Incorrect operating pressure

� Incorrect nozzle size

� Poor pipe and valve sizing - excessive pressure and flow variation in system

� Sprinkler head or equipment not functioning effectively.

(C) MENGHINDARI KELEBIHAN AIR

� Runoff - design or management problem

� Wind - droplet evaporation losses and distorted

wetting pattern

� Misdirected sprays and sprinklers� Misdirected sprays and sprinklers

� Incorrect operating pressure

� Obstructed distribution for sprinkler and sprays

� Blocked nozzles

MENGEVALUASI KINERJA IRIGASI:

(1) THE AVERAGE PRECIPITATION RATE AND

(2) THE EVENNESS OR UNIFORMITY OF THE APPLICATION.

KECEPATAN ALIRAN “HUJAN”

� Calculating Theoretical Precipitation Rate:

Theoretical/ Calculated PR (mm/h) = (Outlet flow rate)/ (Wetted Area)

Precipitation rate PR = (q x 60)/ (S x L) mm/h

q - flow rate from one outlet (sprinkler or spray) (L/min)

S - spacing between outlets along lateral (m)

L - perpendicular spacing between laterals (m)

� Calculating Actual Precipitation Rate:

Actual Precipitation Rate (PR) = (Vavg x 60,000)/ (T x Ac) mm/h

Vavg - average volume in test cans (mL)

T - test run time in minutes

Ac - area of can in mm2

UNIFORMITY COEFFICIENTS

� Distribution Uniformity (DU) Coefficient:

DU (%) = (M25 x 100)/ M

where:

M - average value of all catch can readings.

M25 - average of lowest 25% of readings , minimum DU of 75%.

•Christiansen Coefficient of Uniformity (Cu):

Cu = ( 1 - Σ Md ) (M x n) x 100 %

M - average value of all can readings

Σ Md - total of variation of each reading from the average

n - number of can readings

Cu be greater than 84%

UNIFORMITY COEFFICIENTS

� Scheduling Coefficient (SC):

Scheduling Coefficient (SC) = (Average of all can readings)/(Selected

can/s readings (Dry area))

SC25% = (1/DU)SC25% = (1/DU)

Eg. If DU is 75%, then SC25% = = (1/0.75) = 1.33

IRRIGATION MANAGEMENT INDICATOR

Irrigation Index (Ii) =

(Water Applied to site (WA))/(Estimated Water

Required (WR))

Determining Water Applied (WA):

Water applied (WA) = Water applied (WA) =

(Volume of water supplied to site (Litres))/ (Irrigated

area (m2)) mm

Seasonal Water Required (WR)

Net Water Requirement (NWR) = (ETc – Peff) (mm)

Estimated Irrigation Water Required (WA) =

(Net Water Requirement (NWR))/ (System Application Efficiency

(Ns)) mm

LIST OF KEY PERFORMANCE INDICATORS

• System precipitation rate - PR (mm per hour): A measure of the

average rate of water reaching the soil surface within the test area.

This should be less than soil infiltration rate to avoid runoff.

• Distribution Uniformity - DU (Should be greater than 75%): A

measure of the evenness of application of water application by measure of the evenness of application of water application by

sprinkler systems using a can test. This coefficient takes into account

the average of the lowest 25% of readings obtained from test cans

and compares this value to the average of all readings.

• Christiansen Uniformity - Cu (Should be greater than 84%): A

measure of the evenness of application of water application by

sprinkler systems. This coefficient takes into account the amount of

variation in test can readings both above and below the average

value of all can readings. It is in more common use in agriculture.

LIST OF KEY PERFORMANCE INDICATORS

• Scheduling Coefficient - SC (SC25% should be less

than 1.3): A measure of the range of depths of

water applied by the irrigation system within the

test area. Provides a basis for adjusting irrigation

run times to allow for underwatered areas.

• Irrigation Index - Ii ( Should not be greater than

1.0): Ratio of the depth of water applied at a site

compared to the depth of water that has been

estimated to be required.

AUDIT SISTEM IRRIGASI:

STUDI KASUS SPRINKLER IRRIGATION

KEUNTUNGAN POTENSIAL AUDIT

� Potential water savings and cost savings

� Nutrient savings and reduced release of nutrients

to environments

� Higher quality of land and landscape plantings eg. � Higher quality of land and landscape plantings eg.

more uniform land surfaces

� Savings in time and labour

� Improved management of a valuable resource

KETERSEDIAAN INFORMASI HASIL AUDIT

� Identify faulty equipment

� Current operating efficiency and uniformity of the

system

� Identify any weaknesses in system� Identify any weaknesses in system

� Establish key system performance parameters

pressure, flow rate, precipitation rate

� Provide basis for developing an irrigation schedule

for the site How much to apply, when to apply.

