introduction to irrigation engineering
TRANSCRIPT
NUMAN MIZYED
AN-NAJAH NATIONAL UNIVERSITY
Agricultural Practices and Irrigation
Agricultural practices with significant environmental impacts
Irrigation
Fertilization
Pesticides, insecticides and herbicides application
Agricultural Activities
Agricultural activities:Irrigation, fertilization, agro-chemicals, ag. machinery
Soil root zone:Root growth, biological activities,Nitrification, de-nitrification ..etc
Impacts on groundwater: quality, quantity
Impacts on crops, Agricultural workersHuman health and Consumers of productsRunoff to surface water
Impacts on soil:Compaction, hard pansIncreasing salinityDegradationErosion
IRRIGATION IS THE APPLICATION OF WATER TO THE SOIL FOR THE PURPOSE OF SUPPLYING THE MOISTURE
ESSENTIAL FOR PLANT GROWTH
Irrigation
Historical perspectives
Ancient civilizations rose over irrigated areas
Egypt claims having the world's oldest dam, 108m long, 12m high, built 5,000 years ago
6,000 years ago, Mesopotamia supported as many as 25 million people.
The same land today with similar population depends on imported wheat for food
Challenges for Irrigation
Depletion of natural resources (soil and water)
Salinization of soil
Lower productivity of soil: tax records from Mesopotamia barely yields were 2500L/ha, now only ¼ to ½ this value.
Desertification
Irrigation & technology
Hi-tech control: tensiometers, controls and automation of irrigation and water application.
Use of remote sensing for irrigation scheduling and prediction of yield
New job opportunities
Purposes of Irrigation
Providing insurance against short duration droughts
Reducing the hazard of frost (increase the temperature of the plant)
Reducing the temperature during hot spells
Washing or diluting salts in the soil
Softening tillage pans and clods.
Delaying bud formation by evaporative cooling
Promoting the function of some micro organisms
Sources of Moisture for Plant Growth
Precipitation (includes rain, hail, snow):Frequency
Intensity
Depth
• Atmospheric water
• Flood water
• Ground water
Crop processes requiring water
Digestion
Photosynthesis,
Transport of minerals and photosynthesis,
Structural support,
Growth, and
Transpiration.
Evapotranspiration (ET).
More than 99% of water added to the plant is lost through transpiration
Water is lost from soil surfaces through direct evaporation
Evaporation and transpiration can't be separated easily.
Crop consumptive use versus evapotranspiration.
Factors affecting evapotranspiration
Climatic factors: Such as temperature, solar radiation, wind speed, humidity, precipitation.
Crop type.
Crop growth stage,
Available water in the soil. More energy is required to extract water from dry soil.
Measurements of Evapotranspiration
Rising Up Of Salts15
Salt Accumulation In Furrow Irrigation
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Salt Accumulation In Furrow Irrigation
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Drip Irrigation18
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Salinity Accumulated On The Border Between The Wet To Dry
Zones In Drip Irrigation
Saline Spots Created By Subsoil Drip Irrigation
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Distribution Of Salts In Soil As Influenced By Different
Irrigation System 21
Soil Type And Water Movement. The application Of Water Is By
Drippers22
LeachingLeaching consist of applying irrigation water in excess of the soil moisture depletion level to remove salts from the root zone. The excess water flows down below the root zone, carrying salts with it.
The leaching requirement is the leaching fraction (the amount of excess water) needed to keep the root zone salinity level within that tolerated by the crop. This requirement is determined by the crop`s tolerance to salinity and by the salinity of the irrigation water.
This excess, water expressed as a percent of the applied irrigation water, is the leaching fraction.
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Water Balance At The Root Zone
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Salt and Water Balance
Water balanceDepth of irrigation water = ET + Depth of drainage water
Diw = ET + Ddw
Salt balanceDiw * Eciw =Ddw * Ecdw
LF= Eciw/Ecdw = Ddw/Diw
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Roots Distribution And Water Use Affected By Depth
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Selection of irrigation systems
Water source and value of water
Cost of pumping and whether pumping is available or not.
Available cost of the system (the available capital).
Type of soil and its topography.
Type of crops.
Irrigation systems
Gravitational methods: surface systems
Pressurized systems:Sprinklers
Trickle systems
Surface systems
AdvantagesHigh flow rates
Low cost
No pumping
DisadvantagesLow efficiency
Erosion, leveling, operation, drainage
Not suitable for sandy soils and lands with high slopes
Types of surface irrigation
Uncontrolled or wild flooding
Border strip flooding
Basin irrigation
Furrow irrigation
Sprinkler irrigation
Soil too porous for good distribution of water (sandy soils).
Topography as in hilly areas where the use of surface irrigation will result in erosion and low efficiency.
Irrigation stream too small to use surface systems.
Labor is not experienced with surface irrigation.
Spacing between crops is too small which will require a lot of drip lines
Classification of sprinkler systems:
Solid set systems
Move stop system
Continuous move systemsCenter pivot systems
Linear move systems
Big gun systems
Trickle Irrigation
Trickle Irrigation
AdvantagesSaving water
Saving energy – low pressure
Yield is higher than other systems when water with higher salinity is used
• DisadvantagesHigh cost
Salinization of soil between rows
Future perspectives and challenges
Use of marginal water:Brackish water
Treated wastewater
Intensive agricultureIncreasing productivity per unit area
Organic farming