CHAPTER 1.

History and Development of Irrigation Worldwide

Irrigation

- artificial application of water to the land in order to fulfill the water requirements of the
crops throughout the crop period for the full nourishment of the crops
- should be supplied as soon as the moisture falls up to the optimum level
- process through which controlled amount of water can be supplied through artificial means
such as pipes, ditches, sprinklers
- objective is to help agricultural crop growth, landscape maintenance, reduce the effect of
inadequate rainfall

Purpose of Irrigation System

- Ensure enough moisture essential for plant growth.

- Provide crop insurance against short duration drought.
- Cool the soil and atmosphere to provide a suitable surrounding.
- Wash out or dilute harmful salt, chemicals of the soil.
- Reduce hazards of soil piping.
- Soften the tillage pan

History and Development of Irrigation

- Egypt and China developed better techniques when it comes to irrigation building irrigation
canals, dams, dikes, and water storage facilities
- Ancient Rome built Aqueducts to carry water from snowmelt in the Alps to cities and towns
in the valleys below

a. Mesopotamia (6000 BCE)

- major trails towards civilization and modernization as its main purpose was to protect
Mesopotamia, and other ancient civilizations to the threat of flooding
- its system had some major components like the canals, gated ditches, levees and gate
- it was a basin type which were opened by digging a gap in the embankment and closed by
placing mud back into the gap

b. Egypt (3000 BCE)

- the uncertain level of water flowing in the Nile was the main problem for Egyptian
agriculture
- the Egyptians constructed canals and irrigation ditches to harness the Nile river’s yearly flood
and bring water to distant fields based on their invented Calendar
- Egypt Calendar: Akhet (Inundation or Flood): roughly from September to January.; Peret
(Emergence or Winter): roughly from January to May; Shemu (Low Water or Harvest or
Summer): roughly from May to September
- Egyptians practiced a form of water management called basin irrigation where they
constructed a network of earthen banks, some parallel to the river and some perpendicular
to it, that formed basins of various sizes
- Regulated sluices would direct floodwater into a basin and sit till its saturated and the
remaining water would be drained off to a basin down-gradient or to a nearby canal, and the
farmers of the drained plot would plant their crops
- they constructed strategically placed gates to control the flow of water and expansive
reservoirs to store precious water supplies to have adequate reserve in case of drought
- shadoof, hand-operated device for lifting water
- nilometer, utilized to predict flood levels along the Nile River as it serves as early warning
system for ancient communities, alerting them when water levels were lower or higher than
normal

c. Persia (500 BCE)

- the irrigation technique was a long tunnel is dug into arid land that allows water from
underground aquifers to be accessed for use by the local population, supporting large
settlements in spite of hostile environmental condition
- the technique is called Qanat, similar to other aqueducts but they differ in the source of a
water supply as Qanat is from groundwater, rather than a lake, river, or spring
- Construction began by locating an alluvial fan to access groundwater.
- A deep "mother well" was dug to reach the water table, sometimes up to 300 meters.
- Ventilation shafts were installed along the route for air and to guide the diggers.
- Excavation started from the tunnel’s mouth, moving upstream toward the mother well.

d. Roman (300 BCE)

- Channel used to transport fresh water to highly populated areas
- made from a series of pipes, tunnels, canals, and bridges
- systems were built over a period of about 500 years, from 312 B.C.E. to C.E. 226
- most recognizable feature of Roman aqueducts may be the bridges constructed using
rounded stone arches
- Aqueducts were a vital aspect of society in ancient Rome, channelling fresh water from
remote sources to city centres

i. Famous aqueducts in ancient Rome

Pont Du Gard, Nimes (1st century)
- tallest aqueduct bridges in the world, the bridge runs over the Gardon River, and is an
incredible 48.8 meters high
The Aqua Virgo, Rome (19 BCE)
- one of the first aqueducts to bring water into the city of Rome
- built in 19 BCE by Marcus Agrippa but was renovated during the Renaissance to transport
80,000 cubic meters of fresh water into the Trevi Fountain
Aqua Alexandrina, Rome (208-235 CE)
- One of the last aqueducts to be built during the Roman Empire
- it is 22.4 kilometers in length and almost all of its construction is built on a long series of
arches above the ground
Aqua Claudia, Rome (38-54 CE)
- one of Rome’s greatest aqueducts
- Mainly underground, was 69 kilometers long and carried water at the impressive speed of
80 cubic feet per second
Valens Aqueduct, Istanbul (4th century CE)
- provided gallons of fresh water from the hills of Istanbul to the Byzantine and Ottoman
Empires. T
- longest aqueduct of the ancient world
 Aqueduct of Segovia, Spain (2nd half of the 1st century)
- was built during the second half of the 1st century, to supply water from the Frio River to
the city
- around 30 meters high, the aqueduct’s double-layer bridge looms over the city and
stretches out 800 meters across its horizon,

e. China (256 BCE)

