ESS – Unit 4 Notes
4.1 - Introduction to Water Systems
Significant Ideas:
The hydrological cycle is a system of water flows and storages that may be disrupted by
human activity.
The ocean circulatory system (ocean conveyor belt) influences the climate and global
distribution of water (matter and energy).
Knowledge and Understanding:
Solar radiation drives the hydrological cycle.
Fresh water makes up only a small fraction (approximately 2.6% by volume) of the Earth’s
water storages.
Storages in the hydrological cycle include organisms, soil and various water bodies, including
oceans, groundwater (aquifers), lakes, rivers, atmosphere, glaciers and ice caps.
Flows in the hydrological cycle include evapotranspiration, sublimation, evaporation,
condensation, advection (wind-blown movement), precipitation, melting, freezing, flooding,
surface runoff, infiltration, percolation, and streamflow or currents.
Human activities such as agriculture, deforestation and urbanization have a significant
impact on surface runoff and infiltration.
Ocean circulation systems are driven by differences in temperature and salinity. The
resulting difference in water density drives the ocean conveyor belt, which distributes heat
around the world, and thus affects climate.
The Earth’s Water Budget
Only about 2.5% of the Earth’s water is fresh water. The other 97.5 per cent is sea water. Most of
the world’s fresh water is in the form of ice – ice caps and glaciers. This accounts for about 70 per
cent of the world’s fresh water. Most of the rest of the world’s fresh water is in the form of
groundwater. Fresh-water lakes and rivers account for only about 0.3 per cent of the global fresh
water budget. There is also some fresh water contained in the soil and in the atmosphere. The
following diagram shows the distribution of fresh water resources.
4.2 – Access to Fresh Water
Significant Ideas:
the supplies of freshwater resources are inequitably available and unevenly distributed,
which can lead to conflict and concerns over water security.
freshwater resources can be sustainably managed using a variety of different approaches.
Knowledge and Understanding:
access to an adequate freshwater supply varies widely.
climate change may disrupt rainfall patterns and further affect this access.
as populations, irrigation and industrialization increase, the demand for fresh water
increases.
freshwater supplies may become limited through contamination and unsustainable
abstraction.
4.1 - Introduction to Water Systems
Significant Ideas:
The hydrological cycle is a system of water flows and storages that may be disrupted by
human activity.
The ocean circulatory system (ocean conveyor belt) influences the climate and global
distribution of water (matter and energy).
Knowledge and Understanding:
Solar radiation drives the hydrological cycle.
Fresh water makes up only a small fraction (approximately 2.6% by volume) of the Earth’s
water storages.
Storages in the hydrological cycle include organisms, soil and various water bodies, including
oceans, groundwater (aquifers), lakes, rivers, atmosphere, glaciers and ice caps.
Flows in the hydrological cycle include evapotranspiration, sublimation, evaporation,
condensation, advection (wind-blown movement), precipitation, melting, freezing, flooding,
surface runoff, infiltration, percolation, and streamflow or currents.
Human activities such as agriculture, deforestation and urbanization have a significant
impact on surface runoff and infiltration.
Ocean circulation systems are driven by differences in temperature and salinity. The
resulting difference in water density drives the ocean conveyor belt, which distributes heat
around the world, and thus affects climate.
The Earth’s Water Budget
Only about 2.5% of the Earth’s water is fresh water. The other 97.5 per cent is sea water. Most of
the world’s fresh water is in the form of ice – ice caps and glaciers. This accounts for about 70 per
cent of the world’s fresh water. Most of the rest of the world’s fresh water is in the form of
groundwater. Fresh-water lakes and rivers account for only about 0.3 per cent of the global fresh
water budget. There is also some fresh water contained in the soil and in the atmosphere. The
following diagram shows the distribution of fresh water resources.
4.2 – Access to Fresh Water
Significant Ideas:
the supplies of freshwater resources are inequitably available and unevenly distributed,
which can lead to conflict and concerns over water security.
freshwater resources can be sustainably managed using a variety of different approaches.
Knowledge and Understanding:
access to an adequate freshwater supply varies widely.
climate change may disrupt rainfall patterns and further affect this access.
as populations, irrigation and industrialization increase, the demand for fresh water
increases.
freshwater supplies may become limited through contamination and unsustainable
abstraction.
