Managing Water Supplies Study Guide

Global Water Distribution

  • Water distribution:

    • Salt water in oceans: 97.5%

    • Freshwater: 2.5%

    • Surface freshwater: ice sheets, glaciers, lakes, rivers, swamps, marshes, permafrost

    • Sub-surface freshwater: soil moisture, groundwater, permafrost

    • Atmospheric water

Groundwater and Aquifers

  • Groundwater: Water stored underground, filling spaces between soil and rock.

  • Water table: The uppermost level of an aquifer, fluctuates with precipitation and extraction rates.

Types of Aquifers

  1. Confined Aquifer

    • Fully saturated, impermeable layers above and below; artesian wells possible.

    • Clean water, more difficult to remember.

  2. Unconfined Aquifer

    • Recharge from above, permeable layer, fluctuates with seasons.

    • Water is easier to extract, easy to get contaminated.

  3. Perched Aquifer

    • Sits above the water table, close to the surface.

    • Easy to extract, source of natural springs, easily contaminated.

Advantages and Disadvantages

  • Confined: Cleaner water but harder to access.

  • Unconfined: Easier access but vulnerable to surface pollution.

Global Water Demand

  • Sectors:

    • Industrial: Power, manufacturing

    • Municipal: Household usage

    • Agriculture: Livestock and irrigation

Water Security

  • Defined as access to sufficient clean water for food, sanitation, and health.

Causes of Water Insecurity

  • Climate change, droughts, and flooding, changes in rainfall

  • Pollution (surface and groundwater, aresenic contamination)

  • Inadequate sanitation: sewage systems, wastewater management

  • Population growth and urbanization: changes in land usage

  • Competing demands from various sectors

  • Mismanagement of irrigation: water lost through evaporation and moved away from the area

  • Soil salinization: overuse of water in irrigation (high salinity)

Impacts of Water Insecurity

  • Reduced crop yields

  • Livestock mortality

  • Food shortages and malnutrition

  • Illness from contaminated water

Strategies for Managing Water Insecurity

  1. Sustainable Water Extraction

    • Use of pipelines and canals for inter-basin transfers (e.g., Big Thompson Project).

    • Aquifer extraction: Pros: Year-round supply, Cons: Risk of depletion.

  2. Gravity-fed Systems

    • Cold water tank sits up high, a pump hauls water up the roof from the mains supply, and then the tank releases water through outlets in its base.

    • Pros: Cost-effective for small crop areas; Cons: Limited by terrain.

  3. Reservoirs and Dams

    • Pros: Year-round water supply, recreation

    • Cons: Evaporation losses, ecological disruption.

  4. Desalination

    • Distillation and reverse osmosis methods.

    • Pros: Clean water access; Cons: High energy costs, disposal of brine.

  5. Water Usage Reduction

    • Improved irrigation, recycling water, rainwater catchment, education.

  6. International Cooperation: Agreements for sustainable transboundary water resource management.