- Dujiangyan is the oldest and only surviving non-dam irrigation system in the world
- Development of Dujiangyan was for flood control, stable strategic rear base for the national
reunification, and the development of water transport routes
- instead of building a dam, they harnessed the river using a new method at that time
- Yuzui (Fish Mouth Levee) > Located at a river bend, it divides the Minjiang River into inner
and outer streams; inner canal flows into the Chengdu Plain, while the outer canal drains
excess floodwater.
- the Feishayan (Flying Sand Weir) > Positioned to handle the sand-laden water, it connects the
inner and outer streams; It helps drain excess water and prevents silting, which could lead to
riverbanks breaking; Annual cleaning by workers ensures the system remains functional
- the Baopingkou (Bottle-Neck Channel) > Located at Yulei Mountain, it was chiseled open by
Li Bing's team over eight years; Its purpose is to divert and irrigate water into the Chengdu
Plain; During floods, it controls water levels, and excess water is discharged through
Feishayan to the outer river.

f. Incan Civilization (1200 AD)

- between 3000-1800 BC Incan civilization first began developing settlements in coastal and
highland regions of the Andes Mountain range in Peru
- aqueduct system of the Incan irrigated agricultural terraces and bring fresh drinking water
into the cities
- aqueducts built on the sides of mountains where collected water is distributed
- Incas utilized their mountainous surrounding to maximize the efficiency of their agriculture
and irrigation systems
-
g. Philippines (1000 AD)
- irrigated rice terraces in the mountains of north-central Luzon, Philippines, that were created
more than 2,000 years ago by the Ifugao people
- rice terraces are a series of stepped fields that stretch for miles, carved out of the
mountainside by hand using simple tools made of stone and wood

Modern Irrigation System

a. Sprinkler System
- water droplets are sprayed or sprinkled like raindrops over landscape through rotating
nozzles connected to pipelines
- pipelines are connected perpendicular to a main pipeline laid in the field.
- Useful for sandy soil and uneven land
- Protects plants/crops from extreme frost or temperature
- Fertilizer and insecticide can be applied through sprinkler system
- Helps with soil conservation
b. Drip System
- water flows through narrow pipes laid on the fields and drips through small holes (emitters)
directly at the place of plant roots
- no water waste as less water is lost to evaporation, runoff and wind
- Optimizes soil moisture, saving water
- Direct hydration of plant roots for plant health
- Inhibits weed growth since water is applied directly to plants, not spread around the field
- Bacterial growth is limited since area near plants is dry

c. Center Pivot Irrigation:

- Rotating sprinklers mounted on a central pivot irrigate circular areas.
- Commonly used in large-scale agriculture for uniform water distribution.
- Requires minimal labor and covers large areas.
- High initial investment; best suited for flat terrain.

d. Surface Irrigation
- Modern system operates under high pressure, using electric pumps or turbines.
- Consists of watersheds, pipelines, sprinkler heads, and water meters.
- Water is collected from rainfall or groundwater, then transported through pipes to sprinkler
heads for distribution.
- Water meters monitor usage by individual users.

e. Artificial Subsurface Irrigation:

- Multiple pipes are buried to distribute water below ground, directly to roots.
- Reduces evaporation and targets specific plants, enhancing water efficiency.
- Higher upfront costs but more profitable for certain crops.
- Provides significant water savings, especially in arid regions, and improves crop resilience
and yields during dry periods.
 - most of the countries with the most irrigated land are emerging or developing nation

Indira Gandhi Canal – the Largest Irrigation Canal in India

- Also known as the Rajasthan Canal, it is the largest irrigation canal in India.
- Located in Rajasthan’s arid Thar Desert and completed in 1987.
- The 649 km canal extends into Jaisalmer, Rajasthan, starting from the Harike Barrage in
Punjab.
- With a flow rate of 1133 cubic meters per second, it can irrigate 1.8 million hectares of land.

Tongjiyan Irrigation System

- Located in Southwest China’s Sichuan Province, it has the largest and longest-operating
movable weir in Chinese history.
- Currently irrigates nearly 35,000 hectares of land.
- Provides water for four counties in the cities of Chengdu and Meishan.
Central Valley Project

- One of the largest water storage and transport systems in the world.
- In years of normal precipitation, it stores and distributes about 20% of California's developed
water.
- Delivers over 7 million acre-feet of water annually to farms, cities, and the environment.
- Approximately 75% of the water is used for agricultural irrigation, supporting seven of
California’s top 10 agricultural counties.

Upper Pampanga River Integrated Irrigation System (UPRIIS)

- Covers over 100,000 hectares of highly productive rice paddies in Central Luzon, Philippines.
- Known as the ‘rice granary of the Philippines’ due to its significant rice production capacity.
- Managed by the National Irrigation Administration (NIA), it spans approximately 145,800
hectares, including key provinces like Nueva Ecija, Tarlac, Pampanga, and Bulacan.
- Recognized for its exceptional efficiency in achieving the highest rice output per hectare in
the country
- Designed to harness and distribute water resources from the Upper Pampanga River,
ensuring consistent access to water year-round, even during dry seasons.
- Empowers local farmers to increase yields, diversify crops, and adopt modern agricultural
techniques, contributing significantly to food security and the agricultural economy of the
Philippines.
CHAPTER II. Land Classification and Soil Condition

