Lesson Notes By Weeks and Term v3 - Senior Secondary 1
Under-ground water
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Under-ground water
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Subject: Plumbing And Pipe Fitting
Class: Senior Secondary 1
Term: 2nd Term
Week: 8
Theme: Sources Of Water And Water Treatment
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This topic introduces teachers and learners to underground water as a significant source of water, particularly in the Nigerian context where many communities rely on it for domestic, agricultural, and industrial uses. Understanding the formation, characteristics, and abstraction methods of underground water is fundamental for future plumbers and pipe fitters, as it directly influences water quality assessment, pump selection, pipe material choices, and the design of water supply systems. This knowledge empowers learners to make informed decisions regarding water infrastructure development and maintenance in various Nigerian settings, from rural boreholes to urban water treatment plants.
This section provides a detailed explanation of the core concepts related to underground water, crucial for a comprehensive understanding of the topic. A. Definition of Underground Water Underground water, also known as groundwater, is water located beneath the Earth's surface in soil pore spaces and in the fractures of rock formations. It is a major component of the Earth's freshwater reserves, second only to glaciers and ice caps. Unlike surface water (rivers, lakes), underground water is generally less exposed to direct contamination from human activities, but it can still be affected by pollution seeping from the surface. B. Formation of Underground Water (Hydrological Cycle) Underground water originates primarily from precipitation (rain, snow) that infiltrates the ground.
The process involves:
1. Infiltration: When rain falls, a portion of it seeps into the soil through tiny cracks and pores.
2. Percolation: As the infiltrated water moves downwards through the soil and rock layers due to gravity, this process is called percolation.
3. Saturation: The water continues to move downwards until it reaches an impermeable layer (a layer of rock or clay that water cannot pass through). Above this impermeable layer, the spaces in the soil and rock become completely filled or saturated with water, forming the groundwater body. This saturated zone is where underground water is stored.
C. Key Terminologies Aquifer: This is a geological formation (e.g., sand, gravel, fractured rock) that is porous and permeable enough to store significant quantities of water and transmit it readily to wells and springs. Aquifers are the primary reservoirs of underground water.
Unconfined Aquifer: An aquifer whose upper water surface (water table) is open to the atmosphere through permeable material. It is directly recharged by surface infiltration.
Confined Aquifer: An aquifer overlain by a relatively impermeable layer (aquitard or aquiclude) that restricts the movement of water into or out of the aquifer. Water in a confined aquifer is under pressure and may rise above the top of the aquifer in a well (artesian well).
Water Table: The upper surface of the saturated zone in an unconfined aquifer. It is the level below which the ground is completely saturated with water. The water table fluctuates seasonally and with rainfall patterns; it rises during wet periods and falls during dry periods or due to excessive abstraction.
Porosity: The percentage of void spaces (pores, cracks, fissures) within a rock or soil material. High porosity means a material can hold a large amount of water. For example, sand and gravel have high porosity.
Permeability: The ability of a porous material (like rock or soil) to allow fluids (like water) to pass through it. High permeability means water can flow easily through the material. Sand is highly permeable, while clay has low permeability even though it might have high porosity.
Aquitard/Aquiclude: A layer of rock or sediment that significantly impedes (aquitard) or prevents (aquiclude) the flow of water. Clay is a common aquiclude.
Recharge Zone: An area where water infiltrates the ground and replenishes an aquifer.
Discharge Zone: An area where groundwater emerges to the surface (e.g., springs, rivers, lakes, wetlands). D. Methods of Abstracting Underground Water in Nigeria Given the widespread reliance on groundwater, various methods are employed to bring it to the surface:
1. Hand-dug Wells: These are shallow excavations (typically 5-30 meters deep) dug manually into the ground until they reach the water table. They are common in rural areas and often lined with concrete rings to prevent collapse. Water is usually fetched using buckets and ropes, or by installing hand pumps.
Example: In many villages across the Northern states, families rely on hand-dug wells for daily water needs, especially during the dry season.
2. Boreholes (Drilled Wells): These are deeper, narrower wells created by mechanical drilling rigs. They can reach depths of tens to hundreds of meters, penetrating confined aquifers. Boreholes are lined with casing pipes and equipped with submersible pumps, powered by electricity or generators, to extract water.
Example:* Many urban and peri-urban communities in Nigeria, like parts of Abuja or Port Harcourt, utilize boreholes as a primary source of water supply for individual homes, estates, to leaks and the leaching of heavy metals into the water. pH adjustment (e.g., using soda ash feeders) or non-metallic piping (PVC, PEX) may be required.
Bacterial Contamination: Shallow wells, especially those close to septic tanks or refuse dumps, are susceptible to microbial contamination (E. coli, coliforms). Requires disinfection (chlorination) and proper wellhead protection.
