This optional theme focuses on water on the land as a scarce resource. It considers the ways in which humans respond to the challenges of managing the quantity and quality of freshwater, as well as the consequences (whether intended or unintended, positive or negative) of management. The theme includes both the physical geography of freshwater (basic hydrology and floods) and human impacts on water quality.

This theme should include the study of at least one detailed case study at the drainage basin level. Reference should be made to additional examples, at a range of scales, in less depth, wherever appropriate.
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1. The water system 3 hours

• The hydrological cycle: Examine the inputs, outputs, stores and transfers of the hydrological cycle. Discuss the causes and consequences of the changing balance between water stored in oceans
and ice.

• The water balance: Explain the concept of maximum sustainable yield of freshwater in terms of a balance between inputs and outputs.

2. Drainage basins and flooding

• Drainage basins: Examine the functioning of a drainage basin as an open system with inputs, outputs, transfers, stores and feedback loops. 2 hours

• Discharge: Define stream discharge. Examine its relationship to stream flow and channel shape. 1 hour

• Hydrographs: Describe the characteristics of a hydrograph. Examine the reasons for spatial and temporal (short term and long-term) variations in hydrographs. Examine the role of hydrographs in forecasting the magnitude, spatial extent and timing of floods. 3 hours

• Floods Discuss: the natural and human causes and consequences of a specific river flood. 3 hours

3. Management issues and strategies

• Dams and reservoirs: Examine the hydrological changes resulting from the construction of dams and reservoirs. Examine the costs and benefits of dams and reservoirs as part of multi‑purpose schemes. 2 hours

• Floodplain management: Explain the stream channel processes (erosion, transport, deposition) and explain the resultant landforms found on floodplains. Examine the human modifications of a floodplain and their effect on the size and probability of floods. Evaluate the costs and benefits of alternative stream management strategies. 3 hours

• Groundwater management: Explain the functioning and management of artesian basins and aquifers, distinguishing between natural and artificial recharge. Examine the environmental impacts of groundwater abstraction. 2 hours

• Freshwater wetland management: Describe the role of wetlands as a water resource. Evaluate the effectiveness of the management strategies that have been adopted in a major wetland. 2 hours

• Irrigation and agriculture: Examine the environmental impact of agriculture and irrigation on water quality: salinization, agro‑chemical run-off, the pollution of groundwater and the eutrophication of lakes, rivers and wetlands. 3 hours

4. Competing demands for water 6 hours

• Conflicts at the local or national scale: Examine the competing demands for water in a specific river basin. Evaluate the strategies that have been adopted to meet these demands.

• Conflicts at the international scale: Discuss an example of an international conflict related to freshwater.