The Watershed
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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.
Definitions:
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).
Drainage Basin Feedback
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| Click on the image to learn more about feedback loops within a drainage basin. |
Discharge
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.
Tasks:
1) Complete the activity from Geographyalltheway. Click on the banner below.
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:
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| Diagram from coolgeography.co.uk |
Urban Hydrology:
