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Ch 4 : Water, Food Production Systems and Society

Ch 4 - Water, Food Production Systems and Society

4.1 - Introduction to Water systems

  • Hydrological cycle: system of water flows and storages that may be disputed by human activity

    • energy from solar radiation driven this cycle

  • Water budget: quantitative estimate of the amount of water in storages and flows of the water cycle

    • Renewable resources: atmosphere, rivers

    • Non-renewable resources: oceans, icecaps

    • Middle group: groundwater aquifers

Human impact on the water cycle:

  1. Withdrawals: domestic use, irrigation in agriculture and industry

  2. Discharges: by adding pollutants to water

  3. Changing speed at which water can flow and where it flows

  4. Diverting rivers or sections of rivers

  • Transfers: occur when it stays in the same state:

    • Flooding

    • Surface runoff

    • Stream flows and current

  • Transformations: when it changes state to and from water:

    • Evaporation: liquid to water

    • Condensation: water vapour to liquid

    • Freezing: solid snow to ice

  • Ocean currents: are movements of water both horizontally and vertically

    • have an important role in energy discharges that influence changes

  • Surface currents: moved by the wind

    • earth’s rotation deflects them and increases their circular movement

  • Deep water currents (thermohaline currents): influenced by the oceanic conveyor belt

    • difference in water density (salt and temperature)

    • warm water vs. cold water

    • movement of water (warm and cold)

  • Cold ocean currents run from poles to the equator, warm water currents flow from the equator to the poles

  • Water has higher specific heat capacity (amount of heat needed to raise the temperature of the unit of matter by 1 degree celsius)


Ocean currents and climate:

  1. Affects location in terms of climate

  2. Difference temperature and whether

  3. Land close to seas and oceans has mild climate with moderate winters and cool summers

4.2 - Access to Freshwater

  • Access to an adequate supply of freshwater varies widely

    • Climate change may disrupt rainfall patterns and further affect thus access

  • Demand for freshwater increases as population, irrigation and industrialization increases

  • Freshwater supply may become limited

  • Scarcity of water resources can lead to conflict between human populations especially when resources are shared

Humans use freshwater for:

  1. Domestic purposes used at home

  2. Agriculture, irrigation for animals

  3. Hydroelectric power generation

  4. Transportation

  5. Making boundaries between nation rivers

Sources of freshwater:

  1. Surface freshwater

  2. Underground aquifers (water can be extracted from surface or wells)

    • Freshwater conflict:

      • climate change distributing rainfall patterns (causing inequalities)

      • irrigation which leads to soil degradation

    • Solutions:

      • increase freshwater supplies by reservoirs, desalination plants rainwater and harvesting

      • irrigation: select drought resistant crops

  • Irrigation: results in soil degradation especially in dry areas

    • Our water supply is sufficient, however, like food, distribution is uneven

  • Salinization: process of naturally dissolving minerals in the top layer  of the soil which makes it too salty (saline) for further agriculture

4.3 - Aquatic Food production systems

  • Continental shelf: extension of continents under the seas and oceans (creates shallow water)

    • has 50% of oceanic productivity but 15% of its area

    • light reaches shallow seas so producers can be photosynthesize

    • countries can claim, exploit, and harvest it

  • Zooplankton: single-celled animals that eat phytoplankton and their waste

  • Fishery: when fish are harvested in a certain way

    • 90% oceans and 10% freshwater

    • 70% of the world’s fisheries are exploited

  • Aquaculture: farming aquatic organisms (coastal and inland) involving interventions in the rearing process to enhance production

    • Impacts of fish harms: loss of habitat, pollution, spread of diseases, escaped species may survive to interbreed with wild fish, escaped species may autocomplete native species

  • Maximum Sustainable yield (MSY):

    • SY: increase in natural capital (natural income that can be exploited each year without depleting original stock)

    • MSY: highest amount that can be taken without permanently deleting the stock

4.4 - Soil degradation and conservation

  • Pollutants can be: anthropogenic or natural, point or nonpoint source, organic or inorganic, direct or indirect

