Irrigation Types and Storage Systems

Irrigation Types and Storage Systems

India’s Irrigation Statistics

• Total Land Area: 322 million hectares (mha)

• Cropped Area: 192.2 mha (59% of total)

• Area Under Irrigation: 67.2 mha (20% of total)

• Total Irrigation Potential: 139.5 mha (43% of total area)

Distribution of Irrigation Sources in India

This distribution reflects India’s increasing dependency on groundwater sources, with tube wells representing the largest share of irrigation infrastructure.

Classification of Irrigation Projects by Magnitude

Irrigation projects in India are classified based on Culturable Command Area (CCA):

Key Point: Minor irrigation schemes contribute approximately 65% of total irrigation potential utilized across India, despite serving smaller individual areas. Minor irrigation projects utilize both surface and groundwater sources, while Major and Medium projects primarily depend on surface water resources.

Classification Based on Water Distribution Technique

Irrigation systems are categorized into three primary methods of water distribution:

1. Surface Irrigation (Flood Irrigation)

• Water moves under simple gravity influence

• Also known as flood irrigation

• Suitable for level terrain

2. Localized/Micro Irrigation (Low-Flow/Low-Volume Irrigation)

• Water distributed through low-pressure piped networks

• Also known as low-flow or low-volume irrigation

• Includes drip and sprinkler systems

• Higher efficiency and precision application

3. Sub-irrigation (Seepage Irrigation)

• Used in areas with high water tables

• Also known as seepage irrigation

• Water supplied from below ground

Surface Irrigation Methods

Basin Irrigation: Applied to small, leveled areas surrounded by earth banks. Water is applied, allowed to infiltrate, then diverted to adjacent fields.

Furrow Irrigation: Creates small parallel channels along field length. Water flows from one end of the furrow to the other under gravity, suitable for row crops.

Border Strip Irrigation: Field divided into bays or strips. Considered a combination of basin and furrow irrigation. Also called Border Check or Bay Irrigation. Suitable for wheat, leafy vegetables, and fodders.

Localized Irrigation Types

Drip Irrigation (Trickle Irrigation)

• Water delivered at or near root zone, drop by drop

• Includes fertigation capability (fertilizer delivery through drip system)

• Highest efficiency among all methods

• Suitable for orchards and horticulture

Sprinkler Irrigation (Overhead Irrigation)

• High-pressure sprinkles mounted at permanent places

• Challenges: expensive infrastructure, water wastage concerns

Irrigation Based on Water Application Method

Flow Irrigation System: Water conveyed to irrigated land through:

• Direct Irrigation: Water obtained directly from river without storage

• Reservoir/Storage/Tank: Water from river stored through constructed obstruction (e.g., dam)

Lift Irrigation System: Used when water is available at lower levels, lifted by pumps or mechanical devices (example: Indira Gandhi Canal, Rajasthan)

Irrigation Based on Duration of Application

Inundation/Flooding Type Irrigation

• Land allowed to be inundated by water, saturating soil

• Excess water subsequently drained

• Limited to few days of year, uses flood water of rivers

Perennial Irrigation System

• Water supplied according to crop water requirement at regular intervals

• Source can be surface or groundwater

• Provides year-round water availability

Crop-Specific Irrigation Methods

Irrigation Efficiency

Definition: Irrigation efficiency is the ratio between water stored in soil depth inhabited with active plant roots to water applied by the irrigation system.

Key Points:

• 100% irrigation efficiency is practically non-existent due to:

  • Inability to obtain accurate estimates of water needed to recharge root zone

  • Lack of real-time information on actual soil depth of active roots

  • Unavoidable system losses (evaporation, seepage, runoff)

Virtual Water Concept

The concept of “virtual water,” introduced by Prof. Allan in the early 1990s, refers to water required for production of agricultural commodities or water “embedded” in agricultural products.

Water Trade: Exchange of goods implies exchange of virtual water. When a country imports one tonne of wheat instead of producing domestically, it saves approximately 1,300 cubic meters of indigenous water resources.

Introduction

Irrigation is the artificial application of water to agricultural land to supplement natural rainfall and ensure adequate water supply for crop production. With only 2.4% of the world’s landmass and 4% of its water resources, efficient irrigation systems are critical for maximizing agricultural productivity and food security. India’s diverse geography, varying climate patterns, and regional agricultural needs have led to the development of multiple irrigation approaches, ranging from traditional methods to modern technological systems.

