001 - Drainage basins

Syllabus Point

Examine (AO3) the functioning of a drainage basin as an open system with inputs, outputs, transfers, stores and feedback loops.

Key Terminology

Define the terms below using your 'IB Geography. Course Book' by Cooke and Nagle, the command term posters in the classroom and the useful links below.

  • Examine
  • Drainage Basin
  • Open System
  • Input
  • Output
  • Transfers
  • Stores
  • Feedback Loops

Useful Links

Activity One - Watch

Watch the following YouTube clip and answer the questions below.

  1. What is a watershed?
  2. How are watersheds linked?
  3. What impact can humans have on watersheds?
  4. How does this clip imply that the drainage basin is an open system?

Activity Two - Draw and Label

Stream Ordering

Watersheds are the dividing line between drainage basins and the size of the drainage basin can be categorised by a concept called stream ordering. Streams which start at the source and don't have any streams joining them are called first order streams. Two first order streams which join make a second order stream. Two second order streams which join make a third order stream and so on. Therefore the higher the stream ordering in a drainage basin the greater the availability of water (generally, remember there are always exceptions).

  1. Draw out the diagram below and mark on the stream orders.
  2. How does this diagram help to explain the idea that a drainage basin is an open system?

Image One - Stream Ordering

Stream Ordering Diagram

Activity Three - Feedback Loops

Feedback loops can be both positive and negative. Negative feedback loops act as a 'check' to the system to help foster an equilibrium. Positive feedback loops are less common and can cause an imbalance, resulting in potentially negative consequences. The image below is an example of positive and negative feedback loops.

Image Two - Feedback Loops

Feedback Loops by Monica Bruckner
  1. Create a systems diagram to show the feedback loops for a drainage basin.
  2. Design a systems diagram to show a positive feedback loop for a drainage basin.


  • An example of a systems diagram - focusing on food.

Image Three - Systems Diagram

Exam Style Question

Construct an open systems diagram for a drainage basin. (4 marks)

Activity Four - Review

If it has been a while since you have studied a rivers based unit. Watch these short YouTube clips to remind yourself of what a drainage basin is along with the key fluvial terminology we will be using throughout this unit. Write down in your glossary the key terminology along with their definitions and then add the terms to the first lessons diagram.

  • Next lesson we will have a terminology test to see exactly what you have remembered. Whoever has the lowest number correct will be our cake baker for the following week!