lecture 7b: micro-irrigation system drip and sub drip...
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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