Part I: Sources of Irrigation

Irrigation water sources are broadly categorized into surface water sources, groundwater sources, and other supplementary sources.

A. Surface Water Sources

Rivers
Rivers serve as the most common and reliable surface water source for irrigation. Water is diverted from rivers using various structures such as dams, barrages, and canals to irrigate downstream agricultural areas. Major river systems in India like the Ganges, Brahmaputra, Indus, and Godavari have historically been utilized for large-scale irrigation development.

Lakes and Ponds
Natural and man-made lakes provide a secondary source of water, particularly in areas with limited river flow. These water bodies store water during seasons of abundance and serve as reservoirs for irrigation during dry periods. Many regions in central and southern India depend on such systems for agricultural water supply.

Dams and Reservoirs
Dams create large reservoirs that store water during the monsoon season for regulated release during dry periods. These structures provide reliable year-round water availability and serve multiple purposes including irrigation, hydroelectric generation, and flood control. Multipurpose dams combine storage and flood management functions, maintaining water levels close to the design capacity.

B. Groundwater Sources

Wells
Traditional wells are holes dug into the ground to extract subsoil water. These are among the cheapest and most dependable irrigation sources, requiring minimal capital investment. Shallow wells are suitable where the water table is close to the surface, while deep wells serve areas with deeper water availability.

Tube Wells
Tube wells are deeper wells (generally exceeding 15 meters) from which water is lifted mechanically using electric motors or diesel engines. Modern tube wells can irrigate significantly larger areas (approximately 400 hectares) compared to surface wells (half hectare). These are particularly prevalent in northern plains states like Punjab, Haryana, Uttar Pradesh, and parts of Bihar and Gujarat.

C. Other Sources

Rainwater Harvesting
Rainwater harvesting structures capture and store precipitation for later use. This approach is gaining importance in water-scarce regions and complements traditional irrigation systems by reducing dependency on surface and groundwater sources.

Treated Wastewater
In some urban and semi-urban areas, treated wastewater is recycled for irrigation, particularly for non-food crops and horticulture, reducing pressure on freshwater resources.

Desalination
Converting seawater into freshwater through desalination is practiced primarily in coastal areas where saline intrusion affects groundwater quality.

Part II: Types of Irrigation Systems

A. Traditional Irrigation Systems

1. Canal Irrigation

Characteristics and Distribution
Canal irrigation involves diverting water from rivers through man-made canals to irrigate agricultural areas. It is a large-scale irrigation system particularly suited to areas with low relief and fertile soil adjacent to perennial rivers.

• Coverage: Canal irrigation contributes approximately 24% of India’s total irrigated area

• Geographic Distribution: Predominantly concentrated in northern plains, particularly in Punjab, Haryana, Uttar Pradesh, Bihar, and Rajasthan

• Water Application Efficiency: Typically ranges from 30-45%

Advantages

• Provides water throughout the year for perennial crops

• Enables large-scale irrigation of entire regions

• Allows for organized water distribution and management

• Supports command area development with associated infrastructure

Limitations

• High evaporation losses during water transport

• Seepage losses through canal beds

• Significant initial capital investment for canal construction

• Relatively lower water-use efficiency compared to modern methods

• Causes waterlogging and salinization if not properly managed

2. Well and Tube Well Irrigation

Overview
Well and tube well irrigation accounts for 62% of the net irrigated area in India, reflecting its dominant role in Indian agriculture. This system includes traditional dugwells, shallow tubewells, and deep tubewells.

Types of Wells

Dugwells: Traditionally dug shallow wells suitable where the water table is high. These provide water intermittently and are insufficient during dry months.

Shallow Tubewells: Mechanized extraction systems for moderate depths.

Deep Tubewells: Modern deep wells equipped with pumping sets, capable of extracting water from depths exceeding 15 meters. A single tube well can irrigate approximately 400 hectares, making them highly efficient.

