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Lecture 7B: Micro-Irrigation System Drip and Sub Drip Irrigation Prepared by Husam Al-Najar The Islamic University of Gaza- Civil Engineering Department Irrigation and Drainage- ECIV 5327

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  • Lecture 7B: Micro-Irrigation System

    Drip and Sub Drip Irrigation

    Prepared by

    Husam Al-Najar

    The Islamic University of Gaza- Civil Engineering Department

    Irrigation and Drainage- ECIV 5327

  • Micro- irrigation

    • Delivery of water at low flow rates through various types of water

    applicators by a distribution system located on the soil surface, beneath

    the surface, or suspended above the ground

    توصيل المياه بمعدالت تدفق منخفضة من خالل أنواع مختلفة من أجهزة تطبيق المياه عن طريق نظام •

    توزيع يقع على سطح التربة أو تحت السطح أو معلق فوق سطح األرض

    • Water is applied as drops, tiny streams, or spray, through emitters,

    sprayers, or porous tubing

    يتم تطبيق الماء على شكل قطرات أو تيارات صغيرة أو رذاذ من خالل بواعث أو رشاشات أو أنابيب •

    مسامية

  • Water Application Characteristics of Micro- irrigation

    خصائص تطبيق المياه

    Low rates معدالت منخفضة

    Over long periods of time على مدى فترات طويلة من الزمن

    At frequent intervals على فترات متكررة

    Near or directly into the root zone بالقرب من منطقة الجذر أو مباشرة

    At low pressure عند ضغط منخفض

    عادة الحفاظ على نسبة عالية من الماء

    نسبياUsually maintain relatively high water content

    / تستخدم في المحاصيل الزراعية

    البستانية ذات القيمة األعلى وفي المناظر

    الطبيعية والمشاتل

    Used on higher value agricultural/horticultural

    crops and in landscapes and nurseries

  • كفاءة تطبيق عالية

    High application efficiency

    High yield/quality جودة عالية/ عائد

    Decreased energy requirements انخفاض متطلبات الطاقة

    Reduced salinity hazard تقليل مخاطر الملوحة

    Adaptable for chemi-gation قابل للتكيف مع المعالجة الكيميائية

    Reduced weed growth and disease انخفاض األعشاب الضارة ومشاكل المرض

    problems

    Can be highly automated يمكن أن يتم تشغيله بنظام التشغيل الذاتي

    Advantages of Micro- irrigation

    مزايا الري الدقيق

  • High initial cost تكلفة أولية عالية

    Maintenance requirements (emitter .(انسداد الباعث ، إلخ)متطلبات الصيانة

    clogging, etc.)

    Restricted plant root development تقييد في تطور جذر

    على طول )تراكم الملح بالقرب من النباتات

    (حواف المنطقة المبللة

    Salt accumulation near plants (along

    the edges of the wetted zone)

    Disadvantages of Micro- irrigation

    مساوئ الري الدقيق

  • Salt Movement Under Irrigation with Saline Water

    Salt accumulation leached downward

    by successive water applications

    Salt accumulation leached radially

    outward from drip tubing

    Subsurface Drip Sprinkler/Flood

  • Types of Systems

    1. Surface trickle (drip)

    – Water applied through small emitter openings to the soil surface

    (normally less than 3 gal/hr per emitter)

    – Most prevalent type of micro-irrigation

    – Can inspect, check wetting patterns, and measure emitter discharges

  • 2. Spray

    – Water applied (spray, jet, fog, mist) to the soil surface at low pressure

    (normally less than about 1 gal/min per spray applicator)

    – Aerial distribution of water as opposed to soil distribution

    – Reduced filtration and maintenance requirements because of higher flow

    rate

  • 3. Bubbler

    – Water applied as a small stream to flood the soil surface in localized areas

    (normally less than about 1 gal/min per discharge point)

    – Application rate usually greater than the soil's infiltration rate (because of

    small wetted diameter)

    – Minimal filtration and maintenance requirements

  • 4. Subsurface trickle

    – Water applied through small emitter openings below the soil surface

    – Basically a surface system that's been buried (few inches to a couple feet)

    – Permanent installation that is "out of the way"

  • 76 cm

    152 cm

    Typical Subsurface Drip Tubing Installation for Row Crops

    30 – 35 cm

    Non Wheel-

    Track Row

    Wetting Pattern

    Drip Tubing

    152-cm dripline spacing is satisfactory on silt loam & clay loam soils

  • System Components

    • Pump

    • Control head

    – Filters

    – Chemical injection equipment (tanks, injectors, backflow prevention, etc.)