A. Land Capability
- a scientific method for assessing a land’s physical features, soil qualities, and management
practices
- primary goal is to assess the land's potential, capability, and suitability for optimal use
- helps to find out efficiency of land for particular uses and prevent improper use of land
which leads to erosion hazards and deterioration of land quality
- provide valuable information about the natural potential and limitations of the land

B. Land Capability Classification

Capability Classes
Land suited for cultivcation (Arable Land)
1. Class I
- Suited for a wide range of plants, including cultivated crops, pasture, range, woodland, and
wildlife.
- Nearly level terrain with a low risk of erosion from wind or water.
- Excellent water retention and either well-supplied with plant nutrients or highly responsive
to fertilizer inputs.
- Not prone to overflow (run-off) damage.
- Characterized as deep, fertile, easily workable, and productive, making them suitable for
intensive cropping.
- Require ordinary management practices to maintain soil fertility and structure

2. Class II
- Have moderate limitations on use and a moderate risk of damage.
- Can be cultivated with easily applied practices, but require careful soil management.
- Necessary to implement conservation practices to prevent degradation and improve air and
water relations during cultivation
- This type may require special pratices sucg as Soil-conserving rotation, water control devices
or special tillage methods. It could be Contour farming; Strip; cropping.Bund construction.;
Terracing.
- The limitations of this type are
> Gentle slopes,
> Moderate susceptibility to wind or water erosion
> Less than ideal soil depth
> Somewhat unfavorable soil structure and workability
> Slight to moderate salinity
> Occasional damaging overflows
> Permanent wetness, correctable by drainage
> Slight climatic limitations on land use and management.

3. Class III
- Subject to severe limitations for cropland use and have a high risk of damage.
- Can be regularly used for crops with good rotations and proper treatment.
- Require cropping systems that produce adequate plant cover to protect against erosion and
preserve soil structure.
- Need a combination of practices for safe farming, including
- Sustainable practices that enhance soil health.
- Techniques to reduce erosion while maximizing productivity.
- Suitable for certain crops and pasture, requiring more intensive management.
- Well-suited for less intensive agricultural activities, such as grazing or cultivating crops
tolerant of existing conditions.
- Limitations of Class III Soils:
> Moderately steep slopes.
> High susceptibility to water or wind erosion.
> Frequent overflow with some crop damage.
> Very slow permeability of the subsoil.
> Wetness or continuing waterlogging even after drainage.
> Shallow depths limiting the rooting zone and water storage.
> Low moisture-holding capacity.
> Low fertility that is not easily corrected.
> Moderate salinity or sodium levels.
> Moderate climatic limitations.

4. Class IV
- Greater restrictions on use compared to Class III, with more limited plant choices.
- Require careful management and present challenges in applying and maintaining
conservation practices.
- more suitable for grazing, forestry, or recreational uses rather than intensive agriculture.
- When farmed, may require specialized practices such as:
> Contour farming.
> Terracing to manage erosion and improve productivity.
> Should predominantly be used for hay or sod crops for extended periods; row
crops should be planted only occasionally.
> Farmers and land managers should adopt sustainable practices to enhance land
health, reduce environmental impacts, maintain soil integrity, and promote biodiversity.
- Limitations of Class IV Soils:
> Steep slopes.
> Severe susceptibility to water or wind erosion.
> Severe effects of past erosion.
> Shallow soils.
> Low moisture-holding capacity.
> Frequent overflows leading to severe crop damage.
> Excessive wetness with ongoing risk of waterlogging after drainage.
> Severe salinity or sodium levels.
> Moderately adverse climate conditions.

Land Limited in Use Generally Not Suited to Cultivation (Non-Arable Land)

5. Class V
- Have limitations that restrict the types of plants that can be grown and prevent normal
tillage of cultivated crops.
- nearly level but may be wet, frequently overflowed by streams, stony, or subject to climatic
limitations.
- Cultivation of common crops is typically unfeasible; however, pastures can be improved with
proper management.
- Best suited for uses other than agriculture, such as:
- Wildlife habitat.
- Forestry.
- Recreational activities.
- Grazing should be regulated to maintain plant cover, allowing for limited grazing or foraging.
- Management should focus on conservation and preservation, protecting the natural
ecosystem and preventing degradation.
- Sustainable practices can help maintain biodiversity and enhance the health of surrounding
areas.

6. Class VI
- Should be used for grazing and forestry; they have moderate permanent limitations and are
unsuitable for cultivation.
- Focus on conservation and ecological preservation.
- Aim to maintain natural ecosystems and protect against further degradation.
- Implement sustainable practices to support biodiversity and safeguard the surrounding
environment
- Reserved for non-agricultural uses such as:
> Wildlife habitat
> Forestry.
> Recreational activities.
> May support limited grazing, but intensive agricultural practices are generally
impractical.
> Grazing should be managed to prevent destruction of plant cover.
- Exhibit continuing limitations that cannot be corrected, including;
> Steep slopes.
> Severe erosion hazard.
> Stony texture with shallow rocks.
> Shallow rooting zone.
> Excessive wetness or overflow.
> Low moisture capacity.
> Salinity or sodium issues.
> Severe climate conditions.