Turbidity: Though generally low, some groundwater can have suspended particles, requiring sedimentation and filtration.
Worked Example/Scenario: A community in Kaduna State plans to install a new borehole system. Initial tests show the underground water has high levels of calcium and magnesium, indicating hard water.
Plumbing Implication: The plumber designing the distribution system must consider this. Galvanized iron pipes, though commonly available, would be highly susceptible to scaling and corrosion over time, reducing flow and lifespan. Copper pipes might also be affected. The recommendation should lean towards uPVC (unplasticized Polyvinyl Chloride) or PEX (cross-linked polyethylene) pipes for the distribution network, which are resistant to scale buildup and corrosion from hard water. Additionally, the plumber should advise the community on the possibility of installing a water softener system if the water is to be used for sensitive appliances or drinking without taste alteration. This demonstrates how understanding groundwater characteristics directly impacts material selection in plumbing. the Northern states, families rely on hand-dug wells for daily water needs, especially during the dry season.
2. Boreholes (Drilled Wells): These are deeper, narrower wells created by mechanical drilling rigs. They can reach depths of tens to hundreds of meters, penetrating confined aquifers. Boreholes are lined with casing pipes and equipped with submersible pumps, powered by electricity or generators, to extract water.
Example: Many urban and peri-urban communities in Nigeria, like parts of Abuja or Port Harcourt, utilize boreholes as a primary source of water supply for individual homes, estates, or even small communities due to erratic public water supply.
3. Springs: These are natural outlets where groundwater flows spontaneously to the Earth's surface. They occur when the water table intersects the land surface, often in hilly or mountainous regions. Springs can be developed by constructing a protective enclosure and a collection chamber to improve water quality and facilitate abstraction.
Example: Some communities in the hilly parts of Plateau State or Cross River State depend on natural springs for their water supply.
4. Artesian Wells: These are wells drilled into a confined aquifer where the pressure is sufficient to force water to the surface without pumping, or to a level significantly above the top of the aquifer. While less common than pump-driven boreholes, they offer a sustainable, low-energy abstraction method.
Example: In certain geological formations, especially in sedimentary basins, artesian conditions can be found, providing self-flowing water sources.
E. Advantages and Disadvantages of Underground Water Advantages: Generally cleaner: Often undergoes natural filtration as it passes through soil and rock layers, making it less susceptible to surface pollutants than surface water.
Constant temperature: Less affected by seasonal temperature changes, making it suitable for various uses without significant pre-heating or cooling.
Reliable supply: Aquifers can store vast quantities of water, providing a more consistent supply, especially during dry seasons when surface water bodies may dry up.
Local availability: Can be sourced relatively close to the point of use, reducing the need for extensive pipe networks.
Less evaporation: Stored underground, it is not subject to evaporation losses like surface water.
Disadvantages: High extraction cost: Drilling boreholes can be expensive due to the depth required and equipment involved.
Deep accessibility: Accessing groundwater often requires deep drilling, leading to higher energy consumption for pumping.
Hardness/Mineral Content: Groundwater can pick up dissolved minerals (e.g., calcium, magnesium) from rocks, leading to hard water which causes scaling in pipes and appliances, and affects soap lathering.
Over-abstraction: Excessive pumping can lead to depletion of aquifers, lowering the water table, causing wells to run dry, and potentially leading to land subsidence.
Difficult to treat pollution: If contaminated, remediation is much more difficult and expensive than for surface water.
Saline Intrusion: In coastal areas (e.g., Lagos, Rivers State), over-abstraction can cause saltwater from the ocean to intrude into freshwater aquifers, rendering them unusable. F. Quality Issues and Plumbing Implications While generally cleaner, groundwater can present specific quality challenges impacting plumbing: Hardness: High mineral content (calcium, magnesium) leads to scale buildup in pipes, water heaters, and appliances. Plumbers must advise on water softeners or select appropriate pipe materials (e.g., PEX, CPVC which are less susceptible to scale than galvanized steel).
Iron/Manganese: High levels cause reddish-brown or black staining on fixtures and laundry, and can lead to pipe clogging. Filtration systems (e.g., iron filters) are necessary.
Sulphur (Hydrogen Sulphide): Imparts a "rotten egg" smell. Requires aeration or specialized filtration.
Low pH (Acidity): Can be corrosive to metal pipes (copper, galvanized steel), leading to leaks and the leaching of heavy metals into the water. pH adjustment (e.g., using soda ash feeders) or non-metallic piping (PVC, PEX) may be required.
Bacterial Contamination: Shallow wells, especially those close to septic tanks or refuse dumps, are susceptible to microbial contamination (E. coli, coliforms). Requires disinfection (chlorination) and proper wellhead protection.
