The Watershed

  • What are the main functions of the watershed/drainage basin?

  • How can humans influence the functioning of the system?

Open and Closed Systems

Open System – is a system that transfers both matter and energy can cross its boundary to the surrounding environment. Most ecosystems are example of open systems.

Closed System – is a system that transfers energy, but not matter, across its boundary to the surrounding environment. Our planet is often viewed as a closed system.

Drainage Basin flow chart.jpg


Complete this worksheet using the definitions below.

_processes_in_a_drainage_basin (1).docx

Percolation: When water travels from unsaturated ground into saturated ground.

Interception: When an object (building, tree) stops precipitation reaching the ground beneath.

Transpiration: Liquid water evaporating from vegetation.

River discharge: Eventually most rivers enter the sea and discharge the river’s flow into the sea.

Groundwater flow: The movement of water through saturated ground.

Channel flow: Water that is travelling in rivers or streams.

Surface run-off (overland flow): When water travels across the surface of the earth

Stem flow: When intercepted water then travels down the branches and trunks of vegetation.

Evaporation: Liquid water from surface stores and rivers turning into water vapour (gas).

Surface storage: Any water that is held on the surface of the earth e.g. lake or pond. Some surface stores like puddles may only be temporary.

Infiltration: When water travels from the surface of the earth into the ground beneath.

Groundwater storage: Water that is stored in saturated ground.

Throughflow: The movement of water through unsaturated ground.

Canopy drip: Intercepted water dripping off vegetation onto the ground.

Soil-moisture storage: Water that is stored below the surface in unsaturated ground.

Precipitation: Any moisture that falls from the sky e.g. rain or snow.

Positive and Negative Feedback

Positive feedback mechanisms enhance or amplify some initial change, while negative feedback mechanisms stabilize a system and prevent it from getting into extreme states. In many respects, the history of Earth’s climate system can be seen as a bit of a battle between these two types of feedbacks, but in the end, the negative feedbacks win out and our climate is generally stable with a limited range of change (excepting, of course, a few extremes such as the Snowball Earth events back around 750 Myr ago).

positive and negative feedback.png

Drainage Basin Feedback

drainage basin feedback.png
Click on the image to learn more about feedback loops within a drainage basin.


River discharge is the volume of water flowing through a river channel. This is the total volume of water flowing through a channel at any given point and is measured in cubic metres per second (cumecs).

The discharge from a drainage basin depends on precipitation, evapotranspiration and storage factors.

Drainage basin discharge = precipitation – evapotranspiration +/- changes in storage.


1) Complete the activity from Geographyalltheway. Click on the banner below.
Geographyalltheway banner.png

2) Go to the Geographypods page and scroll down to the discharge section and complete tasks 1&2. Once you have done this do the homework task as well.


Hydrographs A level.jpg

Hydrographs Factors.jpg
Diagram from

Urban Hydrology:


effect of urbanization1 (1).jpg

83 storm hydrograph.pdf