7. Class VII
- Physical conditions make it impractical to apply pasture or range improvements such as
seeding.
- Prioritize conservation and ecological preservation.
- Implement erosion control measures and maintain vegetation cover.
- Protect natural ecosystems to sustain local flora and fauna.
- Limit human activity in sensitive areas to mitigate environmental impacts and promote
ecological recovery.
- Soil restrictions are more severe than in Class VI due to continuing limitations that cannot be
corrected, including:
> Very steep slopes.
 > Erosion issues.
> Shallow soil.
> Presence of stones.
> Wet soil conditions.
> Salts or sodium issues.
> Unfavourable climate conditions.

8. Class VII
- often severely degraded or may not exist at all, making it nearly impossible for vegetation to
establish and thrive.
- requires careful stewardship to maintain its ecological integrity and ensure the health of the
surrounding environment.
- These limitations are often irreversible and can stem from
> Erosion or erosion hazards.
> Severe climatic conditions.
> Wet soil conditions.
> Presence of stones.
> Low moisture capacity.
>Salinity or sodium issues.
- Unsuitable for crops, grasses, or trees but may provide benefits for:
> Wildlife
> Watershed protection.
> Recreation

C. Soil Characteristics
- Incompatibility of water and soil adverse effect on the chemical and physical properties of
the soil
- basic understanding of soil/water/plant interactions will help irrigators efficiently manage
their crops, soils irrigation systems and water supplies
-
1. Physical Properties of Soil
a. Soil Texture
- determined by the size and type of solid particles that make up the soil that is
dependent on the relative proportions of mineral components like sand, silt, and clay
- e texture of a soil affects the flow of water, aeration of soil, and the rate of chemical
transformation all of which are important for plant life
 - using the triangle, users can plot the percentages of the components and identify
the specific soil texture class

b. Soil Structure
- refers to the grouping of particles of sand, silt and clay into larger aggregates of
various sizes and shapes
- proportions of solids and voids in a soil, which influence its density, porosity,
drainage, aeration, water-holding capacity and resistance to erosion

c. Soil Depth
- refers to the thickness of the soil materials that provide structural support, nutrients
and water for plants
- important factor that can affect plant growth, crop yield, and soil fertility

d. Soil permeability and Infiltration

- measure of the ability of air and water to move through soil which influenced by the
size, shape and continuity of the pore spaces,
- it is dependent on the soil bulk density, structure and texture
- Infiltration is the downward flow of water from the surface through the soil

e. Soil Color
- soil color provides information about the organiz composition of soil
- the darker the soil is, the more organic matter it contains

2. Chemical Properties
a. Cation Exchange Capacity (CEC)
- Cation exchange capacity refers to the maximum amount of total cations that a soil
sample can hold at a specific pH.
- It serves as an indicator of soil fertility, nutrient retention, and the soil's ability to
protect groundwater from cation contamination.
 b. Soil pH
- Soil reactivity is expressed in terms of pH, determining the soil's acidity and alkalinity.
- Soil pH measures the hydrogen ion concentration in the aqueous solution, typically
ranging from 3.5 to 9.5.
- Soils with high acidity usually contain elevated amounts of aluminum and
manganese, while alkaline soils have higher concentrations of sodium carbonate.
- Generally, agricultural production tends to be more successful in acidic soils

c. Soil Salinity
- Salts in the soil are transported from salt tables through water resources and
accumulate due to evaporation.
- Soil salinization can also occur during irrigation, often from drainage.
- The accumulation of salts affects the degradation of organic matter and the
vegetation on the soil.
- Common salts found in soil include magnesium sulfate, potassium sulfate, and
carbonate.

D. Basic Soil-Water Relationship

- Soil-water relationships are crucial for understanding water movement and availability in
soils
- many biological and chemical reactions occurring due to the presence of moisture in the soil.
- Moist soil, many reactions occur
- Very wet soil, different sets of reaction occur
- behavior of a soil is completely altered once the moisture or saturated conditions are
specifically dependent upon soil texture and structure
- the voids in between the soil mass is filled with air or water
a. Void Ratio, e
- ratio between the volumes of voids to the volume of solids of a soil mass
- parallel with soil porosity, the value depends on the consistence and packing of the soil

-
-
- directly affected by compaction

b. Porosity, n
- ratio between the volumes of voids to the total volume of a soil mass
- pore space both contains and controls most of the functions of soil

c. Relationship between e and n

- relationship of these two shows that as void ratio increases, porosity also increases,
indicating more void space relative to the solid particles

-
d. Water Content or Moisture Content, MC or
- ratio of the weight of water to the weight of the solid particles
- amount of water presents relative to the weight of the dry soil solids
- measurement is crucial for understanding soil behavior, influencing plant growth, and
guiding irrigation practices

