IB Environmental Systems and Societies (HL) - Topic 4: Water

Hydrological cycle

Interconnected system where water moves through the atmosphere while going through different phases, including storages and flows.

Storages

Where water is stored when not actively moving through the water cycle, examples include organisms, soil, oceans, water vapor, surface waters, ice caps/glaciers, and aquifers.

Flows

Movement of water from one storage to another via flow routes, can be transformations (change in state) or transfers (change in location).

Evaporation

Liquid water becomes gas after being heated, removing salt and minerals.

Transpiration

Plants absorb water through roots and release water vapor through stomata.

Condensation

Gas water becomes liquid due to cooling, forming clouds or dew.

Advection

Movement of water vapor/droplets/clouds by wind.

Infiltration

Water seeping through soil layers to become groundwater.

Groundwater flow

Movement of water through soil/rocks to reach groundwater reservoirs.

Freshwater

Only 2.5% of Earth's water, some like groundwater considered non-renewable due to slow renewal.

Water stress

Demand for water exceeds supply or quality makes it unusable, exacerbated by climate change.

Desalination

Process of making saltwater suitable for drinking, often done in dry regions with cheap energy access.

Aquaculture

Controlled farming of aquatic organisms to meet seafood demand, with benefits like local economy support and drawbacks like habitat destruction.

Overfishing

Excessive fishing leading to reduced biodiversity and harm to marine ecosystems.

Water pollution

Contamination of water sources by industrial waste, wastewater, mining activities, marine dumping, oil spills, fossil fuel burning, chemicals, and metals.

Eutrophication

Excessive nutrients causing algae blooms, leading to oxygen depletion and dead zones.

Water quality measurements

Include salinity, pH, temperature, dissolved oxygen, turbidity, and biodegradability.

Biochemical oxygen demand (BOD)

Measure of oxygen needed to decompose organic waste in water, high BOD levels indicate pollution.

Buffer zone

Areas around sensitive zones like water sources to prevent pollutants from agricultural land from reaching them.