    1. Organic

      • pollutant: sewage, animal waste, pesticide

      • example: human waste, insecurities

      • effects: eutrophication, loss of biodiversity

    2. Inorganic:

      • pollutant: nitrates and phosphates radioactive material, heavy toxic material

      • example: industry, nuclear power stations, fertilisers

      • effects: eutrophication, bioaccumulation, biomagnification

    3. Both:

      • pollutant: solid domestic waste, debris, suspended solids

      • example: silt form construction, household garage

      • effects: damage controls, plastics

  • Freshwater pollution: agricultural runoff, sewage, solid domestic waste

  • Marine pollution: rivers, human pollution, pipelines

Measuring water pollution:

  1. BOD: amount of dissolved oxygen required to breakdown organic material in a given volume of water

  2. Indicator species: plants and animals that show something about the environment by their presence, absence, abundance

  3. Biotic index: indirectly measures pollution by assessing the impact on species within the community according the their tolerance, diversity, and relative abundance

  4. Eutrophication: when lakes and coastal waters receive inputs of nutrients (nitrates and phosphates) that result in an excess growth of plants and phytoplankton

  • The eutrophication process:

    • Fertiliser enters rivers/lakes

    • High level of phosphates, algae grows faster

    • More algae, more food for zooplankton or small animals that feed on them. A lack of zooplankton animals means that these are less to eat algae

    • Algae die and are decomposed by aerobic bacteria

    • Not enough oxygen is present therefore everything dies and the food chain collapses

    • oxygen levels fall lower, dead organic material sediments on the lake or the river bed and turbidity increases

    • All life is gone and sediment settles to leave a clear blue lake. This process in which bodies of water become enriched with nutrients and minerals

  • Biochemical oxygen demand: amount of DO required to break down organic material in a given volume of water

    • biological monitoring and indicator species can be used to determine levels of pollution

    • strengths: stationally, sensitive and representative

    • weaknesses: identification

Ch 4 : Water, Food Production Systems and Society

Ch 4 - Water, Food Production Systems and Society

4.1 - Introduction to Water systems

  • Hydrological cycle: system of water flows and storages that may be disputed by human activity

    • energy from solar radiation driven this cycle

  • Water budget: quantitative estimate of the amount of water in storages and flows of the water cycle

    • Renewable resources: atmosphere, rivers

    • Non-renewable resources: oceans, icecaps

    • Middle group: groundwater aquifers

Human impact on the water cycle:

  1. Withdrawals: domestic use, irrigation in agriculture and industry

  2. Discharges: by adding pollutants to water

  3. Changing speed at which water can flow and where it flows

  4. Diverting rivers or sections of rivers

  • Transfers: occur when it stays in the same state:

    • Flooding

    • Surface runoff

    • Stream flows and current

  • Transformations: when it changes state to and from water:

    • Evaporation: liquid to water

    • Condensation: water vapour to liquid

    • Freezing: solid snow to ice

  • Ocean currents: are movements of water both horizontally and vertically

    • have an important role in energy discharges that influence changes

  • Surface currents: moved by the wind

    • earth’s rotation deflects them and increases their circular movement

  • Deep water currents (thermohaline currents): influenced by the oceanic conveyor belt

    • difference in water density (salt and temperature)

    • warm water vs. cold water

    • movement of water (warm and cold)

  • Cold ocean currents run from poles to the equator, warm water currents flow from the equator to the poles

  • Water has higher specific heat capacity (amount of heat needed to raise the temperature of the unit of matter by 1 degree celsius)


Ocean currents and climate:

  1. Affects location in terms of climate

  2. Difference temperature and whether

  3. Land close to seas and oceans has mild climate with moderate winters and cool summers

4.2 - Access to Freshwater

  • Access to an adequate supply of freshwater varies widely

    • Climate change may disrupt rainfall patterns and further affect thus access

  • Demand for freshwater increases as population, irrigation and industrialization increases

  • Freshwater supply may become limited

  • Scarcity of water resources can lead to conflict between human populations especially when resources are shared

Humans use freshwater for:

  1. Domestic purposes used at home

  2. Agriculture, irrigation for animals

  3. Hydroelectric power generation

  4. Transportation

  5. Making boundaries between nation rivers

Sources of freshwater:

  1. Surface freshwater

  2. Underground aquifers (water can be extracted from surface or wells)

    • Freshwater conflict:

      • climate change distributing rainfall patterns (causing inequalities)

      • irrigation which leads to soil degradation

    • Solutions:

      • increase freshwater supplies by reservoirs, desalination plants rainwater and harvesting

      • irrigation: select drought resistant crops

  • Irrigation: results in soil degradation especially in dry areas

    • Our water supply is sufficient, however, like food, distribution is uneven

  • Salinization: process of naturally dissolving minerals in the top layer  of the soil which makes it too salty (saline) for further agriculture

4.3 - Aquatic Food production systems

  • Continental shelf: extension of continents under the seas and oceans (creates shallow water)

    • has 50% of oceanic productivity but 15% of its area

    • light reaches shallow seas so producers can be photosynthesize

    • countries can claim, exploit, and harvest it

  • Zooplankton: single-celled animals that eat phytoplankton and their waste

  • Fishery: when fish are harvested in a certain way

    • 90% oceans and 10% freshwater

    • 70% of the world’s fisheries are exploited

  • Aquaculture: farming aquatic organisms (coastal and inland) involving interventions in the rearing process to enhance production

    • Impacts of fish harms: loss of habitat, pollution, spread of diseases, escaped species may survive to interbreed with wild fish, escaped species may autocomplete native species

  • Maximum Sustainable yield (MSY):

    • SY: increase in natural capital (natural income that can be exploited each year without depleting original stock)

    • MSY: highest amount that can be taken without permanently deleting the stock

4.4 - Soil degradation and conservation

  • Pollutants can be: anthropogenic or natural, point or nonpoint source, organic or inorganic, direct or indirect

    1. Organic

      • pollutant: sewage, animal waste, pesticide

      • example: human waste, insecurities

      • effects: eutrophication, loss of biodiversity

    2. Inorganic:

      • pollutant: nitrates and phosphates radioactive material, heavy toxic material

      • example: industry, nuclear power stations, fertilisers

      • effects: eutrophication, bioaccumulation, biomagnification

    3. Both:

      • pollutant: solid domestic waste, debris, suspended solids

      • example: silt form construction, household garage

      • effects: damage controls, plastics

  • Freshwater pollution: agricultural runoff, sewage, solid domestic waste

  • Marine pollution: rivers, human pollution, pipelines

Measuring water pollution:

  1. BOD: amount of dissolved oxygen required to breakdown organic material in a given volume of water

  2. Indicator species: plants and animals that show something about the environment by their presence, absence, abundance

  3. Biotic index: indirectly measures pollution by assessing the impact on species within the community according the their tolerance, diversity, and relative abundance

  4. Eutrophication: when lakes and coastal waters receive inputs of nutrients (nitrates and phosphates) that result in an excess growth of plants and phytoplankton

  • The eutrophication process:

    • Fertiliser enters rivers/lakes

    • High level of phosphates, algae grows faster

    • More algae, more food for zooplankton or small animals that feed on them. A lack of zooplankton animals means that these are less to eat algae

    • Algae die and are decomposed by aerobic bacteria

    • Not enough oxygen is present therefore everything dies and the food chain collapses

    • oxygen levels fall lower, dead organic material sediments on the lake or the river bed and turbidity increases

    • All life is gone and sediment settles to leave a clear blue lake. This process in which bodies of water become enriched with nutrients and minerals

  • Biochemical oxygen demand: amount of DO required to break down organic material in a given volume of water

    • biological monitoring and indicator species can be used to determine levels of pollution

    • strengths: stationally, sensitive and representative

    • weaknesses: identification

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