Study Notes on Water and Water Pollution

Water on Earth

  • Overview of Water and its Distribution

    • Water Cycle

    • Ocean, River, and Ground Water

    • Water Usage

    • Water Distribution and Availability

Renewable Resource

  • Water as a Renewable Resource

    • Water is considered renewable due to the hydrological cycle, where water is constantly recycled.

    • However, the overall volume of water on Earth is limited as there are no new water inflows or outflows in the Earth's system.

    • Concerns: The limited amount of water can lead to issues such as scarcity.

Reservoirs of Water

  • Oceans

    • Cover 70% of Earth’s surface.

    • Contain 97% of the total water supply, equating to 1.4 billion km³ of water.

Understanding Water Distribution

  • Terrestrial Water Storage Components:

    • Lakes

    • Ice Caps and Glaciers

    • Groundwater

    • Rivers

    • Soil Moisture

    • Evapotranspiration

Water Distribution Breakdown by Composition

  • Total Earth Water Volume:

    • Salt Water: 975 mL (97.5%)

    • Fresh Water: 25 mL (2.5%)

    • Surface Water: 2 drops

    • Atmosphere & Soil: 1 drop

Volume and Metric Measurements

  • Volume Measurement Units:

    • Liter (L) is the standard unit.

    • Conversion factors:

    • 1 KL = 1000 L

    • 1 hL = 100 L

    • 1 daL = 10 L

    • 1 dL = 10 mL

    • 1 cL = 100 mL

Water Cycle

  • Processes Involved:

    • Evaporation/Transpiration

    • Condensation

    • Precipitation

    • Runoff

    • Infiltration

Importance of the Water Cycle

  • Water exists in three states:

    • Liquid (Water)

    • Solid (Ice)

    • Gas (Vapor)

  • Energy and Water Exchanges:

    • Solid to liquid, and liquid to gas transitions necessitate energy exchanges.

Energy Exchanges Overview

  • Solid can convert to liquids and gases:

    • Melting, Freezing, Evaporation, and Sublimation.

  • Heat energy is absorbed or released during these phase changes.

Energy and Moisture Content

  • Dew Point:

    • Temperature at which air reaches 100% relative humidity, causing condensation.

Water Vapor Characteristics

  • Easily changes phases with temperature and pressure.

  • Erratic distribution around the world, ranging from virtually absent in some areas to up to 4% atmospheric volume in others.

Role of Sun in Water Cycle

  • Solar Radiation drives evaporation, consuming nearly one-third of the energy reaching Earth's surface.

  • Evapotranspiration:

    • Most evaporation occurs via plants, which can transpire up to 40,000 gallons/year (approximately 150,000 liters).

Water Budget Overview

  • Components of Water Budget:

    • Precipitation (Input)

    • Potential Evapotranspiration (Water demand)

    • Actual Evapotranspiration (Water evaporated)

    • Deficits and Surpluses:

    • Deficit signifies stress for flora and fauna, while surplus refers to excess from rainfall.

Storage Mechanisms in Water Budget

  • Soil Moisture: Stored water in subsurface, accessible by plant roots.

    • Utilization: When demand exceeds supply.

    • Recharge: When supply exceeds demand.

Locations of Fresh Water on Earth

  • 97% of water in oceans, 3% is freshwater.

  • Of the 3%:

    • 70% stored in glaciers and ice caps,

    • 30% ground water, with mere 1.3% in lakes and snow.

Groundwater Dynamics

  • Groundwater moves through aquifers, which are underground layers containing water.

  • Recharge occurs through natural processes or sidewater from rivers.

Human Impact on Groundwater

  • Groundwater is finite; overextraction leads to resource depletion.

  • Often referred to as mining a non-renewable resource.

Surface Water Characteristics

  • Surface water comprises fresh water from precipitation and snowmelt, which integrates into rivers, streams, lakes, and wetlands.

  • Watershed: Area channeling rainfall and groundwater to a common outlet.

Issues with the Hydrological Cycle

  • Excessive groundwater extraction leads to the drying of river streams and degradation of aquatic biodiversity.

Global Water Stress Statistics

  • 1.8 billion people could live in regions with water scarcity by 2025.

  • Global water supply is unevenly distributed and mismanaged.

Access to Safe Water

  • 2.2 billion people live without safely managed drinking water (WHO/UNICEF, 2023).

  • 3.5 billion lack proper sanitation, with millions practicing open defecation.

Water Supply and Sanitation Issues

  • Access and quality are critical factors in safe water usage.

Water Scarcity

  • Defined as either insufficient quantity or lack of access to safe supplies due to population increase and climate change.

Key Drivers of Water Pollution

  • Pollution Sources:

    • Nutrients leading to eutrophication

    • Toxic-chemical pollution (e.g., mercury and lead)

    • Pathogen contamination

    • Point source vs Non-point source.

Effects of Water Pollution

  • Majorly impacts ecosystems and has health repercussions.

Individual Water Use

  • Breakdowns of water use in daily activities, effects on demand and supply.

Solutions and Conservation Strategies

  • Advocate smart water use and conservation practices to manage resources effectively.