Water Chapter

Earth's Water Supply

Composition of Earth’s Water

• Oceans provide approximately 97% of the total water supply on Earth, making them the largest reservoir of water.

• Freshwater constitutes only about 3% of the Earth's total water supply; within this small fraction:

  • 70% exists as groundwater, which is stored beneath the Earth's surface in aquifers and is crucial for human consumption and irrigation.

  • 29% is contained as soil moisture, which is largely inaccessible for immediate use but plays a vital role in plant growth and local ecosystems.

  • The remaining 1% is found in lakes, rivers, water vapor in the atmosphere, and living organisms, representing the most readily available sources of freshwater.

Water vs. Diamonds Paradox

• This paradox highlights how water, essential for sustaining life, holds relatively little monetary value compared to diamonds, which, despite their high cost, lack the same utility and necessity for survival. This illustrates how scarcity vs. abundance affects valuation.

Hydrological Cycle

Water Cycle Process

• When water falls on land, it has four primary paths:

  • Transpiration: Movement of water from soil through plants and into the atmosphere.

  • Evaporation: Process where water changes from liquid form to vapor, primarily from oceans, lakes, and rivers.

  • Infiltration: The process by which water soaks into the ground, replenishing groundwater supplies.

  • Runoff: Water that flows over the ground surface towards rivers, lakes, and oceans.

Key Processes Include:

• Evaporation: Facilitated by solar energy, this process is critical in maintaining the Earth's water balance.

• Transpiration: Essential for regulating temperature and cycling nutrients in ecosystems.

• Infiltration: Dependent on soil composition and saturation levels, influencing local water tables.

• Runoff: Can lead to erosion and sediment transportation, impacting ecosystems and human structures.

Water Sources

Categories of Water

• Surface Water: Encompasses all water found on the Earth’s surface, including rivers, lakes, and reservoirs.

• Groundwater: The water stored underground which is now threatened by issues such as salinization and over-extraction, making freshwater increasingly scarce.

• Notably, only about 2% of the total water on Earth is considered freshwater, with even less being both renewable and easily accessible for human use.

Water Withdrawal & Consumption

Definitions

• Withdrawal: Refers to water that is removed from its source for various uses, such as irrigation or municipal supply, and is often returned afterward, albeit not always in the same quality.

• Consumption: Represents water that is not returned back to the source after use, primarily lost through evaporation, incorporation into products, or contamination.

Aquifers

Overview

• Definition: Aquifers are natural underground layers of water-bearing rock or sediment that yield water. They provide about 99% of groundwater that humans utilize for drinking, agriculture, and industry.

• Characteristics:

  • Aquifers may be renewable but are often vulnerable to over-extraction and pollution, necessitating careful management.

  • They do not completely purify water; contaminants can remain, highlighting the need for water treatment.

Groundwater Characteristics

Aquifer Structure

• Comprised of two key zones:

  • Zone of Aeration: The uppermost zone filled with air and water, critical for plant growth.

  • Zone of Saturation: The lower zone that holds groundwater, influencing water table levels.

• Porosity: This refers to the amount of pore space in soil or rock that can hold water, crucial for determining aquifer capacity.

• Permeability: This property describes how interconnected the pore spaces are, affecting the ease with which water can flow through the material.

Overwithdrawal and Diversions

Impacts of Overdraft

• Subsidence: The sinking of land caused by the excessive extraction of groundwater, leading to damage to the infrastructure and increased flood risks.

• Saltwater Intrusion: Occurs when groundwater is depleted faster than natural recharge, causing saltwater to encroach into freshwater aquifers, rendering them unusable.

• Overall, chronic overdraft leads to reduced water quality and diminished supply.

Water Supply Management

Historical Perspective

• The Homesteaders Act of 1862 established foundational land ownership and water rights frameworks, influencing water allocation across 30 states over more than a century. This historical context remains pertinent to contemporary water rights debates.