PERSIAPAN AUDIT

� Background Information: (a) an accurate record of the system, the

site and the vegetation; (b) quality irrigation management program (accurate details of equipment); (c) Details of the water supply and control equipment (pump or water meter, controller, master valves, etc); (d) The soil water properties for each irrigated zone need to be determined. The key properties are infiltration rate and available water holding capacity

Site Test Conditions - Weather and Hydraulics� Site Test Conditions - Weather and Hydraulics

� Preliminary Check Of System: (a) Malfunctioning

valves, (b) Sunken sprinkler heads, (c) Incorrect or non-rotation of sprinkler heads, (d) Tilted heads, (e) Plugged nozzles, (f) Broken casings and missing parts, (g) Distorted spray distribution, (h) Incorrect nozzles installed, (i) Leaking pipes, valves, fittings, equipment, broken seals, (j) ncorrectoperating pressure - high, low

PELAKSANAAN AUDIT

� Audit Test Equipment ; (a) Setting Out The Cans,

(b) Pressure Testing: (1) Checking the outlets

(sprinklers and sprays) are operating at correct

(optimum) pressure. (2) The pressure variation (optimum) pressure. (2) The pressure variation

along the lateral Is it acceptable? (3) The pressure

variation between stations and outlets in

different parts of the system. (4) The amount of

pressure loss due to friction in the system. (5) The

pressure loss across valves, filters and special

fittings.

frequent irrigation audits in

a variety of situations. Also

has the necessary tools for

more in-depth sprinkler

hydraulic analysis. Kit

includes:

Mobile Equipment Cart

Oakfield Model 'B' Soil

Probe

30 - Catch Can (Premium)

30 - Catch Can Stand

(Stainless Steel)(Stainless Steel)

100' Fiberglass Tape

Measure

50 Marking Flags

POC Pressure Gauge

Rotor Head Pressure Gauge

Spray Head Pressure Gauge

Stop Watch

Anemometer

Premium Audit Kits Premium

Audit Kit B

"you already have a soil probe"

Click to Enlarge

This kit includes all the tools in the

Premium Audit Kit A, without the

soil probe. This kit is for

performing frequent irrigation

audits in a variety of situations.

Also has the necessary tools for

more in-depth sprinkler hydraulic

analysis. Kit includes:

Mobile Equipment CartMobile Equipment Cart

30 - Catch Can (Premium)

30 - Catch Can Stand (Stainless

Steel)

100' Fiberglass Tape Measure

50 - Marking Flags

POC Pressure Gauge

Rotor Head Pressure Gauge

Spray Head Pressure Gauge

Stop Watch

Anemometer

MENGANALISA HASIL AUDIT

� (1) the evenness or uniformity of the application and (2) the average precipitation rate.

� Precipitation Rate Results: actual precipitation rate should be less than the soil infiltration rate;

� Uniformity Results: DU greater than 75% and Cu � Uniformity Results: DU greater than 75% and Cu greater than 84%.

� Developing An Irrigation Schedule:� Run Time = (Irrigation Depth (mm) x 60 min/ (Precipitation Rate (PR) (mm/h)

Example - Irrigation Run Time

Site: sports oval

Turf: kikuyu

Irrigation Depth: 8.3 mm

Precipitation Rate: 12 mm/h (This is an assumed value)

Run Time = (8.3 x 60)/ 12 = 41.5 min

STRATEGI KONSERVASI AIR

� (1) REDUCE PLANT WATER DEMAND

� A. Plant selection

� B. Site landscape design

� C. Plant cultural practices

� D. Root zone depth� 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� 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� 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

TUGAS MEMAHAMI & MENGINTERPRETASI

THE RAPID APPRAISAL PROCEDURE BY FAO (1999)

INTERNAL INDICATORS

The internal indicators assess quantitatively the internal

processes (the inputs [resources used] and the outputs

[services to downstream users]) of an irrigation project.

Internal indicators are related to operational procedures, the

management and institutional setup, hardware of the system,

water delivery service, etc. These indicators are necessary in water delivery service, etc. These indicators are necessary in

order to have a comprehensive understanding of the

processes that influence water delivery service and the

overall performance of a system. Thus, they provide insight

into what could or should be done in order to improve water

delivery service and overall performance (the external

indicators).

EXTERNAL INDICATORS

The external indicators compare the inputs and outputs of an

irrigation system in order to describe overall performance.

These indicators are expressions of various forms of

efficiency, e.g. water-use efficiency, crop yield, and budget.

They do not provide any detail on what internal processes

lead to these outputs and what should be done in order to lead to these outputs and what should be done in order to

improve performance. However, they could be used for

comparing the performance of different irrigation projects

both nationally and internationally. Once these external

indicators have been computed, they can be used as a

benchmark for monitoring the impacts of modernization on

improvements in overall performance.

LANGKAH MENGERJAKAN TUGAS

1. Lakukan diskusi kelompok, untuk memahami Proses

Penilaian Cepat (RAP) dan Acuan (Benchmarking)

Penjelasan dan Pirantinya sistem Irigasi dan Cara mengisi

Form Isian dalam exel file. Buat daftar bagian mana yang

belum dapat dipahami dan belum bisa mengisi form

tersebut, dan kumpulkan satu minggu setelah kuliah ini.tersebut, dan kumpulkan satu minggu setelah kuliah ini.

2. Lakakuan interpretasi hasil RAP contoh (file exel), secara

mandiri terkait kinerja sistem irrigasi tersebut. Tugas ini

dibuat secara mandiri dan dikumpulkan 2 (dua) minggu

setelah kuliah ini.

Terimakasih