Drainage Basins

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.

Drainage Basins

Watershed

Confluence point – where tributary meets main river

Tributary

Main river

Catchment Area

Source

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

Hydrosphere: River Basins

Types of Drainage Patterns

Stream Order

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?

HydrosphereDrainage basin as a system1. Explain why the river system is an open system.2. Make a copy of Fig 3.5 p.41, ensuring to colour code in the

key.3. What is evapotranspiration?4. What is interception?5. Name the different ways in which water can be transferred

through the system.6. What is groundwater and how can it be stored?7. Why is baseflow important to stream and rivers during the

dry weather?8. Describe 2 ways in which runoff occurs.

Flows and storm hydrographs1. Make a list of the factors that can have a bearing on the

discharge of a river.2. Define the term discharge.3. What is a hydrograph and how and where is the data for it’s

construction collected?4. Make a copy of fig 3.8.5. What is lag time?6. Why does it happen?7. What can be said about the base flow lag time?8. Why is this?9. If this rising limb of the graph is steep, what does this mean?10. Why do you think that the recessional limb falls less steeply

than the rising limb?11. What will happen if the bankful discharge level is exceeded?12. What becomes the source of water in a river after the storm

flow has finished?