Water Demand and Population Growth
- Each person requires water for basic domestic needs such as drinking, cooking, cleaning, and sanitation.
- The World Health Organization (WHO) estimates that each person needs 50-100 liters of water per day for essential domestic use.
- As population increases, total water demand rises proportionally, especially in rapidly growing regions of Africa and South Asia.
- Urbanization exacerbates demand because cities require large-scale supply systems, sewage treatment, and infrastructure expansion.
- The spatial distribution of freshwater is highly uneven.
- While the Amazon Basin holds 20% of global runoff, it supports fewer than 10 million people.
Economic Development and Rising Consumption
- High-income countries (HICs): Use large quantities for domestic comfort — gardening, car washing, pools, and sanitation.
- Middle-income countries (MICs): Show the fastest increase in water demand due to expanding industries and mechanized agriculture.
- Low-income countries (LICs): Depend mainly on agricultural use but face challenges in access and sanitation infrastructure.
The average North American uses around 3 m³ of water per day, compared to 1.4 m³ in Asia and 1.1 m³ in Africa.
Human Use of Water
- Human societies rely on water for domestic, agricultural, industrial, and energy purposes, and as populations grow or economies expand, the demand for freshwater increases dramatically.
- Sustainable management of this resource becomes vital to balance human needs with environmental conservation.
Domestic Water Use
- Domestic water use includes drinking, cooking, washing, cleaning, and sanitation.
- The World Health Organization (WHO) recommends 50–100 liters per person per day to meet basic needs.
- Urban households often consume more water due to piped supplies, washing machines, and gardens, whereas rural communities rely more on manual collection and conservation practices.
- In developing nations, access is often limited.
- Many families spend hours collecting water daily, often from unsafe sources.
- Domestic water use increases rapidly as living standards rise.
- A household in a high-income country may use up to ten times more water per capita than one in a low-income country.
In sub-Saharan Africa, over 300 million people live in areas where water scarcity limits domestic supply, with women and children often spending several hours daily collecting water.
Agricultural Water Use
- Agriculture remains the largest global water user, accounting for about 70% of total withdrawals.
- Irrigation significantly increases crop yields but also drives water depletion.
- Livestock farming uses more water than crop farming due to animal drinking, feed production, and cleaning facilities.
- Modern irrigation systems (sprinkler, drip irrigation) improve efficiency but require investment.
- Always connect agriculture and water security.
- Inefficient irrigation contributes to both scarcity and salinization.
Producing 1 kilogram of beef can require up to 15,000 liters of water, whereas 1 kilogram of wheat requires only around 1,500 liters.
Industrial Water Use
- Industry accounts for about 20% of global water use, though this varies by region.
- Water is used for cooling machinery, cleaning, processing materials, and generating hydroelectric power.
- Heavy industries (steel, chemical, textile) require vast quantities of water, while light manufacturing uses less.
- Industrial water use increases rapidly as economies shift from agriculture to manufacturing.
In Germany, industrial water consumption represents over 50% of total national use, primarily for energy and manufacturing sectors.
Strategies to Meet Growing Water Demands
Increase the Water Supply
- Extracting from new sources: deeper aquifers, rivers, or desalination.
- Building dams and reservoirs to store and regulate water.
- Transferring water between basins (inter-basin transfers).
- Importing water through trade or shared agreements.
Increase the Efficiency of Water Use
- Use low-flow taps and toilets, water-efficient appliances, and greywater recycling in homes.
- Adopt drip or sprinkler irrigation instead of flood irrigation.
- Recycle industrial wastewater.
- Promote education on water conservation.
Improving efficiency may be more sustainable and cost-effective than constantly expanding supply, but both strategies are often needed simultaneously.
Singapore’s “NEWater” project recycles treated wastewater for industrial and potable uses, significantly improving efficiency.
Increasing Water Supplies
- To meet rising demand, societies have developed multiple engineering and ecological methods to increase water availability.
- These include dams and reservoirs, rainwater catchment systems, desalination plants, and wetland enhancement.
- Each strategy has benefits and drawbacks in terms of cost, sustainability, and environmental impact.
1. Dams and Reservoirs
- Dams create reservoirs that store river water for use during dry periods.
- They provide flood control, irrigation water, hydroelectric power, and recreational opportunities.
- However, they can cause displacement of communities, loss of habitats, sedimentation, and altered river flow.
- Evaporation and salinization of stored water are common in hot regions.
The Three Gorges Dam, China, produces hydroelectric power, prevents floods, and supplies freshwater, but displaced over 1 million people and disrupted aquatic ecosystems.
Dams are often controversial because they balance developmental benefits with ethical and ecological costs.
2. Rainwater Catchment Systems
- Collect and store rainfall from rooftops or surfaces in tanks or underground cisterns.
- Useful in both rural and urban settings, particularly where rainfall is seasonal.
- Provide supplementary water for household, agricultural, or industrial use.
- Reduce pressure on municipal systems and can lower water bills.
- Frankfurt Airport (Germany) collects roof rainwater for toilet flushing, air-conditioning systems, and irrigation.
- In India, cities like Chennai and Bengaluru mandate rooftop rainwater harvesting for new buildings.
3. Desalination and Reverse Osmosis
Desalination
Desalination is the process of removing salt and other impurities from seawater to produce freshwater.
- Desalination removes salt and minerals from seawater to produce potable water.
- Two main methods:
- Distillation: Heating seawater and condensing the vapor.
- Reverse Osmosis: Forcing seawater through a semipermeable membrane under pressure.
- Highly effective for arid, coastal regions with energy resources.
- Drawbacks include high energy cost and brine waste, which can harm marine ecosystems.
Desalination works best where energy is cheap but freshwater is scarce—like the Gulf States and Israel.
The Ras Al-Khair Plant, Saudi Arabia uses both distillation and reverse osmosis to supply millions with freshwater and generate electricity from waste heat.
4. Enhancement of Natural Wetlands
- Wetlands act as natural reservoirs, filters, and flood buffers.
- They store water, promote groundwater recharge, and improve water quality by removing sediments and nutrients.
- Restoration of degraded wetlands increases water security and supports biodiversity.
- Protection and enhancement of wetlands are eco-friendly, low-cost alternatives to artificial infrastructure.
- Wetlands function like nature’s kidneys.
- They filter impurities and regulate the water cycle.
South Africa’s Eastern Cape wetlands provide natural water purification and flood regulation while maintaining biodiversity.
How do cultural and economic factors influence the choice of water supply methods in different regions? Consider how these decisions reflect broader societal values.
Environmental and Ethical Considerations
- Large-scale infrastructure (dams, desalination) often raises ethical questions about displacement, cost, and environmental justice.
- A consequentialist view may justify such projects if societal benefits (e.g., energy, water access) outweigh harm.
- A social justice perspective, however, emphasizes equity and the rights of displaced or marginalized groups.
- Describe how dams and reservoirs increase water availability and list two environmental impacts.
- Explain how rainwater harvesting supports both sustainability and conservation.
- Compare the advantages and disadvantages of distillation and reverse osmosis desalination.
- Discuss how wetlands contribute to water quality improvement and flood control.
- Evaluate the ethical issues surrounding large-scale water infrastructure projects like the Three Gorges Dam.