Geographic Distribution

• Northern Plains: Uttar Pradesh, Punjab, Haryana, Bihar

• Deltaic Plains: Areas with alluvial deposits near major river deltas

• Peninsular Regions: Particularly in Maharashtra, Gujarat, and parts of Tamil Nadu

Advantages

• Independent source requiring no dependency on external canal systems

• Farmers have direct control over water supply timing and quantity

• Lower capital costs compared to canal projects

• Quick installation and implementation

• Water application efficiency of 60%

Limitations

• Groundwater depletion in over-exploited areas

• Increased pumping costs (electricity/diesel)

• Quality issues in saline groundwater regions

• Uneven development leading to regional disparities

3. Tank Irrigation

Definition and Components
Tank irrigation refers to the storage of rainwater in tanks, ponds, or reservoirs during monsoon season for use during dry periods. The system comprises three essential components:

• Catchment Area: The surrounding land that contributes runoff water

• Storage Tank: The water storage structure with supporting embankments

• Command Area: The irrigated agricultural fields served by the tank

Tank Systems and Structure
Traditional tanks include components such as the main storage body, tank bund (embankment), sluice gates for water management, spillway for overflow, and an intricate network of channels distributing water to fields.

Geographic Distribution and Significance

• Regional Concentration: Predominantly located in southern and central India

• Tank Irrigation Percentage: 3% of total irrigation sources

Advantages

• Suitable for semi-arid and drought-prone regions

• Low operational costs once constructed

• Multi-purpose utility for irrigation, livestock watering, and domestic use

• Supports community-based water management

• Helps regulate seasonal water availability

Limitations

• High sedimentation and maintenance requirements

• Limited capacity for large-scale irrigation

• Subject to evaporation losses during dry season

• Performance dependent on monsoon adequacy

• Requires regular desilting to maintain capacity

4. River Lift Irrigation

Characteristics
River lift irrigation involves mechanically lifting water from rivers and distributing it through canal networks. This system is employed where natural gravity flow is insufficient or where river elevation relative to command area is unfavorable.

Applications

• Used in Punjab and Haryana (from Sutlej River)

• Tamil Nadu (from Cauvery River)

• Andhra Pradesh (from Krishna and Godavari Rivers)

• Telangana (from Godavari River)

• Indira Gandhi Canal (Rajasthan)

Advantages

• Enables irrigation in areas not naturally favored by gravity flow

• Allows utilization of seasonal rivers

• Flexible water supply management

Limitations

• High operational costs due to continuous pumping requirement

• Energy-intensive, increasing agricultural input costs

• Environmental concerns regarding river flow modification

B. Modern Irrigation Systems

Modern irrigation systems employ advanced technology to deliver water more precisely to crops, improving efficiency and reducing water wastage.

1. Sprinkler Irrigation (Overhead Irrigation)

Mechanism and Operation
Sprinkler irrigation distributes water over the crop in the form of spray, mimicking natural rainfall. High-pressure sprinklers are mounted at permanent places, through which water is pressurized and distributed across the field. Water application rates and scheduling can be precisely controlled.

Types of Sprinkler Systems

Stationary Sprinklers: Permanently installed systems suitable for regular cropping patterns.

Mobile/Portable Sprinklers: Can be moved within fields, offering flexibility in managing different crop zones.

Center Pivot Irrigation: A specialized type where a long pipe with sprinklers rotates around a central pivot point, creating circular irrigation patterns. Particularly effective for large uniform fields.

Advantages

• Water application efficiency: 70-85%

• Reduces labor requirements

• Allows for automation and precision control

• Suitable for crops and terrains unsuitable for surface irrigation

• Effective for supplemental irrigation

Limitations

• High initial capital investment

• Expensive initial infrastructure with challenges in water and resource utilization

• Requires regular maintenance of pipes and sprinklers

• Wind drift can reduce application efficiency

• Water pressure dependency

• Energy costs for pressurization

2. Drip Irrigation (Trickle Irrigation)

Definition and Mechanism
Drip irrigation delivers water directly to the plant root zone through a network of tubes, emitters, and valves. Water is released slowly and precisely in small quantities (typically 2-20 liters per hour), minimizing evaporation and runoff.