Turbidity: Though generally low, some groundwater can have suspended particles, requiring sedimentation and filtration.
Worked Example/Scenario: A community in Kaduna State plans to install a new borehole system. Initial tests show the underground water has high
A. Teacher Activities: Introduction (10 minutes): Begin by asking students to name sources of water they use daily in their homes or communities. Record responses on the board. Categorize responses into "surface water" and "underground water." Introduce the topic: "Under-ground water" as a critical source, especially in Nigeria. Relate the topic to the hydrological cycle (briefly) to show how groundwater forms. Concept Explanation and Visualisation (25 minutes): Define underground water using clear, simple language. Use diagrams (drawn on the board or projected) to illustrate: The layers of soil/rock, showing the saturated and unsaturated zones. The water table and its position. An aquifer (unconfined and confined). Porosity (using examples like sand vs. clay) and Permeability (how fast water flows through different materials). Explain the formation of groundwater through infiltration and percolation.
Explain key terms: aquifer, water table, porosity, permeability, aquiclude, recharge/discharge zones.
Use local examples: "Imagine digging a well in your village; you'll eventually hit water. That's the water table." Abstraction Methods and Discussion (20 minutes): Describe each method of groundwater abstraction (hand-dug wells, boreholes, springs, artesian wells) using illustrative examples from different parts of Nigeria. Show pictures/videos of these methods if available. Facilitate a class discussion on the prevalence of each method in their local communities and potential challenges (e.g., a well drying up, a borehole pump breaking down). Advantages, Disadvantages, and Quality Issues (20 minutes): Present the advantages and disadvantages of underground water, drawing comparisons with surface water where appropriate. Explain common water quality issues (hardness, iron, acidity, bacterial) that might affect plumbing systems, providing practical implications for plumbers (e.g., pipe material selection, need for treatment). Discuss the worked example from the Key Concepts section regarding hard water and pipe selection in Kaduna. Activity Guidance and Monitoring (10 minutes): Organize students into small groups for a quick activity (e.g., list 3 advantages and 3 disadvantages of boreholes). Monitor group work, provide guidance, and encourage discussion.
Consolidation and Wrap-up (5 minutes): Summarize the main points of the lesson. Address any lingering questions. Assign independent practice.
B. Student Activities: Participate in Discussion: Actively contribute by sharing their experiences with different water sources in their communities.
Note-taking: Copy key definitions and concepts from the board or projected slides.
Visual Interpretation: Observe and interpret diagrams of groundwater systems.
Group Discussion/Activity: In assigned groups, students will discuss and list: Three reasons why a community in their state might choose a borehole over a river as a water source. Two potential problems (plumbing-related) that might arise from using water from a shallow hand-dug well near a refuse dump. (If resources permit, a simple demonstration:* Students can observe a transparent container filled with layers of sand, gravel, and clay, with water poured over to simulate infiltration and water table formation.)
Question and Answer: Ask questions for clarification and answer questions posed by the teacher.
Community Water Supply Projects: In many Nigerian rural and semi-urban communities (e.g., those in Sokoto, Ondo, or Ebonyi states), boreholes and hand-dug wells are the primary sources of potable water. Plumbers are directly involved in the construction, installation of pumps (submersible, hand pumps), and distribution networks from these groundwater sources. Understanding groundwater characteristics (depth to water table, aquifer yield, water quality) is crucial for selecting appropriate pump types, sizing storage tanks, and designing robust distribution systems that serve the community effectively. The knowledge helps in siting wells to avoid contamination and ensures sustainable water abstraction. Managing Water Quality for Domestic and Industrial Use: Many Nigerian households and industries rely on borehole water. Plumbers frequently encounter issues like hard water (calcium/magnesium deposits in pipes/water heaters in Abuja), iron staining (reddish water in parts of Enugu), or acidic water (corrosion of metallic pipes in areas with granite bedrock). Knowledge of groundwater quality allows plumbers to: Advise clients on necessary water treatment systems (e.g., water softeners, iron filters, pH neutralizers). Recommend appropriate piping materials (e.g., uPVC or PEX instead of galvanized steel for hard/acidic water) to prevent premature system failure and ensure longevity. Troubleshoot issues like reduced water flow due to scale buildup or pipe corrosion. Environmental Sustainability and Pollution Prevention: Understanding groundwater helps in promoting responsible water resource management. For instance, in densely populated areas of Lagos or Port Harcourt, improper disposal of domestic and industrial waste can lead to groundwater contamination. Plumbers, by understanding groundwater flow and contamination pathways, can: Advocate for proper sewage disposal and septic tank installation practices to prevent aquifer pollution. Advise on safe distances between wells/boreholes and potential contamination sources (e.g., septic tanks, refuse dumps). Contribute to community awareness on protecting groundwater resources, which is vital for long-term water security.