Drainage Basins

1. Drainage Basins

2. Definitions Drainage basin: An area of land drained by a single river. Also called the catchment area of a river. Watershed: The dividing line between two drainage basins. Drainage Density: The total length of streams / area of basin.

3. Drainage Basins Source Watershed Confluence point – where tributary meets main river Tributary Main river Catchment Area

4. Drainage Basins Write a definition of the major features of a river basin: • Watershed, source, tributary, confluence, mouth You must also be able to explain the drainage basin system with reference to: • Inputs • Outputs • Transfers • Stores

5. Hydrosphere: River Basins

9. Types of Drainage Patterns

10. Stream Order

12. Write the questions and answers: The drainage basin • What is the area drained by a river called? • What is the line around this that encircles the whole system? Stream ordering • Draw a diagram to show stream ordering and explain what it is used to show. Drainage density • Write out the formula for working out drainage density of a river system. • What factors can affect the drainage density of an area? • What major risk does a high drainage density exacerbate?

13. Hydrosphere Drainage basin as a system • Explain why the river system is an open system. • Make a copy of Fig 3.5 p.41, ensuring to colour code in the key. • What is evapotranspiration? • What is interception? • Name the different ways in which water can be transferred through the system. • What is groundwater and how can it be stored? • Why is baseflow important to stream and rivers during the dry weather? • Describe 2 ways in which runoff occurs.

14. Flows and storm hydrographs • Make a list of the factors that can have a bearing on the discharge of a river. • Define the term discharge. • What is a hydrograph and how and where is the data for it’s construction collected? • Make a copy of fig 3.8. • What is lag time? • Why does it happen? • What can be said about the base flow lag time? • Why is this? • If this rising limb of the graph is steep, what does this mean? • Why do you think that the recessional limb falls less steeply than the rising limb? • What will happen if the bankful discharge level is exceeded? • What becomes the source of water in a river after the storm flow has finished?