-
-

e. Degree Saturation, S
- ratio of the volume of water to the volume of voids
- refers to the amount of water that fills the pores spaces in the soil
- can be occasionally expressed as percentage and occasionally not
- determines the actual relationship between the weight of moisture present in a space were
saturated, is the most significant factor in the design of structures

f. Specific Gravity for Solids

- e ratio of the density of a solid material to the density of a reference substance, typically
water, at a specified temperature
- s essential for calculating other soil characteristics, such as void ratio and degree of
saturation, and plays a significant role in geotechnical engineering applications

g. Unit Weight of Soil Mass

- influences the design and stability of structures built on or within the soil
-
h. Dry Unit Weight
- defined as the dry soil particles per unit volume of soil.
- typically expressed in units like kN/m3 or kg/ m3
- helps in understanding the soil’s compaction and its load-bearing capacity, especially when
moisture content varies

-
i. Saturated Unit Weight
- defined as the weight of a saturated soil mass divided by its total volume
- it influences stability, bearing capacity, and drainage characteristics in geotechnical design

-
E. Measurement of Soil Moisture
1. Direct Method
a. Gravimetric Method/Oven Drying Method
- an apparatus wherein soil sample is collected in a moisture can and wet weight of the
sample is recorded

b. Volumetric Method
- measurement where soil sample is taken with a core sample or with a tube auger
whose volume is known
2. Indirect Method
a. Tensiometer
- sealed, airtight, water-filled tube (barrel) with a porous tip on one end and a vacuum
gauge on the other
- measures soil water suction (negative pressure), which is usually expressed as tension
- it must be installed properly so that the porous tip is in good contact with the soil,
ensuring that the soil-water suction is in equilibrium with the water suction in the tip
- The suction force in the porous tip is transmitted through the water column inside the
tube and displayed as a tension reading on the vacuum gauge

b. Gypsum block
- an electrical resistance blocks consist of two electrodes enclosed in a block of porous
material.
- electrodes are connected to insulated lead wires that extend upward to the soil surface
- Resistance blocks work on the principle that water conducts electricity
- As the soil moisture changes, the water content of the porous block also changes
- The block's resistance can be related to the water content of the soil by a calibration
curve

c. Neutron Probe
- an apparatus where soil moisture can be estimated quickly and continuously with
neutron moisture meter without disturbing the soil
- soil moisture can be estimated from large volume of soil
- Moisture content of the soil can be known from the calibration curve with count of
slow neutrons.
- consists of a probe and a scalar or rate meter

d. Pressure Plate and Pressure Membrane Apparatus

- generally used to estimate field capacity, permanent wilting point and moisture content
at different pressure
- apparatus consists of an air tight metallic chamber in which porous ceramic pressure
plate is placed
CHAPTER 3. Irrigation Water

I. SOURCES AND STORAGE OF IRRIGATION WATER

Irrigation

• method of supplying water to crops artificially to meet their water needs

• artificial application of water to the soil though various systems of tubes, pumps,
and sprays
• usually used in areas where rainfall is irregular or dry times or drought is
expected
• about 70 percent of all the world's freshwater withdrawals go towards irrigation
uses

Sources of Irrigation Water

1. Groundwater from Wells

- well water is drawn from underground aquifers by drilling a well and
installing a pump to bring the water to the surface
- water in wells is untreated, meaning it may contain contaminants like
bacteria, heavy metals, or chemicals
- factors such as rainfall, soil composition, and seasonal changes can affect the
consistency of the water supply
- regular testing and treatment are necessary to ensure well water is safe for
drinking and household use

2. Surface Water
- common and accessible water source for irrigation systems
- refers to any body of water that is above ground, such as rivers, lakes,
streams, ponds, and oceans
- forms from precipitation, runoff, and groundwater that rises to the surface
- crucial source for drinking water, agriculture, industry, and recreation, but it
is also more vulnerable to contamination from pollutants like agricultural
runoff, industrial waste, and urban stormwater

3. Drainage Ponds
- artificial basins designed to manage stormwater runoff
- collect excess rainwater from urban areas, such as roads, parking lots, and
rooftops, to prevent flooding and reduce erosion
- help filter out sediments and pollutants before the water returns to natural
waterways

4. Rainwater
- collected from rooftops, impermeable surfaces, or through catchment
systems and stored in tanks or reservoirs for later use
- appropriate filtration and treatment is needed as it can be used for drinking,
household purposes, irrigation, and even industrial applications
- helps reduce demand on groundwater and municipal supplies
 5. Municipal Water
- water that’s treated and monitored provided by the local government or a
public utility company
- readily available and easily accessible as it is supplied consistently and in
sufficient quantities
- may have fluoride and/or chlorine added at rates and sometimes sodium
compounds are added to treat hard waters.
- cost is higher compared to other sources

Storage of Irrigation Water

1. Dam
- a man-made obstruction placed across a river or stream to to retain or
restrict the flow of surface water or underground streams
- reservoir crated by dams not only to suppress floods but also provide water
for activities such as irrigation, human consumption, industrial use,
aquaculture, and navigability

2. Embankment
- either a man-made or naturally-formed wall on the side of a river that
ensures flooding does not occur
- constructed using earth, rocks, or other materials and are designed to
withstand the pressure of rising water levels
- help manage erosion by stabilizing the riverbanks and protecting nearby
infrastructure or farmland

3. Pit
- dug-out area that retains water to hold rainwater, runoff, or water from
other sources, providing a reliable supply for irrigation in areas with limited
availability.
- conserves water by storing it until needed for crop irrigation
- simpler and less costly to construct