System Components

• Control station with filters and regulators (including backwash valves, pressure gauges, sand filters, ventury, NRV, bypass valve, screen filter, sand separator, hydro-cyclone, air valve)

• Main supply lines and submain lines with ball valves

• Branch lines and lateral tubes

• Drip emitters

• Flush valves and end stops

• Fertilizer injection capability (fertigation)

Operating Principles
Water is pressurized and directed through the network to individual plant zones, with emitters controlling water discharge. This targeted approach ensures that water reaches only the intended crops, not surrounding areas.

Application Areas in India

• Increasingly adopted across diverse regions

• Particularly suited for horticulture, orchards, and vegetables

• Growing penetration in water-scarce regions

• Suitable for orchards and horticulture

Advantages

• Highest water-use efficiency: 85-95%

• Minimal evaporation and runoff losses

• Reduced weed growth due to targeted wetting

• Uniform water distribution ensuring consistent crop growth

• Lower labor requirements

• Suitable for irregular and sloping topography

• Enables precise nutrient application (fertigation)

• Environmental benefits through reduced chemical runoff

Limitations

• Very high initial capital investment

• Requires technical knowledge for system installation and management

• Vulnerability to clogging by sediment or organic matter

• May not be suitable for all crop types

• Difficulty in scaling for very large farm sizes

• Maintenance-intensive systems

3. Subsurface/Sub-irrigation (Seepage Irrigation)

Mechanism
Subsurface irrigation delivers water directly to the root zone below the soil surface through buried pipes, tubes, or drip lines with emitters placed at regular intervals. Water infiltrates slowly and evenly into the soil. Used in areas with high water tables.

Characteristics

• Water delivered at or below soil surface

• Gradual infiltration matching plant water requirements

• Minimal weed growth due to dry soil surface

Advantages

• Minimal evaporation losses

• Reduced surface weed growth and soil erosion

• Highly efficient water use (80-90%)

• Maintains dry soil surface suitable for equipment movement

Limitations

• Complex installation requiring precise depth control

• Difficulty in system monitoring and maintenance

• Root intrusion into emitters possible

• Higher initial costs

4. Micro-Irrigation Systems

Definition
Micro-irrigation is an umbrella term for low-flow/low-volume irrigation systems including drip and sprinkler methods. These systems are promoted nationally and internationally to achieve higher cropping and irrigation intensities through focused water application.

Characteristics

• Water application directly to crop root zones

• Precise control of water quantity and timing

• Reduced water wastage

• Suitable for diverse topography and soil types

Benefits

• Enhanced water-use efficiency

• Improved crop yields

• Better management of water in water-scarce regions

• Enables cultivation in previously unusable terrain

Part III: Methods of Surface Irrigation

Surface irrigation applies water to the soil surface, allowing infiltration and spreading to irrigate crops. Various surface irrigation methods have evolved to suit different field conditions and crop requirements.

A. Flood Irrigation

Mechanism
Water is released at the upper end of the field and flows gradually across the surface, covering the entire area through gravity flow. Uncontrolled flooding spreads water uniformly, while controlled flooding uses constructed ditches or borders to manage water distribution.

Characteristics

• Simplest irrigation method requiring minimal infrastructure

• Water spreads across field naturally

• Suitable for close-growing crops

Advantages

• Low initial investment

• Simple to implement

• Minimal technical knowledge required

Disadvantages

• Poor water-use efficiency (40-50%)

• High evaporation losses

• Uneven water distribution

• Risk of waterlogging

• Unsuitable for row crops

B. Border Irrigation

Mechanics
The field is divided into strips or borders using low embankments. Water is applied along the borders and allowed to spread laterally across the field. Water runs down the length of the border and infiltrates laterally.

Field Layout

• Rectangular field divisions separated by bunds

• Water supplied from a head ditch along the highest elevation

• Fields typically graded from upper end to lower end

• Open or piped cutlets direct water to borders

Suitability

• Suitable for relatively flat fields

• Effective for uniform crop distribution

• Works well with surface water sources

• Suitable for wheat, leafy vegetables, and fodders

Efficiency

• Water-use efficiency: 60-70%

• Better than simple flooding but lower than modern methods

C. Basin Irrigation

Characteristics
Small depressions or basins are created around individual plants or groups of plants. Water collects and infiltrates around the plant zone, essentially creating submerged or near-submerged growing conditions. Applied to small, leveled areas surrounded by earth banks.

