Module 2: Ground water

Groundwater: Definition, Types, Importance, and Challenges

1. Definition of Groundwater

Groundwater is the water that exists beneath the Earth's surface in the
pores of rocks, soils, and sediments. It is a crucial part of the hydrological
cycle and accumulates in underground reservoirs known as aquifers.
Groundwater moves through these porous layers via the process of
infiltration and percolation, eventually supplying water to wells,
springs, and surface water bodies.

2. Aquifer: Definition, Types, Importance, and Management

1. Definition of Aquifer

An aquifer is a body of permeable rock or sediment that stores and

transmits water. Aquifers can vary in size and depth, and they are
essential components of the Earth's hydrological system. Water in
aquifers is referred to as groundwater and can be accessed through
wells, springs, or natural outflows to surface water bodies like rivers and
lakes.
2. Types of Aquifers

Aquifers are categorized based on their location, structure, and the way
they interact with surrounding materials. The two main types are:

A. Unconfined Aquifer

 Definition: Also known as a phreatic aquifer, an unconfined

aquifer is one where the water table is open to the atmosphere and
is not confined by any impermeable layer above it.
 Characteristics:
o The water is directly recharged by rain or surface water.
o Easily accessible, but more vulnerable to contamination from
surface pollutants.
o Water levels fluctuate based on rainfall and extraction rates.
 Example: Shallow aquifers found in river valleys or floodplains.

B. Confined Aquifer

 Definition: A confined aquifer, also known as an artesian aquifer,

is trapped between two impermeable layers of rock or clay.
 Characteristics:
o Water in a confined aquifer is under pressure, which can
cause it to flow to the surface naturally when tapped (artesian
wells).
o Less vulnerable to contamination but harder to recharge
because it is isolated from the surface environment.
o Water in confined aquifers tends to be older and more
mineralized.
 Example: Deep aquifers beneath large geological formations.

3. Importance of Groundwater

Groundwater plays a vital role in various aspects of life:

A. Drinking Water Supply

 Groundwater is a primary source of drinking water for millions of

people, especially in areas where surface water is scarce or
contaminated.

B. Irrigation

 It is essential for agricultural activities, especially in regions with

irregular rainfall patterns. Groundwater is a key irrigation source,
particularly during dry spells.

C. Industrial Use

 Industries such as manufacturing, food processing, and mining rely

on groundwater for operations, cooling, and processing purposes.

D. Ecosystem Support

 Groundwater contributes to the base flow of rivers, lakes, and

wetlands, supporting aquatic ecosystems, particularly during dry
seasons.

E. Water Storage

 Groundwater acts as a natural storage system, providing water

during times of drought or low rainfall, helping to balance seasonal
water availability.

4. Challenges to Groundwater

Despite its importance, groundwater faces several challenges, particularly

due to human activities and natural factors:

A. Over-extraction
  Excessive extraction for agricultural, industrial, and domestic use
can lead to a significant drop in groundwater levels, especially in
areas with high water demand.
 Consequences: Groundwater depletion, land subsidence (sinking of
the ground), and reduced water availability for future use.

B. Groundwater Pollution

 Agricultural Runoff: Chemicals such as pesticides, fertilizers, and

herbicides leach into the ground and contaminate groundwater.
 Industrial Discharge: Toxic chemicals, heavy metals, and waste
from factories can pollute aquifers, making the water unsafe for
consumption.
 Sewage and Wastewater: Inadequate sanitation infrastructure
leads to contamination by bacteria, viruses, and chemicals.
 Saltwater Intrusion: In coastal areas, over-extraction can cause
the intrusion of seawater into freshwater aquifers, making the water
saline.

C. Climate Change

 Changes in precipitation patterns, rising temperatures, and more

frequent droughts can impact the replenishment of groundwater
reserves, exacerbating water scarcity issues.

D. Uneven Distribution and Accessibility

 Groundwater resources are not evenly distributed across the globe.

Some regions experience high water table levels, while others suffer
from deep aquifers, making it costly and difficult to access.
 Equity Issues: Poorer regions with fewer resources may struggle to
access safe and clean groundwater.

