introduction to irrigation engineering

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