    – Flow measurement devices

    – Valves

    – Controllers

    – Pressure regulators

    • Mainlines and Submains (manifolds)

    – Often buried and nearly always plastic (PVC)

    • Laterals

    – Plastic (PE)

    – Supply water to emitters (sometimes "emitters" are part of the

    lateral itself)

  • Schematic of a Typical Micro-irrigation System

  • Applicator Hydraulics

    • General

    – Need pressure in pipelines to distribute water through the

    system, but the applicator needs to dissipate that pressure

    – qe = emitter discharge

    – K = emitter discharge coefficient

    – H = pressure head at the emitter

    – X = emitter discharge exponent

    (varies with emitter type)

    xKHe

    q

  • Emitter Hydraulics

    Emitter Type

    Coefficient, K - Exponent, X

    Emitter Discharge (Liter/minute)

    Operating Pressure (m)

    5.6 m

    8.4 m

    11.2 m

    Porous Pipe - 0.112 1.00

    9.0

    13.6

    18.2

    Tortuous Path 0.112 0.65

    3.3

    4.3

    5.2

    Vortex/Orifice 0.112 0.42

    1.7

    2.0

    2.2

    Compensating 0.112 0.20

    0.9

    0.9

    1.0

    xKHe

    q

  • Other Design and Management Issues

    • Clogging

    – Physical (mineral particles)

    – Chemical (precipitation)

    – Biological (slimes, algae, etc.)

    • Filtration

    – Settling basins

    – Sand separators (centrifugal or cyclone separators)

    – Media (sand) filters

    – Screen filters

  • Filtration Requirements for Drip Emitters

    Filter openings should be 1/7th –

    1/10th the size of the emitter

    orifice

    0.020-inch orifice

  • Plugging Potential of Irrigation Water for

    Microirrigation

  • • Chemical treatment

    – Acid: prevent calcium precipitation

    – Chlorine

    • control biological activity: algae and bacterial slime

    • deliberately precipitate iron

    • Flushing

    – after installation or repairs, and as part of routine maintenance

    – valves or other openings at the end of all pipes, including laterals

    • Application uniformity

    – manufacturing variation

    – pressure variations in the mainlines and laterals

    – pressure-discharge relationships of the applicators

  • Advantages of Subsurface Drip Irrigation

    • High water application efficiency

    • Uniform water application

    • Lower pressure & power requirements

    • Adaptable to any field shape

    • No dry corners (vs. center pivot)

    • Adaptable to automation

  • Disadvantages of Subsurface Drip Irrigation

    • High initial cost

    • Water filtration required

    • Complex maintenance requirements

    – Flushing, Chlorination, Acid injection

    • Susceptible to gopher damage ( القوارض)

    • Salt leaching limitations

  • Schematic of Subsurface Drip Irrigation (SDI) System

    Pump

    Station

    Backflow

    Prevention

    Device

    Flowmeter

    Chemical

    Injection

    System

    Air & Vacuum

    Release Valve

    X X

    Pressure Gage

    X X

    Flush Valve

    X X

    Dripline

    Laterals

    Zones

    1 and 2

    Submain

    Flushline

    Filtration

    System

    x

    X Zone Valve

  • SDI System Maintenance

    • Lateral flushing schedule (sediment)

    • Chlorine injection schedule (biological growths)

    • Acid injection schedule (chemical precipitates & scaling)

  • Trenching across the drip tubing ends for PVC manifold

    installation

  • Flush Risers on Distal End

    Ball Valve for Manual Flushing

    of Drip Laterals

    Air Vent to Release Trapped Air

    from Laterals

  • SDI Water Application Rates (mm/hr)

    (152 cm tubing spacing)

    cm30.5

    cm45.7

    cm61.0

    mm/hr

    0.60 Liter/hr 1.10 0.86 0.66

    0.78 Liter/hr 1.4 1.1 0.86

    1.24 Liter/hr 2.2 1.8 1.4

    2.0 Liter/hr 3.6 2.9 2.2

    Emitter Spacing

    Emitter Discharge 1

    52

    cm

    30.5 cm