II. Flow Through Soil

1. Loam Soil
- has coarse sand, tiny silt particles, and clay in equal amounts
- allows plants to grow roots easily and provides good drainage without drying
out

2. Clay Soil
- is sticky and made of very small sediment that packs together tightly
- difficult for a plant’s delicate roots to penetrate and hard for water to sink in

3. Sandy Soil
- gritty and light colored because it lacks humus
- made of tiny pieces of rock and sand and allows water to drain easily
delivering nutrients to plants
 Water flow through soil

- essential to study to optimize crop growth, conserve water resources, and

prevent soil degradation
- soil-water interaction directly influences the design and operation of
irrigation systems

Infiltration

- downward entry of water into the surface of soil and rock

- faster movement of water
- infiltration rate is the rate at which the soil absorbs water measured in
inches/millimeters per hour. Infiltrometer is used to measure this rate.
- infiltration capacity refers to the maximum amount of rainwater that can
enter the ground in a given time

Percolation

- occurs underground and its downward movement of water is through soil

and rock
- after infiltration, water starts to move downward through the soil and rock
passing different layers of the ground

Lateral Flow

- movement of water under gravitational forces parallel to the slope of the

land
- if the soil becomes saturated or if there is an impermeable layer, water may
move laterally (sideways) through the soil
- waterlogging is the result when soil is heavily saturated or impermeable later
is too close to surface
- groundwater recharge refers to the process of water moving downward to
replenish the groundwater reservoir, typically originating from precipitation
that infiltrates the subsurface and percolates towards the water table

III. Irrigation Wells

- man-made hole or excavation in the ground that is designed to access and
extract water from underground sources, such as aquifers
- aquifer is a body of rock and/or sediment that holds groundwater
- constructed by drilling or digging deep into the earth until the water-bearing
layer is reached.
Types of Water Wells

A. Tube Wells
- uses a long 100–200 millimetres stainless steel tube or pipe is boreding the
ground
- classified on the basis of the entry of water into the well, the method of
construction, the depth and the type of aquifer tapped

a. Based on Entry of Water

i. Screen well
- filter out sediments and allow water to enter the well
- flow is radial
- area of flow is increased by increasing the length of strainer pipe
- strainer well, consists of a perforated or a slotted pipe with a wire mesh
wrapped around the pipe with smaller annular space between the two
placed against the water bearing stratum
- slotted well, uses a slotted pipe without being covered by any wire mesh
- other strainer wells are Louver Type Screen, Coir-Rope strainer, bamboo
strainer, agricultural strainers. Discussed below are the two types of screen
well

ii. Cavity Type

- a shallow well that can reach depths of up to 10 to 15 meters but also
depends on local geological conditions and the water table level
- designed to tap into the upper aquifer layers and are often used for irrigation
and domestic water supply
- draws water from bottom of the well and not from the sides
- flow is spherical
- area of flow is increased by enlarging the size of cavity
- requires a strong and dependable stratum immediately on top of the water
bearing stratum

b. based on method construction

i. drilled tube well
- are vertical shafts created to access groundwater from deeper aquifers
ranging in depth from 50 to 300 meters. methods of drilling: Rotary and
Cable tool
- rotary, rotating drill stem; drilling fluid or air is circulated down through the
drill stem in the hole and back to the surface to remove cutting
- cable, constructed by lifting and dropping heavy drill bit in the bore hole;
resulting loose material, mixed with water, is removed using a bailer or sand
pump; also called percussion drilling

ii. Driven Tube Wells

- series of connected lengths of pipe driven by repeated impacts in the ground
to below the water table
 - constructed by driving a small-diameter pipe into shallow water-bearing
sand or gravel
- can tap only shallow water and are easily contaminated from nearby surface
sources because they are not sealed with grouting material
- best suited for domestic supplies, for temporary water supplies, and for
exploration and observation
- can be constructed in a short time, at a minimum cost, and even by one
person

iii. Jetted Tube Wells

- utilizes a jet pump that forces water through a pipe, creating a high-pressure
jet that displaces soil and sediment, allowing the well to be drilled deeper
depths of 10 to 15 meters
- effective in areas with loose, unconsolidated soil where shallow groundwater
sources are accessible
- have only small yields and the portability of the equipment

c. based on depth
i. shallow tube wells
- low capacity; cavity and strainer are examples of this
- good for stability of their walls but recharge is usually slow
- shallow wells in sandy formation collapse easily
- water is of better quality
- dry quickly in protracted dry season
- Easy water pollution due to poor disposal of human and industrial waste

ii. Deep wells

- high capacity, tapping more than one aquifer

d. based on aquifer characteristics

i. water table wells
- vertical shafts drilled into the ground to access groundwater from aquifers, 5
to 25 meters deep
- used in agriculture
- easier and less expensive to install compared to deeper wells
- vulnerable to pollutants, such as fertilizers and pesticides

ii. artesian wells

- drilled into confined aquifers where water is under natural pressure,
allowing it to rise to the surface without pumping
- range from 50 to 200 meters in depth
- trapped between impermeable rock or clay layers creating pressure that
pushes the water upward
- suitable for regions with pressurized aquifers where water can flow naturally
to the surface
 iii. borewells in hard rock areas
- deep, narrow wells ranging from 50 to over 500 meters in depth
- used in urban areas, water-scarce regions, and rocky terrains, where deep
aquifers provide a reliable water source
- offer a steady, year-round water supply and are less prone to surface
contamination

iv. skimming wells

- e shallow wells designed to extract water from the top layers of an
unconfined aquifer, 5 to 15 meters in depth
- used in areas where saline water is present at deeper levels, allowing only
fresh water from the top layers to be skimmed off
- most suitable in coastal areas, riverbanks, or regions with a shallow water
table where deeper water may be brackish or salty
- limited in their ability to provide large volumes of water and affected by
seasonal fluctuations in the water table