Applications

• Ideal for crops tolerant of standing water (rice, sugarcane)

• Suitable for orchards and tree crops

Mechanism

• Water ponded in basins for fixed duration

• Infiltration occurs over the basin area

• Excess water drains out or is captured

Advantages

• Effective for crops requiring standing water

• Easy to manage water application

• Reduces erosion risk

Limitations

• Suitable only for specific crops

• Requires precise field leveling

• Risk of waterlogging in poorly drained soils

D. Furrow Irrigation

Definition and Method
Small channels or furrows are created between crop rows. Water flows through furrows with infiltration occurring through the wetted perimeter, spreading vertically and horizontally to replenish the soil reservoir. Water flows from one corner of furrow to other under gravity influence.

Design Considerations

• Furrow spacing: Typically 0.4-0.9 meters depending on crop

• Field gradient: 0.1-0.5% depending on soil type

• Sandy soils: Steeper gradients (0.5%) with narrow, short furrows

• Clay soils: Gentler gradients (0.1%) with wide, long furrows

Applications

• Suitable for row crops (maize, cotton, sugarcane, potatoes)

• Effective for annual crops

Advantages

• Water-use efficiency: 60-70%

• Reduces evaporation compared to flooding

• Smaller wetted area reduces evaporation

• Good flexibility in water management

• Topographic variations manageable

Limitations

• Unsuitable for close-growing crops

• Requires skilled management

• Uneven water distribution possible

E. Contour Irrigation

Mechanism
Adapted to sloping terrain, irrigation methods follow the natural contours of the land. Contour bunds (embankments built along contour lines) slow water flow, encouraging infiltration rather than runoff.

Contour Bunds

• Embankments constructed along natural contours

• Height: 50-100 cm; Width: 100-200 cm

• Create micro-catchments intercepting runoff

• Promote deep infiltration

• Reduce soil erosion and gully formation

Benefits

• Soil moisture conservation in dry regions

• Groundwater recharge through infiltration

• Soil erosion control

• Improved crop yields through consistent soil moisture

Part IV: Irrigation Storage Structures and Water Harvesting Systems

Water storage structures capture and retain runoff and surface water for later use, forming the foundation of irrigation systems in many regions.

A. Large-Scale Storage Structures

1. Dams

Dams are engineered structures that obstruct water flow, creating reservoirs for water storage and management. They serve multiple functions including irrigation supply, flood control, hydropower generation, and water supply.

Classification by Function

Storage Dams: Designed to store water during rainy seasons for use in dry periods. The most common type, they maintain water levels close to the designed storage level (USL—Usual Storage Level).

Diversion Dams: Designed to divert water by raising water level without significant storage. Water is diverted into canals for immediate use.

Detention/Flood Control Dams: Specifically constructed for flood mitigation by retarding downstream flow. Water is temporarily retained in reservoirs and gradually released to reduce flood peaks.

Multipurpose Dams: Combine storage and flood control functions simultaneously. Maintain storage sections and control sections, providing both regulated year-round flow and flood attenuation.

Classification by Construction Material

Embankment Dams

• Constructed from earth fill and/or rock fill

• Represent 75% of all dams worldwide

• Built in regions where earth and rock materials are abundantly available

• Rely on compacted fill material without binding agents

Concrete Dams

Gravity Dams: Massive concrete structures resisting water pressure through sheer weight. Depend entirely on structural weight for stability. Require strong bedrock foundations. Today constructed from mass concrete or roller-compacted concrete (RCC).

Arch Dams: Curved upstream structures transferring water force to canyon walls through arch action. Require much less concrete than gravity dams but need solid rock support at abutments. Most suitable for narrow canyons with steep walls.

Buttress Dams: Consist of continuous upstream faces supported by buttress walls on the downstream side. Lighter than solid dams but potentially induce higher foundation stresses. Used in specific geological conditions.

2. Reservoirs

Definition and Types
Reservoirs are open-air storage spaces created by dams or natural formations where water is gathered and stored for multiple uses.

Valley-Dammed Reservoirs: Formed in valleys where mountainsides serve as natural reservoir walls. Dams constructed at the narrowest point provide strength with minimal construction material.

