001 - Drainage Basins

Geographic Knowledge and Understanding

The drainage basin as an open system with inputs (precipitation of varying type and intensity), outputs (evaporation and transpiration), flows (infiltration, throughflow, overland flow and base flow) and stores (including vegetation, soil, aquifers and the cryosphere).

Key Concepts

The physical processes that occur within drainage basin systems are influenced by a wide range of physical and human factors. The power of these influencing factors will affect the system outputs.


  • To be able to explain a drainage basin as an open system.

  • To be able to link the inputs, outputs, flows and stores of a drainage basin system.

  • To be able to define the many inputs, outputs, flows, stores and processes associated with a drainage basin.

Key Terminology

            • Drainage basin

            • Evapotranspiration

            • Aquifer

            • Water Table

            • Transpiration

            • Percolation

            • Input/output/flow/store

Define the words above by using the useful link below and the Freshwater textbook by Codrington. There will be a lot of words learnt throughout the lesson today and the above terms are just a few key ones to get us started.

Useful Links

Activity One - Watch

While completing a unit of study on rivers is quite common place if you come from an IGCSE/GSCE background, if you have completed the MYP it may not be a unit you are familiar with. Due to the lack of familiarity we are going to start with the basics and focus on what is meant by the water cycle. Watch the youtube clip below and describe what the water cycle is. It may help you to draw a diagram.

Activity Two - Draw and Define - Hydrological Cycle

Before we start to investigate rivers it is important to have an understanding of how water flows through the system. The hydrological cycle is a closed system as it has a continual cycle of movement of moisture.

      1. On either an A4 white board or piece of A4 paper write down as many hydrological cycle words that you know, you have 2 minutes. You must also be able to define them!

      2. Copy the diagram below and add the words from activity one on to it. Make sure you have a definition next to the words you haven't heard of before or couldn't remember. You can use your course companion and the following links to help you.

Useful Resources

Flash Card Terms - for the hydrological cycle

USGS - there are way more than you need on this list - so be careful!

Activity Three - Systems

Systems are either classified as open or closed. An open system is when there are clear inputs and outputs. A closed system is when there is a continual cycle, regardless of the speed. The slide share below goes through the concept of a system in detail.

      1. Is a hydrological cycle an open or closed system?

      2. Is a drainage basin an open or closed system?

Activity Four - Draw - Drainage Basin

Your task is to draw an open systems diagram for a drainage basin. Draw this as a flow chart like the example underneath this description (but ignore the letters in it). You need to be using the terms that are in the terminology box below.

Key Terminology

channel flow | troughflowl | throughflow | vegetation storage | percolation | precipitation | surface runoff | channel storage | interception | groundwater storage | infiltration | surface storage | groundwater flow | evaporation x 2 | transpiration

Exam Style Questions

With the aid of a diagram, draw a flow diagram to represent the drainage basin as a system. [6 marks]

This lesson was development in collaboration with Richard Allaway from geographyalltheway. For more resources please visit www.geographyalltheway.com