Dynamic Earth GY4741: Water Resources - Use

Dynamic Earth GY4741: Water Resources - Use

Lecture Outline

  • 1. Water resource issues
  • 2. Human modification of water systems
  • 3. Water abstraction

The Water Resource

Natural Resource
  • Fundamental: Water is essential for all life forms on Earth.
  • Uneven: Water distribution is not uniform across geographical areas.
  • Renewable Globally: Although water is continually cycled through natural processes, the availability is not the same everywhere.
  • Finite Locally: Specific local sources can be limited.
  • Supports All Life: All terrestrial life forms rely on water.
  • Transport Medium: Water acts as a medium for transporting nutrients and energy.
  • Habitat: Species live in and depend on water habitats.
  • Nutrient Recycling: It plays a vital role in cycles such as the nutrient cycle.
  • Hydrological Cycle: Purifies water through processes like evaporation and condensation.
Human Resource
  • Abstraction: Extraction of water from its natural environment.
  • Consumption: Water used for different purposes.
  • Grow Food: Agriculture relies on water for irrigation.
  • Irrigation: Application of water to agricultural land.
  • Waste Disposal: Water is used for diluting and transporting waste.
  • Recreation: Water bodies provide recreational activities.
  • Water Transport: Waterways serve as transport routes.
  • Hydroenergy (Electricity): Water is a primary source of renewable energy through hydropower.
  • Industry: Used for processes, including cooling.
Ecosystem Services
  1. Provisioning: Supply of water and food.
  2. Supporting: Services essential for the production of other ecosystem services, like habitat provision.
  3. Regulating: Maintaining ecosystem processes.
  4. Cultural: Benefits that water bodies provide to society, including recreational and aesthetic values.
  5. Reference: UNEP Millennium Assessment, 2005.

Water Resource Issues

Factors Affecting Water Resource Management
  • Time: Rainfall does not occur where most needed, making water storage crucial.
  • Space: Many water sources are distant from areas of high demand, necessitating storage and transfer solutions.
  • Quality: Water often requires treatment to be fit for human consumption.
  • Renewable vs. Finite: Water can be a renewable resource globally but is finite locally.
  • Distribution Issues: Uneven distribution manifests on geographical scales, affecting demand and supply dynamics.
  • Developed vs. Developing World: Disparities in access and management of water resources are significant between developed and developing countries.
High and Low Water Issues
Too Much Water
  • Causes:
    • High Precipitation: Leads to flooding.
    • High Run-off Rates: Can overwhelm local drainage capacities.
    • Limited Channel Capacity: Both natural and human modifications can restrict water flow.
Too Little Water
  • Causes:
    • Low Precipitation and High Evaporation: Atmospheric conditions contribute to drought.
    • Meteorological Drought: Extended periods of dryness can severely limit water availability for agriculture and drinking.
    • Hydrological Supply: Reduced water bodies affect availability.
    • Socioeconomic Factors: Demand exceeds supply, leading to conflicts.
Factors Influencing Water Issues
  • Permanent Factors:
    • Slope: Affects drainage and water flow patterns.
    • River Network: Complexity of a river system can influence water management strategies.
  • Transient Factors:
    • Storms: Can lead to sudden influxes or deficiencies in water supply.
    • Infiltration: Water absorption into the soil can affect surface availability.

Water – A Human Resource

Historical Context
  • Ancient Hydraulic Civilisations: These societies utilized water management for agricultural productivity and flood control.
  • Productivity: Effective irrigation systems increased food yields.
  • Protective Roles: Water management also played a significant role in flood mitigation.
  • Rain-fed Agriculture: Agriculture often confined to areas with abundant water resources.
Water Resource Management Techniques
  1. Irrigation: Essential for effective agricultural practices.
  2. Drainage: Management of excess water to safeguard crops.
  3. Impoundment: Use of dams to store water.
  4. Transfer: Moving water from one location to another to meet demand.
  5. Regulation & Diversion: Altering natural water flow for varying uses.
  6. Groundwater Exploitation: Over-extraction can lead to depletion and quality issues.
  7. Case Study: Petra, Jordan - historical irrigation analysis.
  8. Water Supply Enhancement: Only approximately 1% of the Earth's water is potentially available for human use.
Dams and Environmental Impacts
  • Long History of Dams: Significant for water regulation and supply.
  • Water Mills: Traditional methods of water utilization.
  • Hydroelectric Power: An important renewable energy source enabled by dam technology.
  • Environmental Impacts from Dams:
    • Landscape Changes: Dams alter natural landscapes and waterways.
    • Flow Disruption: Changes can affect downstream water availability and quality.
    • Sediment Trapping: Dams trap sediments which reduces nutrient supply downstream and increases water's erosive power.
Geopolitics & Water Use
  • Access Issues: Water resource access can vary significantly by region, often aligning with political boundaries.
  • Conflict: Water can be leveraged as a weapon during disputes, raising concerns about equitable access and distribution.
  • Example: The Atatürk Dam on the Euphrates River highlights water access issues among Turkey, Syria, and Iraq totaling up to 90% of flow regulation in Turkey.

Case Study: Colorado River System

  • Lake Mead's Issues: Water levels have dropped to 64% of capacity due to excessive use exceeding supply.

Structural and Functional Changes in Water Management

Physical Alteration of Drainage Patterns
  1. Arterial and Field Drainage: Alteration of natural drainage patterns can lead to flooding if not managed properly.
  2. Embankments: Levees can protect certain areas but may disrupt natural water systems.
  3. Channel Realignment: Straightening and deepening rivers to control floods.
  4. Dredging and Clearance: Efforts to maintain water flow through clearing debris.
  5. Culverting: Converting stream sections into enclosed pipes reduces natural features.
  6. Weirs: Structures built to regulate water flow.
Population Growth & Urbanisation
  • Land Use Change: From rural to urban setups increases impermeable surfaces.
  • Water Demand: Exceeds supply as populations grow, leading to water scarcity issues.
  • Water Conflict: Issues arise around access and equity for available water resources.
  • Privatisation of Water Resources: Increasing trend toward privatizing water supply leading to concerns about equity and access.
Groundwater Issues
  • Groundwater Mining: Unsustainable practices where aquifers are depleted faster than they can recharge.
  • Recharge Rates: Variable depending on climatic and geological conditions.
  • Fossil Water: Groundwater that is not replenished over timescales relevant for human consumption.
Highlighted Water Sources
  • Ogallala Aquifer:
    • Location: Great Plains, USA.
    • Size: One of the world's largest aquifers, supporting 27% of irrigated land in the US.
    • Issues: Over-extraction leads to depletion, quality issues, and possible collapse.

Hydromorphology

Pressures from Human Activity
  • Alteration of Natural Regimes: Dam construction and other modifications disrupt natural water flow regimes.
  • Environmental Injury: Leads to losses in biodiversity, affecting aquatic life and habitats.
  • River Processes: Changes in erosion, transport, and deposition cycles modify river behavior significantly.
Flood Management Strategies
  • Natural Flood Management Approaches:
    • Catchment woodlands and streamside structures can mitigate flood risk.
    • Restoration projects aimed at improving river morphology can help.
    • Agriculture practices, such as cover cropping, can reduce runoff.

Learning Outcomes

  • Manipulation of Water: Understanding various human manipulations and their consequences on waterways.
  • Hydromorphological Pressures: Identifying the pressures created by human management.
  • Consequences Analysis: Outlining effects on hydrological patterns and underlying processes.
  • Evaluating Projects: Weighing the pros and cons of dam, water transfer, and irrigation projects.