Bank-Side Reservoirs: Constructed beside rivers or streams without valley containment. Require full embankment construction on all sides.

Service Reservoirs: Large clean water storage facilities after treatment in water plants. Often constructed as water towers in flat terrain or underground in hilly areas for distribution to end consumers.

Reservoir Management

• Annual variation in water levels based on inflow and outflow

• Full reservoir level (FRL) represents maximum design capacity

• Dead storage level represents minimum usable water

• Storage capacity typically expressed in million cubic meters (MCM) or acre-feet

3. Anicuts (Weirs)

Definition and Function
Anicuts are low-height barriers constructed across seasonal or perennial rivers to raise water level marginally, facilitating diversion into canals. They differ from dams in their modest height and primary function of water diversion rather than storage.

Characteristics

• Typically 5-15 meters in height

• Quick-opening sluice gates or spillways

• Allows excess water to flow during floods

• Enables immediate water diversion to irrigation channels

Advantages

• Lower cost than full dam projects

• Minimal environmental impact from impoundment

• Flexible operation for varying river flow

Limitations

• Limited storage capacity

• Dependent on river flow availability

• Susceptible to damage during high floods

4. Barrages

Definition and Characteristics
Barrages are structures similar to anicuts but with more sophisticated gate control systems. They comprise multiple radial gates or sector gates that can be opened and closed to manage water levels and flows precisely.

Functions

• Raise water level for canal intake

• Control water release for flood management

• Navigate between irrigation, domestic, and flood management needs

Advantages

• Precise control over water distribution

• Flexible operation during variable flow conditions

• Better flood management than anicuts

B. Medium-Scale Storage Structures

1. Percolation Tanks

Definition and Mechanism
Percolation tanks are artificially constructed earthen embankments designed to facilitate groundwater recharge. They capture surface runoff and store it to allow gradual percolation into aquifers through permeable soil and rock layers.

Location and Site Suitability

• Constructed in areas with permeable soil and fractured rock formations

• Typically located at valley narrowing points that broaden upstream

• Sites must permit adequate percolation

• Maximum storage capacity with minimum investment desired

Design Specifications

• Storage capacity: 2.25 to 5.65 MCM (million cubic meters)

• Suitable for small to medium river courses

• Earthen dams with masonry spillways

• Preferred for second and third-order streams

Functioning Process

1. During monsoon, surface runoff from catchment areas is directed into the tank

2. Water collects and begins seeping through permeable layers

3. Water percolates through soil and rock, reaching groundwater table

4. Stored water gradually releases into groundwater system

5. Zone of influence typically extends 1 km downstream

Efficiency and Performance

• Groundwater recharge efficiency: 78-91%

• Seepage losses: 0-8%

• Evaporation losses: Up to 8%

• Optimal efficiency achieved if tank fills more than once during monsoon

Benefits

• Effective groundwater recharge in hard rock areas

• Natural water filtration during percolation

• Flood mitigation through runoff retention

• Enhanced agricultural productivity through reliable irrigation water

• Environmental benefits maintaining groundwater ecosystems

• Long-term water security

Maintenance Requirements

• Regular desilting to remove accumulated sediment

• Vegetation management on embankments

• Structural inspections and repairs

• Community involvement essential for sustainable operation

2. Check Dams

Definition and Characteristics
Check dams are small barriers constructed across seasonal streams or rivers in command areas to slow water flow, facilitate water infiltration, and reduce soil erosion while promoting groundwater recharge. Constructed in chains to maximize water capture.

Design and Construction

• Constructed across small streams and nullahs

• Crest levels designed so upstream dam’s crest touches downstream dam’s apron level

• Maintains continuous water prism in stream

• Alignment determined by foundation strata viability

• Typically designed to store more than 3 MCM capacity

Multiple Check Dam Systems

• Constructed in chains to maximize water capture

• Sequential filling: upstream tanks filled to 50% capacity first, then release to downstream tanks

• Allows progressive water percolation and infiltration

Advantages

• Cost-effective construction

• Easy maintenance

• Multiple beneficial effects (recharge, erosion control, water availability)

• Suitable for seasonal flow management

Site Requirements

• Minimum 9 inches soil cover required

• Avoid black cotton soils (poor permeability)

• Catchment area and rainfall must be calculated to ensure annual filling

3. Farm Ponds

Purpose and Function
Farm ponds are small excavated structures constructed to store runoff from farm fields in which they are located, providing protective irrigation to the same field during dry periods.