B. Open Wells
- major means of domestic water supply
- shallow and usually tap water table aquifers
- tap ground water in hard rock areas
- serve as a reservoir for groundwater slowly replenishing the well
- do not require sophisticated equipment and skilled personnel for
construction
- large space is required by the well structure
- construction of wells is slow and laborious

a. Open Wells in Unconsolidated Formation

i. Unlined wells
- sides of the wells are not protected, no lining because for temporary use
only
- to ensure stability, the depths of unlined wells are limited to about 6.5 m
 ii. Wells with previous lining
- lined with dry bricks or stone masonry
- water flows from the surrounding aquifer into the wells through the sides of
the well
- annular hollow space around the well lining will be self-sealing in loose
formations
- allows for effective water flow while maintaining structural integrity

iii. wells with impervious lining

- deeper than previous wells but does not exceed 30m
- exceeding depths are uneconomical and costly
- used in alluvial formations

iv. dug-cum-bore wells

- hydraulically superior to ordinary dug wells
- it drills small diameter holes of sizes ranging from 7.5 to 15 cm in diameter,
through the bottom extending them up to water bearing formation
underneath the bottom of the dug well
- first type of bore, bore extends to the top of the water bearing formation,
where a cavity is formed
- second type of bore, well screens are laid opposite the water bearing
formations and blind pipes provided opposite the non-water bearing strata

b. open wells in hard rock foundation

i. dug wells
- usually open, excavated pits through the rock, and lined only a couple of
meters
- pneumatic rock blasting equipment, using jack-hammers and explosives, is
employed for the excavation of the well through hard rocks

Aquiclude: A saturated but relatively impermeable material that does not yield appreciable
quantities of water to wells; clay is an example.
Aquifuge: A relatively impermeable formation neither containing nor transmitting water; solid
granite belongs in this category.
Aquitard: A saturated but poorly permeable stratum that impedes groundwater movement and does
not yield water freely to wells, that may transmit appreciable water to or from adjacent aquifers and,
where sufficiently thick, may constitute an important groundwater storage zone; sandy clay is an
example.
IV. Pumping Water for Irrigation and Drainage
A. Types of Pumps for Irrigation and Drainage
1. Centrifugal Pumps
- transports liquids
- extremely versatile, can operate on dry land or under water, and are able to
pump large volumes of water against high levels of resistance
- design > prevents them from being submerged hence are kept outside the
water-body; parts are nozzles, casing, bearing housing and impeller and
shaft are the rotating parts
- installation > ground near the source of water
- working principles > transforms the centrifugal force into kinetic energy in
order to drive the water out; energy generated through the rotation of the
impeller drives the water out with the help of a diffuser

2. Submersible Pumps
- located under water and don’t need to be primed before first use
- don’t need to suck the water up from an irrigation lake
- can lift water from deep wells by pumping out larger solids or grinding them
into smaller particles, as well as moving wastewater at higher pressures and
flow rates
- widely used in mining, the Navy, rescue missions, and wastewater services
- the energy being used purely to push the water from the outlet pipe
- since fully submerged, these are less prone to damage from environmental
factors like weather, debris, or temperature fluctuations, making them highly
durable for long-term use

3. Positive Displacement Pumps

- add energy to a fluid by applying force to the liquid with a mechanical device
such as a piston or plunger
- decreases the volume containing the liquid until the resulting liquid pressure
equals the pressure in the discharge system
- provide a constant flow of fluid at a given pump speed, regardless of the
discharge pressure required
- used for highly viscous working fluids, high pressure low flow conditions,
high efficiency, self-priming, precise metering

4. Solar-powered Pumps
- powered by solar panels, uses energy from the sun to power the pump,
offering an eco-friendly and cost-effective alternative to traditional diesel or
electric pumps
- two types of SPP: Submerged and Surface Solar Pumps
B. Choosing the Right Pump
Steps to choose the right pump
- Identify the Fluid: kind of fluid consider viscosity, temp and its contents.
- Define the Flow Rate and Pressure: required flow rate and discharge
pressure; high flow rates and low pressure use centrifugal; low flow rates
and high pressure use positive displacement pumps
- Check the Installation Location: where it operates, surface of submerged
- Power source: check if electrical or solar power is available
- Consider Efficiency

