Week 11, Lecture 3

Freshwater Availability:
- Less than 1% of the Earth's water supply is freshwater.
- Freshwater sources include groundwater, lakes, rivers, and streams.
- Mountain glaciers and snowfields are critical for water supply in many regions.
- Lack of access to safe drinking water is a major global health issue.
- Over 4,000 people die each day due to insufficient access to safe drinking water.

Key Processes in the Hydrologic Cycle:
- Evaporation: Transformation of water from liquid to vapor.
- Transpiration: Release of water vapor from plants.
- Condensation: Transformation of vapor back to liquid, forming clouds.
- Precipitation: Water falls back to the Earth's surface (rain, snow).
- Sublimation: Transition from ice or snow directly to vapor.
- Evapotranspiration: Combined process of evaporation and transpiration.
- Infiltration: Process where water permeates the ground.
- Groundwater Flow: Movement of water through soil and rocks under the ground.
Human Impact on the Water Cycle:
- Activities such as urbanization, deforestation, and industrial processes can affect natural water cycles.

Table 17.2: Volume and Distribution
- Total Water: 1,386,000 km³ (100%)
- Oceans: 1,338,000 km³ (96.5%)
- Ice and Snow: 24,364 km³ (1.76%)
- Saline Groundwater: 12,870 km³ (0.93%)
- Fresh Groundwater: 10,530 km³ (0.76%)
- Fresh Lakes: 91 km³ (0.007%)
- Saline Lakes: 85 km³ (0.006%)
- Soil Moisture: 16.5 km³ (0.001%)
- Atmosphere: 12.9 km³ (0.001%)
- Marshes/Wetlands: 11.5 km³ (0.001%)
- Rivers/Streams: 2.12 km³ (0.0002%)
- Living Organisms: 1.12 km³ (0.0001%)
Average Residence Time:
- Oceans: 2,800 years
- Ice and Snow: 3,000 to 30,000 years
- Saline Groundwater: 1 to 100,000 years
- Fresh Groundwater: days to thousands of years
- Lakes: days to thousands of years
- Soil Moisture: 1 to 500 years
- Atmosphere: 2 weeks to 1 year
- Marshes: Months to years
- Rivers: 1 week to 1 month
- Living Organisms: 1 week

River Formation:
- Rivers collect water that does not infiltrate the ground and flow to the ocean due to gravitational pull.
Discharge:
- Definition: A measure of the size or flow rate of a river.

Hydrology Zones:
- Zone of Aeration: Area where soil and rock are not saturated with water.
- Zone of Saturation: Area where soil and rock are fully saturated with water, containing groundwater resources.
Components:
- Well: Man-made structure to access underground water.
- Spring: Natural discharge of groundwater at the surface.
- Water Table: The upper surface of the zone of saturation.
- Aquifers:
- Definition: Porous layers of sand, gravel, or rock that serve as reservoirs for groundwater.
- Types:
  - Unconfined Aquifers: Surrounded by permeable materials.
  - Confined Aquifers: Bounded above and below by impermeable rock layers.

Importance of Wetlands:
- Slow surface runoff, allowing water to replenish aquifers.
- Historically, 20% of the U.S. was wetland; loss leads to increased flooding and erosion.

Non-renewable Resource:
- Many aquifers do not recharge at a sustainable rate due to high consumption.
Case Study: Ogallala Aquifer in the Great Plains
Saltwater Intrusion: Problem arising when excessive groundwater extraction leads to the encroachment of saltwater into freshwater aquifers.
Land Subsidence:
- An example of land sinking in places such as the San Joaquin Valley (1926-1970 range).

Sources:
- Primary source: Susquehanna River
- Backup source: Small groundwater supply.

Global Variability:
- Freshwater is available but not evenly distributed and often polluted.

Statistics:
- Share of Population with Access:
- 85% or more, 70-85%, 55-70%, 40-55%, less than 40%, no data.
Freshwater Availability:
- Measured in cubic meters per person per year for 2007, showing high levels of scarcity in certain regions.

Hotspots:
- Regions experiencing volatile water conditions, especially in the western U.S., affecting agriculture and urban growth.
Major River Systems Under Stress:
- Includes Nile, Jordan, Yangtze, and Ganges.
Future Projections:
- Over 30 countries facing scarcity; estimated 60 countries by 2050.
- 30% of the Earth’s land area predicted to experience severe drought, worsening over time.

Lake Mead:
- Created by Hoover Dam in 1985, has seen a significant drop in water levels from 1,225 ft in 1983 to 1,061 ft in 2024.
Water Shortage:
- Tier 1 Water Shortage declared for the Colorado River in 2025.

Rainfall Comparison:
- Phoenix: 8.2 inches annually vs. Chicago: 36.9 inches.
- Inconsistent drought conditions for the past 20 years; discourse on water supply management and politics.
Suggestions for Solutions:
- Proposal of a pipeline from the Great Lakes to Arizona.

Major Contributor:
- Agriculture accelerates water scarcity.
Case Study: Riverview LLP, a large dairy farm with a heavy reliance on groundwater and extensive well drilling affecting local water supply.

Utah’s Environmental Issues:
- Discussion points from a podcast focusing on health and environmental consequences of drying lakes.

Worldwide Water Use Data (km³/year):
- Agricultural sector as the predominant user of water, tracking global water withdrawals over the past century.
Water Requirement for Production:
- Liters of water required to produce 1 kg of various agricultural products (e.g., corn, potatoes, soy, etc.).

Definition:
- Also known as virtual water or embodied water; refers to the total amount of water used throughout a product's production process, even if the final product is not water-derived.

Consumer Level:
- Installation of low-flow devices, adopting plant-based diets, reducing clothing purchases.
Government Level:
- Implementation of water regulations, upgrading wastewater treatment, and advancements in desalination technology.

Methods:
- Distillation and reverse osmosis techniques utilized.
Energy Efficiency:
- Potential energy reductions by coupling desalination facilities with power plants.
Environmental Consideration:
- Management of brine waste generated from desalination processes.

Recycled Water:
- Process flow for utility delivering safe drinking water after wastewater treatment.
- Involves trash, chemical, and contaminant removal at wastewater treatment plants followed by drinking water purification.