Location and Design

• Positioned at lowest portions of fields where runoff concentrates

• Particularly suitable for rolling slopes

• Excavated to capture surface water

• Sized based on field size and rainfall patterns

Characteristics

• Small-scale storage for individual or group of farms

• Can be open or covered with corrugated iron sheets

• Multi-purpose: irrigation, livestock watering, domestic use

Water Capacity

• Typically serves 0.3 hectares (15 nali)

• Capacity ranges from 1 to 2 lakh liters

• Can provide protective irrigation during critical dry periods

Applications

• Suitable for orchards, vegetable cultivation

• Livestock watering

• Domestic uses in rural areas

4. Low-Density Polyethylene (LDPE) Tanks

Design and Construction
LDPE tanks are specially constructed from low-density polyethylene material in mountainous regions where soil seepage is high. They collect rainwater for irrigation and domestic purposes.

Advantages

• Low cost and simple construction

• Adaptable to earth movements without damage

• Can collect additional water from tank roof

• Not affected by land subsidence

• Minimal maintenance requirements

Applications

• Mountain regions with high seepage potential

• Water-scarce hilly areas

• Orchards and vegetable cultivation

C. Small-Scale and Traditional Water Harvesting Structures

1. Contour Bunds and Field Bunds

Contour Bunds

• Embankments constructed along natural contour lines

• Create micro-catchments intercepting runoff

• Height: 50-100 cm; Width: 100-200 cm

• Spacing varies with terrain slope

• Steeper slopes require closer spacing

Field Bunds

• Low embankments constructed between fields

• Multiple functions: field demarcation and water harvesting

• Support vegetation planting for stability

Benefits

• Soil moisture conservation

• Groundwater recharge

• Soil erosion reduction

• Improved crop yields

2. Excavated Ponds

Characteristics
Simple and cost-effective water storage structures dug in areas with high water tables and impermeable soil capable of holding water.

Advantages

• Low construction and maintenance costs

• Multi-purpose utility

• Easy construction with local labor

Applications

• Irrigation water supply

• Livestock watering

• Fish farming

3. Underground Cisterns

Definition and Use
Cisterns are underground water storage structures commonly used in urban areas to collect and store rainwater harvested from rooftops.

Advantages

• Space-saving (no surface area occupation)

• Temperature regulation (cooler water, reduced evaporation)

Disadvantages

• High initial construction costs (excavation and waterproofing)

• Regular maintenance required for contamination prevention

• Structural integrity concerns

4. Traditional Indian Water Harvesting Systems

Jhalaras (Stepwells)

• Rectangular-shaped structures with tiered steps on three or four sides

• Collect subterranean seepage from upstream reservoirs or lakes

• Designed for religious, ceremonial, and community water supply

• Example: Mahamandir Jhalara in Jodhpur (constructed 1660 AD)

• Aesthetic architectural structures with social functions

Johads

• Small earthen check dams capturing and storing rainwater

• Constructed in areas with natural elevation on three sides

• Excavated storage pit with soil-created wall on fourth side

• Multiple johads interconnected through deep channels

• Regional names: Madakas (Karnataka), Pemghara (Odisha)

• Highly effective in groundwater recharge: 3,000 johads in Alwar district, Rajasthan increased groundwater level by 6 meters; 33% forest cover increase; five rivers became perennial

Baolis (Step Wells)

• Secular structures built by nobility for public water access

• Beautiful architectural features with arches, carved motifs, side rooms

• Locations indicate usage patterns: village baolis for utilitarian and social functions; trade route baolis as resting places

• Agricultural baolis with drainage systems channeling water to fields

• Skilled engineering combining functionality with aesthetics

Phad System

• Integrated irrigation system from West India

• Components: Bhandhara (check dam), Kalvas (canals), Sandams (escape outlets), Charis (distributaries), Sarangs (field channels)

• Operated on Tapi basin rivers: Panjhra, Mosam, and Aram in Dhule and Nasik, Maharashtra

• Sophisticated water management reflecting ancient engineering knowledge

Pat Systems (Maharashtra)