Water Access Issues

Ownership and Quality Assessment

• Ownership: Water rights are determined by a mix of government and private stakeholders, creating complex management challenges.

• Access and Quality: Critical issues pertaining to economic accessibility for low-income communities and the physical availability of safe water sources must be addressed to promote equity.

Global Water Access Statistics

WHO Estimates

• Individuals need a minimum of 5 gallons per day for basic needs.

• As of 2023, 2.3 billion people lack access to safe drinking water, highlighting stark inequities in water access that vary by geographic and socioeconomic contexts.

Water as a Human Right

United Nations Declaration

• The United Nations recognizes access to safe drinking water and sanitation as fundamental human rights crucial for health, dignity, and well-being.

Definitions of Water Terms

Clarifications by the UN

• Definitions of water quality involve terms such as 'availability,' 'accessibility,' 'treatment,' and 'sanitation,' illustrating the multifaceted nature of global water quality standards.

Measuring Water Stress

Water Stress Indicators

• Water Stress: Defined by the amount of freshwater available per capita; categorized as follows:

  • Below 1700 m³: Stress.

  • Below 1000 m³: Severe Stress.

  • Below 500 m³: Absolute Scarcity.

Global Water Stress

Reported Challenges

• Global water demand is projected to increase by 20-30% by 2050 due to climate change influences, highlighting urgent implications for water resource management.

Climate Change Impacts

Water Resources

• Variable effects from temperature increases could yield either heightened flood risks or increased drought occurrences, dependent on geographical location and regional climate patterns.

Water Pollution Overview

Parametric Definitions

• Potable Water: This is water deemed safe for drinking and recreation, vital for public health.

• Pollutants: Classified into biological (e.g., bacteria), physical (e.g., plastics), or chemical (e.g., heavy metals), each posing potential harm to ecosystems and public health.

Pollution Sources

Categorization

• Point Source Pollution: Identifiable, stationary sources of pollution, such as industrial discharges through smokestacks or drain pipes.

• Non-point Source Pollution: Diffused pollution sources, such as runoff from urban or agricultural land, complicating remediation efforts.

Common Water Pollutants

Types of Pollutants

• Includes variabilities such as soil sediment, harmful chemicals, plastics, raw sewage, and pharmaceuticals, all contributing to the degradation of water quality.

Eutrophication

Causes and Consequences

• Primarily driven by fertilizer runoff, this process leads to harmful algal blooms in water bodies, which deplete oxygen and create 'dead zones' detrimental to marine life.

Cape Fear Water Crisis

Ongoing Issues

• Current public health concerns revolve around PFAS (per- and polyfluoroalkyl substances) contamination linked to industrial processes, raising alarms regarding long-term exposure risks and implications for drinking water safety.

Solutions to the Global Water Crisis

Multi-faceted Approach

• Urgent reconsideration of water as a human right rather than purely an economic commodity is vital, promoting sustainability and equity in water distribution.

• Adoption of community governance models can empower local populations to manage water resources effectively.

Water Governance Framework

Legislative Milestones

• NEPA, EPA, and CWA have established guidelines for regulating water quality and protecting resources; however, these do not fully address emerging contaminants, which remain largely unregulated.

Other Water Initiatives

Charity and Awareness

• NGOs such as CharityWater and Well Aware have been instrumental in raising awareness and improving global access to clean water through innovative community-based projects.

Personal Actions

Encouragement for Individual Responsibility

• Individuals can reduce water waste by adopting conservation practices and exploring innovative methods for water reclamation in their households.

Understanding Virtual Water

Contextual Relevance

• The concept of virtual water emphasizes the water used in the production processes of various goods, particularly in agriculture and textiles, raising awareness of indirect water demand.

Progress and Hope

SDG Report Findings

• Reports indicate advancements in access to safe drinking water and sanitation between 2015 and 2020, suggesting a potential for continued improvements in sustainable water management policies and practices.