E. Lack of Groundwater Management

  Unregulated extraction, poor monitoring, and insufficient awareness
of groundwater conservation lead to inefficient use and
unsustainable depletion.

Water quality is a critical factor that directly impacts human health

and well-being. Contaminated water can lead to a wide range of
health problems, from mild illnesses to life-threatening diseases.

Types of Water Contaminants:

Microbial Contaminants: These include bacteria, viruses, and protozoa

that can cause waterborne diseases like cholera, typhoid, dysentery, and
diarrhea.
Chemical Contaminants: These can be inorganic substances like heavy
metals (lead, arsenic, mercury), nitrates, and fluorides, or organic
compounds like pesticides, industrial chemicals, and pharmaceuticals.
Chemical contamination can lead to various health issues, including
poisoning, organ damage, and cancer.
Physical Contaminants: These include sediment, debris, and other
particles that can make water cloudy and affect its taste and odor. While
not always directly harmful, physical contaminants can make water less
appealing to drink and may harbor harmful microorganisms.
Radiological Contaminants: These are radioactive substances that can
occur naturally or result from human activities. Exposure to radioactive
contaminants can increase the risk of cancer and other health problems.

Health Impacts of Contaminated Water:

 Waterborne Diseases: These are infections caused by pathogens

in contaminated water. They can cause diarrhea, vomiting, fever,
and in severe cases, can be fatal, especially for children and people
with weakened immune systems.
 Chronic Diseases: Long-term exposure to chemical contaminants
in water can lead to chronic health problems like cancer, kidney and
 liver damage, neurological disorders, and developmental problems
in children.
 Malnutrition: Contaminated water can cause diarrhea and other
gastrointestinal illnesses, which can interfere with nutrient
absorption and lead to malnutrition.
 Skin Diseases: Contact with contaminated water can cause skin
rashes, infections, and other skin problems.

Dental Problems: High levels of fluoride in drinking water can cause

dental fluorosis, a condition that affects the development of teeth.
Vulnerable Populations:
Children: Children are more susceptible to waterborne diseases and the
effects of chemical contaminants due to their developing immune systems
and smaller body size.
Elderly: Older adults may have weakened immune systems and pre-
existing health conditions that make them more vulnerable to the effects
of contaminated water.
People with Weakened Immune Systems: Individuals with HIV/AIDS,
cancer, or other conditions that compromise their immune systems are at
increased risk of waterborne diseases.
Pregnant Women: Pregnant women are more susceptible to infections,
and contaminated water can pose risks to both the mother and the
developing fetus.

Ensuring Safe Water:

 Water Treatment: Proper treatment of water, including filtration

and disinfection, can remove most contaminants and make it safe
for drinking.
 Water Quality Monitoring: Regular monitoring of water sources
and treated water is essential to ensure that it meets safety
standards.
 Sanitation: Proper sanitation practices, including safe disposal of
sewage, are crucial for preventing water contamination.
  Public Awareness: Educating the public about the importance of
safe water and how to prevent waterborne diseases is essential.

Definition of Water Harvesting

Water harvesting refers to the process of collecting and storing

rainwater or runoff from various surfaces, such as rooftops, pavements,
and land, for later use. It is a sustainable solution to conserve water,
recharge groundwater, and address water scarcity, especially in regions
facing irregular rainfall or drought conditions.

Methods of Water Harvesting

A. Rooftop Rainwater Harvesting

 Method: Water is collected from rooftops and directed into storage

tanks through a network of gutters and pipes. The collected water is
typically filtered before use.
 Applications: Domestic use, irrigation, and sometimes for
groundwater recharge.
 Best for: Urban areas, households, and institutions with suitable
rooftop spaces.

B. Surface Runoff Harvesting

 Method: This involves collecting rainwater runoff from roads, fields,

or large surfaces. The water is usually stored in ponds, tanks, or
artificial reservoirs.
 Applications: Agricultural irrigation, groundwater recharge, and
flood control.
 Best for: Rural areas, agricultural fields, and larger surface areas.

C. Check Dams and Small Reservoirs

  Method: Small dams or embankments are built across streams or
small rivers to capture water during the rainy season. These
structures help to retain and store water for later use.
 Applications: Agriculture, domestic water supply, and ecosystem
maintenance.
 Best for: Areas with small rivers or seasonal water flow.