• Traditional irrigation networks using diversion bunds

• Stone piling lined with teak leaves and mud for waterproofing

• Pat channel networks negotiate small nullahs and cliff sections

• Subject to monsoon damage requiring seasonal reconstruction

• Stone aqueducts built to span intervening gaps

Jackwells (Tribal Systems)

• Bamboo-based water collection systems

• Split bamboos placed under trees collecting canopy runoff

• Large jackwells interconnected with smaller wells

• Overflow from upstream well feeds downstream wells

• Adapted water management for forest and tribal regions

Apatani System (Arunachal Pradesh)

• Terraced valley plots divided by 0.6-meter high earthen dams

• Bamboo frame supporting structures

• Individual plot inlets and outlets on opposite sides

• Lower plot outlet functions as higher plot inlet

• Deeper channels connecting inlet to outlet for flood/drain control

• Water tapped from forested hill slopes through 2-4 meter high walls

Part V: Comparative Analysis of Irrigation Methods

Part VI: Geographic Distribution of Irrigation Systems in India

Canal Irrigation: Northern Plains dominance with 24% of total irrigation sources

Well and Tube Well Irrigation: 62% of net irrigated area

• Major States: Uttar Pradesh, Punjab, Haryana, Bihar, Gujarat, Rajasthan, Maharashtra

• Reflects sixfold increase since 1950

Tank Irrigation: 3% of total irrigation sources

• Southern and Central India concentration

• Regional names and applications specific to areas

Micro-irrigation: Growing adoption across diverse regions with special focus on water-scarce regions and horticulture

Part VII: Minor Irrigation Schemes Classification

Minor irrigation schemes contribute approximately 65% of total irrigation potential utilized across India. They are categorized into five major types:

1. Dugwell – Traditionally dug shallow wells

2. Shallow Tubewell – Mechanized shallow extraction systems

3. Deep Tubewell – Deep groundwater extraction systems

4. Surface Flow Schemes – Gravity-fed systems

5. Surface Lift Schemes – Pumping-based systems

Key distinction: Minor irrigation projects utilize both surface and groundwater sources, while Major and Medium projects primarily depend on surface water resources.

Part VIII: Water Application Systems

Direct Irrigation: Irrigation water obtained directly from river without any storage

Reservoir/Storage/Tank: Water from river stored in constructed obstruction (e.g., dam) across river

Lift Irrigation System: Water available at lower levels, lifted by pumps or mechanical devices. Example: Indira Gandhi Canal (Rajasthan)

Key References and Terms

Terms to Remember

• Percolation: Slow seepage of water through soil layers

• Infiltration: Water entry into soil surface

• Runoff: Water flowing over land surface toward streams

• Command Area: Land irrigated by a particular irrigation system

• Catchment Area: Land contributing runoff to a water structure

• Full Reservoir Level (FRL): Maximum designed water storage level

• Water-Use Efficiency: Percentage of applied water used by crops

• Evapotranspiration: Combined water loss through evaporation and plant transpiration

• Waterlogging: Excessive soil water saturation reducing aeration

• Salinization: Accumulation of salts in soil

• Fertigation: Application of fertilizers through irrigation systems

• Virtual Water: Water required for production of agricultural commodities or water “embedded” in agricultural products

Important Statistics

• World’s freshwater resources available to India: 4%

• India’s global landmass proportion: 2.4%

• Total Area: 322 million hectares

• Cropped Area: 192.2 mha (59%)

• Area Under Irrigation: 67.2 mha (20%)

• Total Irrigation Potential: 139.5 mha (43%)

• Well and tube well irrigation percentage: 62% of net irrigated area

• Tube Wells: 46% of irrigation sources

• Canal irrigation: 24% of total irrigation sources

• Tank irrigation: 3% of total irrigation sources

• Other Wells: 16% of irrigation sources

• Other Sources (Springs, Khuls, Dongs): 11%

• Minor irrigation schemes contribution: 65% of total irrigation potential utilized

• Drip irrigation water-use efficiency: 85-95%

• Sprinkler irrigation efficiency: 70-85%

NOTES : AGRICULTURE (UPSC Mains perspective )

ESA: Irrigated areas in India and corresponding land-cover classification map