Week 10 - Water Resources and Water Pollution

Week 10: Water Resources and Water Pollution

1. Earth’s Water Budget

  • Distribution of Water

    • 97% of Earth's water is saltwater; only 3% is freshwater.

    • 2.59% of freshwater is found in ice caps, glaciers, and deep groundwater (difficult to access).

    • Less than 0.5% of freshwater is accessible as soil moisture, surface water in lakes/streams, and groundwater.

  • Importance of Water

    • Essential for life; humans can survive only about a week without it.

    • The human body is approximately 60% water, with critical body components like blood (50%) and brain (77%) made from water.

    • Water impacts various aspects of recreation and weather.

2. Properties of Water

2.1 Chemical Structure

  • Water (H₂O) consists of two hydrogen atoms and one oxygen atom joined by covalent bonding.

  • Molecules bond through hydrogen bonds, creating strong intermolecular forces.

2.2 States of Matter

  • Boiling Point: 100ºC at sea level; decreases with elevation (e.g., 99ºC at 300m).

  • Range of temperature: Water exists as a liquid over a wide temperature range, crucial for life.

  • Unique property of existing in solid (ice), liquid (water), and gaseous (steam) forms at easily achievable temperatures.

2.3 Heat Capacity

  • Specific heat capacity: 4.184 J/gºC (1 calorie needed to raise 1g of water by 1ºC).

  • High heat of vaporization leads to significant energy being required for evaporation, aiding body cooling through perspiration.

2.4 Polarity

  • Water is a universal solvent, dissolving many substances including ionic and polar compounds.

  • This characteristic also makes water more vulnerable to pollution.

2.5 Transparency

  • Water allows light to pass through, essential for aquatic plants to perform photosynthesis.

2.6 Density

  • Ice is less dense than liquid water, allowing it to float, which helps aquatic life survive under ice during winter.

3. The Water Cycle

  • Water cycles through various stages more quickly than other natural cycles and is renewable.

  • Atmospheric moisture renews within 7 days; lakes take about 20 years, while groundwater replenishment may take over a thousand years.

  • Processes in the Water Cycle

    • Evaporation: Water vaporizes from bodies of water and surfaces, including through transpiration from plants.

    • Condensation: Water vapor condenses into clouds, with nimbus clouds producing precipitation.

    • Infiltration: Water enters soil through infiltration, followed by percolation into aquifers.

    • Runoff: Water moves down surfaces back into lakes and rivers.

4. Sources of Water

4.1 Surface Water

  • Water from rivers, lakes, and seas replenished by precipitation and runoff.

  • Critical for freshwater availability, albeit less than groundwater.

4.2 Groundwater

  • Forms through water seeping into soil and permeable rocks, contained in aquifers.

  • Artesian wells and motorized systems are used for extraction, but replenishment is slow, leading to potential depletion.

5. Water Consumption

  • Categorized by domestic (for households), public (for community services), commercial, and industrial uses.

  • Average daily consumption varies widely between communities, with extremes often seen during peak times.

6. El Niño and La Niña

  • These phenomena cause significant variations in weather, leading to drought or excessive rainfall, affecting freshwater availability and agricultural productivity.

  • Conditions Comparison

    • El Niño: Warmer waters, reduced precipitation, dry seasons.

    • La Niña: Colder waters, increased rainfall, and stronger storms.

7. Vulnerability of Water Resources

  • Access to clean water varies significantly; large areas lack sufficient waterworks.

  • Water scarcity can manifest due to natural (drought) and anthropogenic (over-extraction, pollution) causes.

  • Contaminated water poses health risks, needing management to ensure safe drinking supplies.

8. Water Pollution

  • Definition: Degradation of water quality, making it unfit for intended purposes.

  • Historical context: Pre-agricultural societies had minimal impact; population and industrial growth has led to significant pollution.

8.1 Types of Pollutants

  • Heavy Metals: Lead and mercury damage health and disturb ecosystems.

  • Nitrates & Phosphates: Lead to eutrophication, causing algal blooms and reduced oxygen levels.

  • Persistent Organic Pollutants (POP): Long-lasting toxic compounds affecting health and wildlife.

  • Thermal Pollution: Alters water temperatures, disrupting aquatic life.

  • Mine Spills: Release toxic chemicals impacting ecosystems and human health.

9. Water Management Strategies

  • Watershed Protection: Maintain healthy ecosystems, prevent pollution, and ensure sustainable water supplies.

  • Water Treatment Methods: Coagulation, flocculation, sedimentation, filtration, and disinfection to produce safe drinking water.

  • Wastewater Treatment: Essential for sewage management, treating liquid waste for safe discharge or disposal.