D. Percolation Pits

 Method: Pits or trenches are dug to capture rainwater and allow it

to percolate into the ground to recharge the groundwater table.
 Applications: Groundwater recharge, preventing surface runoff,
and enhancing soil moisture.
 Best for: Rural areas, agricultural lands, and regions with shallow
aquifers.

E. Ponds and Lakes

 Method: Constructing ponds or small lakes to collect surface runoff

from nearby areas during the rainy season.
 Applications: Irrigation, livestock watering, and ecosystem
support.
 Best for: Rural areas, agricultural lands, and larger land holdings.

F. Permeable Pavement

 Method: Installation of permeable materials (such as gravel, porous

concrete, or asphalt) on roads or pavements that allow water to
infiltrate and be captured beneath the surface.
 Applications: Urban water management, preventing flooding, and
groundwater recharge.
 Best for: Urban areas and places with high impervious surfaces.

Classes of Water Harvesting Systems

Water harvesting systems can be categorized based on their scale and the
method of collection:

A. Domestic Water Harvesting

 Focus: Primarily involves the collection of water from roofs or small

catchment areas for household use.
 Features: Small-scale storage tanks, simple filtration systems, and
easy installation.
 Example: A rainwater harvesting system installed on a house or
apartment complex.

B. Agricultural Water Harvesting

 Focus: Larger-scale systems to collect water for irrigation, livestock,

or groundwater recharge.
 Features: Can include check dams, ponds, percolation pits, and
rainwater collection from agricultural fields.
 Example: A farm using check dams to collect water for irrigation
during the dry season.

C. Community Water Harvesting

 Focus: Large-scale harvesting for public use, such as supplying

water to villages or small towns.
 Features: Large storage tanks, ponds, or wells that serve the local
population or multiple households.
 Example: A village-wide water harvesting system to provide water
for drinking, irrigation, and sanitation.

D. Urban Water Harvesting

 Focus: Capturing rainwater in urban areas to manage storm water

runoff and provide an alternative water source.
 Features: Rainwater collection from roofs, permeable pavements,
and storage in tanks or reservoirs.
  Example: An apartment complex or commercial building using
rooftop harvesting systems.

Benefits of Water Harvesting

A. Water Conservation

 Water harvesting helps reduce dependency on conventional water

sources like rivers, lakes, and groundwater, conserving these
resources for future use.

B. Groundwater Recharge

 By allowing rainwater to percolate into the ground, water harvesting

replenishes groundwater levels, which is especially crucial in
areas facing groundwater depletion.

C. Flood Control

 Capturing rainwater during the rainy season reduces surface runoff,

preventing flooding in urban areas or low-lying regions.

D. Agriculture Support

 Water harvesting systems ensure that water is available for

irrigation during dry spells or droughts, improving agricultural
productivity and food security.

E. Cost Savings

 Using harvested rainwater reduces reliance on municipal water

supplies, leading to significant cost savings on water bills for
households and businesses.

F. Environmental Benefits
  By preventing surface runoff, water harvesting reduces soil
erosion, enhances soil moisture, and protects local ecosystems.
 It also helps reduce storm water pollution by capturing water
before it can carry pollutants into water bodies.

G. Resilience to Climate Change

 Water harvesting can enhance resilience to changing rainfall

patterns, droughts, and water scarcity, particularly in areas
vulnerable to climate change.

H. Improved Water Quality

 Collected rainwater is often cleaner than surface water because it

is not exposed to contaminants like industrial waste or agricultural
runoff.

Subsurface Barriers/Dykes

A subsurface barrier or dyke is an underground structure designed to

control the movement of groundwater. These barriers are typically made
from impermeable materials like clay, concrete, or geomembranes. They
are constructed below the surface to prevent water from flowing in or out
of certain areas, usually to create or protect water storage or irrigation
systems.

