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Topic 4: Water

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  1. 4.1 Water systems

    1. • Solar radiation and gravity • Heat for evaporation, gravity for drainage

    2. • System with stores and flows • Stores: boxes; flows: arrows

    3. • Oceans (96.5%), glaciers/ice caps (1.7%), groundwater (1.7%) • Surface freshwater (0.02%), atmosphere (0.001%), organisms (0.0001%)

    4. • Transpiration, sublimation, evaporation, condensation, advection, precipitation • Melting, freezing, run-off, infiltration, percolation, streamflow, groundwater flow

    5. • Agriculture, deforestation, urbanization alter flows and stores • Reduced evapotranspiration, increased run-off → flash floods

    6. • Flow diagrams of inputs and outputs • Calculate sustainable harvesting rates

  2. 4.2 Water access, use and security

    1. • Access to sufficient safe drinking water • Component of sustainable societies

    2. • Social, cultural, economic, political factors • Impact availability and equitable access

    3. • Population growth or economic development • Uses: domestic, irrigation, livestock, industry

    4. • Dams, reservoirs, rainwater catchment, desalination plants • Natural wetland enhancement

    5. • Physical scarcity: limited abundance • Economic scarcity: limited storage/transport systems

    6. • Metering, rationing, grey-water recycling • Low-flush toilets, rainwater harvesting

    7. • Food production systems • Greenhouses, aquaponics, drip irrigation, drought-resistant crops

    8. • Country-specific management strategies

  3. 4.3 Aquatic food production systems

    1. • Phytoplankton: microscopic photosynthetic plankton • Macrophytes: visible aquatic plants

    2. • Organisms from freshwater and marine environments

    3. • Human population growth, dietary preference changes

    4. • Bottom trawling, ghost fishing, poisons, explosives

    5. • Dramatic, lasting stock decrease • Example: Newfoundland cod

    6. • Highest annual catch sustainable over time • Used to set fishing quotas

    7. • Ocean acidification • May cause population collapse in aquatic ecosystems • Example: coral bleaching

    8. • Policy legislation for fishing industry • Consumer behaviour changes • Permits, quotas, seasons, mesh size, zones, labelling

    9. • Support food chains, maintain sustainable yields • Provide shelter and spawning grounds

    10. • Farming of aquatic organisms • Expanding for food supply and economic development • Impacts: habitat loss, pollution, disease spread, escapees

  4. 4.4 Water pollution

    1. 4.4.1Water pollution sources

      • Sewage, agricultural run-off, industrial effluent • Urban run-off, solid waste disposal, oil spills

    2. 4.4.2Plastic debris accumulation

      • Marine environments • Oceanic gyres, microplastics enter food chain

    3. 4.4.3Water quality measurement

      • Chemical, physical, biological characteristics • Water quality index (WQI) • Parameters: dissolved O₂, pH, temperature, turbidity, nitrates, phosphates, metals

    4. 4.4.4Biochemical oxygen demand (BOD)

      • Dissolved oxygen required by microorganisms for decomposition • mg O₂ per litre in 5 days at 20°C

    5. 4.4.5Eutrophication

      • Mineral nutrient inputs (nitrates, phosphates) • Excessive phytoplankton growth (algal blooms)

    6. 4.4.6Eutrophication sequence

      • Impacts and changes to aquatic system

    7. 4.4.7Eutrophication and ecosystem services

      • Eutrophication can substantially impact ecosystem services • Eutrophication can affect services associated with fisheries, recreation, aesthetics and health

    8. 4.4.8Eutrophication management levels

      • Eutrophication can be addressed at three different levels of management • These three levels of management are: • the reduction of human activities that produce pollutants—e.g., alternatives to current fertilizers and detergents • the reduction of the release of pollution into the environment—e.g., treatment of wastewater to remove nitrates and phosphates