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 (uniformity, leaks, …)
ASPEK PERTIMBANGAN KEPUTUSAN MENGIRIGASI LAHAN PERTANIAN
Lingkungan, Sistem Budidaya Pertanian, Nilai Ekonomi, 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 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 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 kebutuhan tanaman Kurang seragamnya aplikasi air Tingkat curah hujan lebih tinggi dari tingkat infiltrasi tanah Rusak atau tidak berfungsi peralatan Bila menggunakan irrigasi springkler: Beroperasi dalam kondisi berangin Limpasan permukaan Penyemprotan yang berlebihan dari dari alat sprinkler 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 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: 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:
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:
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) (2) (3)
karakteristik tanaman dalam penggunaan air kondisi Iklim tingkat kelembaban tanah dan penyimpanan air tanah
Menentukan Evapotranspirasi mm/hari dengan faktor: 1. 2. 3. 4. 5.
Jenis tumbuhan Tahap pertumbuhan Cuaca - permintaan menguapkan Tersedia air di tanah Kualitas air
(B) FAKTOR IKLIM YANG MEMPENGARUHI EVAPOTRANSPIRASI 1.Radiasi matahari - menyediakan energi untuk penguapan 2.Suhu udara 3.Kelembaban relatif - menunjukkan kekeringan udara 4.Kecepatan angin - air meningkat tingkat penggunaan
Hujan Evapotranspirasi
Irigasi
LP Infiltrasi
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 (.80%-rippening) 4. Late-season Stage (rippening – harvest)
Tanaman
CROP Initial
C develop
WATER STAGES
Mid season
Late season
Harvest
Rata-rata
Padi
1.1
1.1
1.1
0.95
0.95
1.05
Jagung sweet
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
Kacang Tanah
0.4
0.7
0.95
0.75
0.55
0.75
Kacang Hijau
0.3
0.65
0.95
0.9
0.85
0.85
0.4
0.7
0.95
0.8
0.65
0.75
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
Kubis bunga
0.4
0.7
0.95
0.9
0.8
0.7
Bawang Mer
0.4
0.7
0.95
0.85
0.75
0.8
Kacang Panj
0.3
0.7
1.05
0.65
0.25
0.7
Ubi Jalar Ubi kayu Talas bentul Semangka Kangkungd
Tanaman
CROP Initial
C develop
WATER STAGES
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 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 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 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 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 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) 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) = (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 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. 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 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 Preliminary Check Of System: (a) Malfunctioning
valves, (b) Sunken sprinkler heads, (c) Incorrect or nonrotation 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) ncorrect operating 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 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) 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 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 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 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
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 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 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. 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.
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