1.  Before break, we discussed watersheds and what constitutes a watershed. How do you think water moves through a watershed?

2. The Drainage Basin as a system 12/3/13

5. A drainage basin  An area of land drained by a river and its tributaries where any precipitation is collected or drained into it.  It’s boundary is marked by a ridge of high land called a watershed  Drainage basins have one main stream and many tributaries  Each tributary of main stream forms sub-drainage basin

6.  What is the difference between a drainage basin and a watershed?

7. Watershed: A stretch of land that surrounds drainage basin Drainage Basin: A river system that collects rainwater and comprises of streams and river Tributaries: Streams that flow in the river which is mainly found in the upper course Distributaries: Branch out from the river which is mainly found in the river delta River Source: Point where the river starts River Mouth: Place where the river meets the sea / ocean or the river ends

8.  A drainage basin may be described as an open system.  It forms part of the hydrological cycle/ water cycle

9. Characteristics of a drainage basin are:  Inputs : in the form of precipitation  Outputs: water is lost through evapotranspiration  Within the system, some of the water:  Is stored in water storage such as lakes or soil  Passes through a series of transfers or flow e.g. infiltration, percolation, etc.  terms we will learn in a moment

10. Important terms  Interception : precipitation lands on vegetation  Infiltration : Water that reaches ground surface will soak into soil.  Overland flow : water moving over the ground.  Percolation : Some water sinks deep into the earth through openings in the soil.  percolate= gradually filter through the ground; trickle  Stemflow : water that flow down tree trunks or plant stems.

11.  Input  Storage  Transfer  Output

12.  main input – precipitation in the form of: rain, snow, hail, sleet, etc.  Factors affecting the amount of water in the system:  the intensity,  the duration and  frequency  Each subsystem of the drainage basin system will also have  inputs and outputs, and  the output from one stage of the diagram will form the input for another

13.  How are all drainage basins connected?

14.  Water stored - on the surface, - in lakes and channels or - in the groundwater store.  Some water will be stored in the soil and rock.  The amount of water stored will vary depending on:  the porosity of the soil and  the permeability of the rock.  Water can be temporarily stored via interception. – in the storage of water on leaf and plant stems.

15.  all the water flowing over the drainage basin’s surface is called runoff.  made up of streamflow - flow through permanent river channels and overland flow or surface runoff  Overland flow - transfers water through the basin either as:  sheetwash across the surface, or  in tiny channels called rills

16.  final release of the water in a drainage basin  flow into the sea will be the main output of a drainage basin.  Some water will also be lost via evapotranspiration.  Evaporation from water bodies and soils  Transpiration from plants