Environmental Studies AS - The hydrosphere (The properties of water…
Environmental Studies AS - The hydrosphere
The properties of water
Unusual expansion, usually applied to water, which expands as it is cooled below 4°C.
Water molecules in ice are less densely packed than when they are in liquid form so solid ice floats of liquid water.
Floating solid ice prevents warmer water below from freezing.
'General physiological solvent' as most biological reactions occur with solutes dissolved in water.
Plant nutrients and most materials transported in blood and sap are dissolved in water.
Changes of state:
The shape of water molecules and the way electrons are arranged allow negative parts to form weak bonds with positive parts of other molecules.
Bonds produce groups of up to four molecules that behave like a larger molecule with a higher boiling point.
Narrow temperature range allows the hydrological cycle to occur.
High heat capacity:
Water heats up and cools down slowly.
Helps maintain climatic stability by moderating temperature changes
The hydrological cycle
The transfer of water between reservoirs:
Water is a renewable resource but human actions alter water movement rates in the cycle, depleting resources.
- The average length of time that a molecule remains in a reservoir.
The main processes involved in the hydrological cycle:
Parts of the hydrological cycle that are on/in the ground are of greatest direct importance to humans.
Three parts of the cycle.
River channel discharge.
Temperature and humidity control.
Hydrological cycle is driven by solar power, which warms the Earth's water
Makes it evaporate and rise in the atmosphere as the energy is converted into gravitational potential energy.
Converted to kinetic energy as it falls to the Earth and flows back to the sea.
Solar energy also drives evaporation from the land and the plants that lose water by transpiration.
Water as a resource
Water use and conflicts of interest
Conflicts about water use may be caused in two ways:
Abstracting and storing water can cause problems for other users of the water or of the surrounding area.
Other user groups in the area may threaten the water supplies.
Water quality requirements:
Heavy metal concentrations
E. coli abundance
Sources of water
Main features that affect the usefulness of a river are:
Total annual water flow (river discharge).
Level of natural contaminants.
Pollutants from human activities.
Existing land use.
The environmental effects of reservoirs:
Changes in river flow.
The main features of aquifers:
Suitable geological structures.
The consequences of aquifer overuse:
Changes in surface hydrology.
Flocculation/coagulation and clarification.
Activated carbon filters.
Demand for water
Factors that cause the demand for water to change:
Change in population size.
Change in living standards.
Changes in attitude to water use.
Global water supplies:
Availability of water, affluence and development are interconnected issues.
Poor countries/communities may not be able to afford to purify water.
More affluent societies can afford to exploit water for a more comfortable lifestyle and more industries.
Overexploitation of water resources may reduce amount of water left for poorer sections of society.
Water conservation and management
Better distribution of water:
Reducing distribution losses.
More efficient use of water:
Low water-use appliances.
Recycling: 'grey water' use.
Increasing the availability of water: