lectureslides_mod0601

Module 6.1: Freshwater Resources and Water Wars

Introduction to Freshwater Resources

• Water is vital to life.

• It is a renewable resource recycled through the water cycle.

• Only 2.5% of the Earth's water is freshwater, which is a limited resource.

• Water distribution on Earth is uneven.

• Access and consumption are hindered not only by physical scarcity but also economic scarcity.

• Wise use of water is essential for sustainability.

Case Study: Water Conflicts in the American Southwest

Background

• The Colorado River supplies water to over 40 million people and other organisms.

• In 1922, seven states signed an agreement dividing the river flow based on an overestimated flow.

• Water use has become unsustainable, leading to disputes over water rights.

• Prolonged droughts and climate change escalate this precarious situation.

Future Projections

• The Colorado River often does not reach the Gulf of California, affecting water supply to northern Mexico.

• Lake Mead was only 28% full in 2022, with critical levels affecting dam operations.

  • Below 950 feet: turbines stop functioning.

  • Below 895 feet: water flow ceases.

Distribution and Sources of Freshwater

Freshwater Distribution

• Only 2.5% of Earth’s water is freshwater; many sources are not accessible.

• Freshwater includes surface water (1.2%) and groundwater (30.1%).

  • Lakes/wetlands (23.5%) and glaciers/ice caps (68.7%) also contribute to freshwater sources.

Key Terms

• Groundwater: Water found underground in soil or rock.

• Surface Water: Bodies of water above ground, including rivers, lakes, and oceans.

The Water Cycle

Understanding the Water Cycle

• The water cycle describes the continuous movement of water through various compartments (surface, atmosphere, soil, and organisms).

• Evapotranspiration: combines evaporation and transpiration, where plants release water vapor into the atmosphere.

Water Cycle Process

1. Evaporation: Water heats and rises, cooling to form clouds.

2. Condensation: Water vapor condenses causing precipitation.

3. Runoff: Water moves from higher to lower elevations.

4. Infiltration: Water soaks into the ground and replenishes sources.

Accessing Water Supplies and Associated Problems

Key Concepts

• Surface water can run dry if extraction exceeds replenishment, leading to conflicts (water wars).

• Groundwater depletion from over-withdrawal and decreased infiltration causes wells to dry or become contaminated.

Groundwater Definitions

• Aquifer: Permeable underground soil/rock saturated with water.

• Water Table: The uppermost level of a saturated aquifer.

• Saltwater Intrusion: The inflow of saltwater into freshwater aquifers when freshwater is over-extracted.

Issues from Groundwater Use

• Pollution can affect both surface and groundwater supplies.

• Excessive water extraction creates a cone of depression, dropping water levels dramatically.

Water Use Across Sectors

Sector Breakdown

• Agriculture: 69% of global water use; higher in South Asia.

• Industry: Comprises 19% of total use, varies by economic status of countries.

• Domestic Use: Represents 12% of total freshwater use; increases with income levels.

Agriculture Water Use Highlights

• In the U.S., agriculture accounts for 42% of water use, largely from groundwater (Ogallala aquifer).

• The Colorado River supplies 78% of water to agriculture in its basin states.

Water Scarcity

Definitions

• Water Scarcity: Insufficient access to clean water.

  • Physical Scarcity: Not enough water available.

  • Economic Scarcity: Inability to pay for water access.

Domestic Water Regulation in the U.S.

Key Concept

• The U.S. benefits from a reliable water purification system due to the Safe Drinking Water Act.

• Despite this, violations occur yearly; infrastructure upgrades are necessary.

Safe Drinking Water Act (SDWA)

• Potable Water: Safe for consumption.

• SDWA protects public water supplies.

Flint, Michigan Case Study

• Lead contamination occurred due to improper water source switching; residents suffered severe health issues.

• Low-income communities were most affected; over 100,000 people exposed.

Wastewater Treatment

Definitions

• Wastewater: Contaminated water post-use.

• Wastewater Treatment: Removes contaminants from wastewater.

High-Tech vs. Low-Tech Treatment

• Traditional high-tech methods involve multiple stages (primary, secondary, tertiary treatment).

• Low-tech methods mimic natural ecosystems (e.g., wetlands).

Technologies Addressing Water Scarcity

Dams and Reservoirs

• Dams block river flow; reservoirs store freshwater (e.g., Hoover Dam, Lake Mead).

Desalination

• Removes salt from seawater, mainly in wealthier coastal nations.

Recycling Wastewater

• Important for replenishing water sources (e.g., Las Vegas returns purified wastewater to Lake Mead).

Conservation Practices

Key Concept

• Conservation can mitigate water scarcity through technological advancements, behavioral changes, and consumer practices.

Water Footprint

• Direct Use: Water consumed personally.

  • Average U.S. citizen uses 130 gallons daily.

• Indirect Use: Water used in production of goods; total use can reach 1,100 gallons per person.

Reducing Water Footprint

• Implementing water-saving technologies and adjusting behavior (e.g., shorter showers, full laundry loads) can significantly reduce water consumption.

Summary

• Freshwater is crucial yet limited; access disparities can instigate conflict.

• Technological advancements (dams, desalination) and wastewater treatment are vital to increasing freshwater availability.

• The most effective option is promoting water conservation through technology and behavioral changes.