Thus,

- Use a positive displacement pump for high pressure, viscous fluids, and
precision control.
- Use a centrifugal pump for high flow rates and low-viscosity fluids.
- Use a submersible pump for deep or submerged pumping applications, like
wells or flooded environments.
- Use surface solar pumps in off-grid, remote areas with a need for sustainable
and energy-efficient pumping solutions

V. Quality of Irrigation Water

A. Irrigation Water Quality
- refers to chemical composition of the water, or more specifically, to the
mineral composition of water
- physical and biological properties determine the suitability of the water for
irrigation
- quality criteria for irrigation is different from drinking water, its quality
criteria vary among crops

B. Properties of Irrigation Water Quality

The following determines the suitability of irrigation as it influences the soil health, plant
growth, and the long-term sustainability of agricultural practices.
a. pH d. Alkalinity
b. Salinity e. Sodium Adsorption Ratio (SAR)
c. Hardness f. Concentration of specific minerals

a. Irrigation Water Ph
- influences the solubility of mineral salts
- Acidic Water (pH < 7): Can lead to nutrient availability issues, affecting
plants' ability to absorb essential minerals like calcium and magnesium
- Alkaline Water (pH > 7): May cause nutrient deficiencies, particularly for iron
and manganese, and can lead to the buildup of salts in the soil.

b. Water Salinity
- concentration of dissolved salts, primarily sodium, calcium, magnesium, and
chloride
- affect soil structure, plant health, crop yields and also reduces the plant’s
ability to absorb water
 - measured as TDS (Total Dissolved Salts) or as electrical conductivity (EC)
which relates to total concentration of dissolved salts in the water

c. Water Hardness
- sum of the concentrations of calcium and magnesium in the water,
expressed as ppm (parts per million) of CaCO3
- when water hardness that is too high, precipitation of calcium and
magnesium salts might occur in the irrigation system, damage it or reduce its
efficiency
- when hardness that is too low might cause corrosion in the irrigation system

d. Alkalinity
- measure of the ability of the water to resist changes in pH
- high alkalinity often corresponds with a higher pH level while low alkalinity is
associated with lower ph level
- important irrigation water quality parameter

e. Sodium Absorption Ratio

- also known as sodium to calcium and magnesium ratio is an irrigation water
quality parameter that helps to estimate the potential of sodium in the
water to adsorb to soil particle in relation to calcium and magnesium

-
- All concentrations are expressed in meq/L

f. Concentration of Specific Elements

- different crops all have different susceptibilities to certain elements as a
result, the suitability of water for irrigation often depends on the specific
crop being grown
C. Mineral Composition of Irrigation Water
- natural water sources can affect the suitability of water for irrigation
- high concentrations of certain salts may lead to soil salinity, nutrient
imbalances, and reduced plant growth, while others are necessary for
proper plant development
 VI. Salts Problems in Water and Soil
A. Salinity
1. Types of Salinity
a. Primary Salinity - is produced by natural processes such as the deposit of salt by rain and
wind or the weathering of rocks that occur over thousands of years.
b. Secondary Salinity - additional salt that is being transferred to the soil or the water’s
surface. This occurs with widespread land removal and altering the usage of land.

2. Effects of Salinity
- Poor health of native vegetations and also leads to death of plants.
- Reducing the yield of crops by harming the growth and health of salt
intolerant crops

B. Salt Problem in Water

- salinization is the process in which soil that is low in salt becomes high in
salt, it negatively impacts the development of plants and induces land
degradation

a. Causes of soil salinization

- High evaporation rates
- Poor drainage or waterlogging
- Irrigation with salt-rich water
- Sea-level rise when sea salts seep into the land
- Inappropriate use of fertilizers.

b. Indicators of Soil Salinity

- Plant withering
- Crop loss
- Appearance of salt-tolerant plants in the area

c. Preventing Soil Salinization

- Optimize irrigation
- Using cover crops to protect the ground surface
- Restrain from deep tillage so that soil salts with not be transferred to root
zones

Capability Subclasses

- groups of capability units within classes that have the same kinds of
dominant limitations for agricultural use as a result of soil and climate
1. Subclass (e) - Erosion Risks
- Soils primarily at risk of erosion.
- Susceptibility to erosion and past erosion damage are the main factors for
classification.
- Implement erosion control measures.
- Use practices like cover cropping, contour farming, or terracing.
2. Subclass (w) - Excess Water
- Soils with excess water as the dominant limitation.
- Criteria include poor drainage, wetness, high water table, and overflow.
- Implement drainage systems to remove excess water.
- Choose crops tolerant of wet conditions or utilize water management
techniques.

3. Subclass (s) - Rooting-Zone Limitations

- Soils with limitations affecting the rooting zone, such as:
- Shallowness of rooting zones.
- Presence of stones or rocky texture.
- Low moisture-holding capacity.
- Low fertility that is difficult to correct.
- High salinity or sodium levels.
- Enhance soil depth and quality with amendments or conservation tillage.
- Select crops that thrive under shallow or poor soil conditions.
s
4. Subclass (c) - Climatic Limitations
- Soils where climate factors (temperature, wind, humidity, moisture
availability, sunlight) are the primary limitations.
- Adapt management practices to climate conditions.
- Select drought-resistant crops or adjust planting times.