4.1-4.10: Water and its Management Notes:

Global Water Distribution

• Total water on Earth ≈ 1386 m³.

• 97% saline (oceans).

• 2.5% fresh water:

  • ~68% in glaciers/ice caps.

  • ~30% groundwater.

  • <1% surface water (rivers, lakes, atmosphere, soil moisture, living organisms).

The Water Cycle

• Driven by solar energy, volume of water remains constant.

• Processes:

1. 1. Evaporation (oceans, lakes).

   2. Transpiration (plants).

   3. Condensation → clouds.

   4. Precipitation (rain, snow, dew).

   5. Interception (plants, reservoirs).

   6. Surface run‑off → rivers.

   7. Infiltration/percolation → soil/rocks.

   8. Through‑flow & groundwater flow → aquifers → oceans.

Water Supply

Groundwater

• Stored in aquifers (porous + permeable rock e.g., sandstone, limestone).

• Extracted via artesian wells (sometimes natural pressure).

• Problems: depletion, land subsidence, saline intrusion.

• Examples: Florida aquifer, Bundelkhand (India), Great Artesian Basin (Australia).

Surface Water

• Rivers, lakes, reservoirs (dams).

• Example: Las Vegas relies on Lake Mead (Colorado River).

Desalination

• Removes salt from seawater/brackish water.

• Expensive (≈ US$3/m³).

• Examples: Saudi Arabia (Ra’s Al‑Khair)

Water Usage

• Global use: 9 billion m³/year.

• Average distribution: 70% agriculture, 20% industry, 10% domestic.

• Varies by development level:

  • LEDCs → agriculture dominant (e.g., Zambia: 76% agriculture).

  • MEDCs → industry & domestic dominant (e.g., Belgium: 62% industry, 34% domestic).

Water Quality and Availability

• Global reserves: 42,800 billion m³ → ~5925 m³/person/year (uneven distribution).

• Water‑rich regions: Latin America, North America.

• Water‑poor regions: Middle East, North Africa.

• Types of scarcity:

  • Physical shortage (all reserves exploited).

  • Economic shortage (reserves exist but not exploited due to lack of capital/tech).

• Conflicts: Nile River dispute (Ethiopia’s Renaissance Dam vs Egypt).

• Potable water access:

  • Global: 91% have access.

  • Sub‑Saharan Africa: ~63% access.

  • Rural areas worse than urban.

• Health impacts: 1.5 million deaths/year from diarrhea & water‑borne diseases (mostly children <5).

Multipurpose Dam Projects

• Definition: Large dams storing >3 million m³ water, often serving multiple purposes (irrigation, hydroelectricity, flood control, navigation, domestic/industrial supply).

• Choice of site:

  • Stable geology (hard, impermeable rock like granite).

  • Narrow valley/canyon with deep catchment.

  • Reliable rainfall and tributary streams.

  • Close to demand centers (cities, industries).

  • Availability of local construction materials and worker housing.

  • Avoid high‑value farmland, dense populations, or ecologically/culturally sensitive sites.

• Impacts:

  • Economic: Renewable electricity, irrigation expansion, water security, industrial growth.

  • Social: Displacement (millions worldwide; e.g., Three Gorges Dam displaced >1 million), loss of livelihoods, cultural heritage destruction.

  • Environmental: Habitat flooding, altered river ecosystems, fish migration disruption, eutrophication, methane emissions from reservoirs, disease vectors (mosquitoes, snails).

Water Pollution and Its Sources

• Domestic waste: Sewage, faecal contamination, detergents → diarrhea, typhoid, hepatitis A.

• Industrial processes: Toxic chemicals (lead, mercury), oil spills (e.g., Deepwater Horizon), acid rain from SO₂/NOx emissions.

• Agricultural practices: Fertilizer runoff → eutrophication; pesticides, antibiotics, hormones → bioaccumulation, resistant bacteria; soil erosion → sedimentation.

Impact of Water Pollution

• Global inequalities: MEDCs → advanced treatment; LEDCs → poor sanitation.

• Health risks: Cholera, typhoid, diarrhea; 15 million child deaths annually from contaminated water.

• Industrial toxins: Mercury, arsenic → bioaccumulation in food chains.

• Acid rain: Lowers pH, leaches aluminum, kills aquatic life.

• Eutrophication: Fertilizer runoff → algal blooms → oxygen depletion → ecosystem collapse.

Managing Pollution of Fresh Water

• Improved sanitation: Affordable, sustainable toilets (e.g., Oxfam’s “Fresh Life” project in Nairobi).

• Sewage treatment: Primary (sediment removal), secondary (biological), tertiary (chemical/UV).

• Pollution control & legislation: Environmental permits, fines, EU directives (Urban Waste Water, Bathing Water).

Managing Water‑Related Disease

Malaria

• Life cycle: Parasite (Plasmodium) transmitted by female Anopheles mosquito → human blood → liver → red blood cells → multiplication → mosquito reinfection.

• Control strategies:

  • Antimalarial drugs (prophylaxis, treatment).

  • Vector control: insecticide‑treated nets, indoor spraying, draining stagnant water.

  • Eradication programs (WHO, Gates Foundation goal: eradication by 2040).

Cholera

• Caused by Vibrio cholerae in contaminated water.

• Control strategies:

  • Safe potable water supply.

  • Boiling/chlorination.

  • Improved sanitation.

  • Rapid treatment with oral rehydration salts.

NOTES DONE BY FARIDA SABET

CLICK HERE TO GO TO THE NEXT TOPIC

CLICK HERE TO GO TO THE PREVIOUS TOPIC

CLICK HERE TO GO BACK TO THE NOTES MENU