Types of Subsurface Barriers/Dykes

 Impermeable Barriers: These barriers are designed to prevent

water from infiltrating or flowing through them. They are made of
materials such as clay, cement, or synthetic membranes that have
very low permeability.
 Permeable Barriers: In some cases, permeable materials are used
in barriers to allow controlled groundwater flow, especially for water
conservation or recharge purposes.
Applications in Rural Areas

 Flood Control and Protection: Dykes are often constructed along

riverbanks or agricultural fields to control the flow of surface water,
preventing flooding and waterlogging, which can damage crops and
land in rural areas.
 Groundwater Flow Management: Subsurface barriers are used to
direct or block the movement of groundwater in areas with
excessive infiltration or where groundwater recharge needs to be
controlled. This is particularly important for maintaining the balance
of local aquifers.
 Water Storage and Irrigation: In some cases, subsurface dykes
are used to create localized water reservoirs by stopping water from
flowing out of certain areas. This helps in storing rainwater or
floodwater, which can later be used for agricultural irrigation or
other purposes.

Benefits of Subsurface Barriers/Dykes in Rural Areas

 Flood Mitigation: They help in preventing surface water from

flooding farmland or villages, especially during heavy rains or
seasonal floods.
 Soil and Crop Protection: By preventing waterlogging, subsurface
barriers protect crops from being submerged or suffering from
excess moisture, ensuring better yields.
 Groundwater Recharge Management: They help manage
groundwater recharge, ensuring that only the necessary amount of
water seeps into aquifers, preventing over-extraction or salinization.

Challenges

 High Cost: Construction of subsurface barriers can be expensive,

especially in large areas, and may require specialized materials and
expertise.
  Maintenance: Over time, subsurface barriers may require
maintenance to ensure they continue functioning effectively,
especially in areas with fluctuating water levels.

2. Ponding

Definition: Ponding refers to the practice of collecting and storing

rainwater or runoff in natural or artificial depressions (ponds) for
agricultural, domestic, or environmental use. Ponding is an essential
practice in water management, particularly in rural areas, where water
storage is crucial for irrigation and livestock.

Applications of Ponding in Rural Areas

 Irrigation: Ponds store rainwater that can be used to irrigate crops

during dry spells or droughts. This ensures that agriculture is
maintained even in times of insufficient rainfall.
 Livestock Watering: Ponds also serve as a reliable water source
for livestock, especially in rural areas where access to centralized
water supplies may be limited.
 Flood Control: In flood-prone areas, ponds can help capture and
store excess rainwater, reducing surface runoff and preventing soil
erosion. This helps mitigate flooding in fields or villages.
 Aquaculture: Ponds can be used for fish farming, providing an
additional source of livelihood for rural communities.

Benefits of Ponding in Rural Areas

 Water Storage: Ponds provide an easy and low-cost method of

storing water during the rainy season, which can be utilized during
periods of water scarcity.
 Improved Crop Production: By providing a consistent water
supply, ponds support crop production, especially in rain-fed areas
where irrigation infrastructure is inadequate or absent.
  Soil Erosion Control: Ponds help slow down the speed of runoff,
reducing soil erosion and helping maintain the fertility of agricultural
land.
 Biodiversity Support: Ponds create habitats for various aquatic
plants and animals, enhancing local biodiversity.

Challenges of Ponding

 Evaporation Losses: In hot and dry climates, water stored in

ponds may experience high evaporation losses, reducing the
amount of usable water.
 Water Quality Issues: Without proper management, ponds can
become breeding grounds for mosquitoes or accumulate pollutants,
making the water unsuitable for agricultural or domestic use.
 Maintenance: Ponds require regular maintenance to ensure they
remain free of debris, sediment build-up, and algae, which can
affect water quality and storage capacity.

3. Combining Subsurface Barriers and Ponding for Water

Conservation

In rural areas, combining subsurface barriers with ponding techniques can

enhance water management practices:

 Integrated Systems: Subsurface barriers can be used to prevent

water from draining away from ponds or agricultural fields, ensuring
that water stored in ponds can infiltrate the soil and recharge
groundwater. This synergy improves overall water availability.
 Enhanced Water Storage and Utilization: Ponding allows surface
storage, while subsurface barriers can ensure that water does not
escape and helps in maintaining the required groundwater levels. This
combined approach is particularly beneficial in dry regions, where
surface water can be scarce during certain times of the year.