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Saturday, April 9, 2011

The hydrologic cycle and different drainage patterns

The hydrologic cycle is the journey water takes as it circulates from the land to the sky and back again. It is a conceptual model that describes the storage and movement of water between the biosphere, atmosphere, lithosphere, and the hydrosphere. Water on our planet can be stored in any one of the following major reservoirs: atmosphere, oceans, lakes, rivers, soils, glaciers, snowfields, and groundwater. Water moves from one reservoir to another by way of processes.

Components (processes and terms) of the hydrologic cycle and their definitions:
  1. Evaporationthe process by which water is converted from its liquid form to its vapor form and thus transferred from land and water masses to the atmosphere. 
  2. Precipitation—water falls back to earth from the atmosphere as rain/snow.
  3. Infiltrationthe process by which water on the ground surface enters the soil.
  4. Condensationthe change of the physical state of water from gaseous phase into liquid phase, 
  5. Surface runoffthe water flow that occurs when soil is infiltrated to full capacity and excess water from rain, or other sources flows over the land. 
  6. Evapotranspiration—movement of water from soil and plants to the atmosphere.
  7. Interception—water is intercepted by plants and trees.
  8. Through flow—water that flows horizontally in the soil zone.
  9. Water vapour—gaseous phase of water
  10. The Earth's Water Budget – the distribution of water among the oceans, land and atmosphere.
Putting everything together:
The total quantity of water on the earth remains essentially constant. Water moves about from high ground to low ground, changing location and form (vapor, liquid, solid) as part of the hydrologic cycle. Water vapour in the atmosphere condenses due to the cooler temperature to form clouds (condensation).  Water is delivered to the earth as precipitation (rain or snow) and then seeps into the ground (infiltration) or travels over the ground (surface runoff). Some of the water moving over land or in streams and lakes is lost to the atmosphere as water vapour through evaporation. In addition, plants extract water from the ground and release it to the atmosphere as water vapor (transpiration). Water loss to evaporation and transpiration are referred to collectively as evapotranspiration. Water that has seeped into the soil moves along as through flow and water which runs off to streams moves as stream flow. J

A simple diagram to illustrate the hydrological cycle:

Further Learning on Hydrologic Cycle:

Figure 2: Hydrologic Cycle

A good website for further reading on hydrologic cycle:

Different Drainage patterns

 Dendritic drainage pattern

Trellis drainage patterns

 Radial drainage pattern

Other drainage patterns include: rectangular drainage pattern, parallel drainage pattern, centripetal drainage pattern, deranged/contorted patterns.

A very good website for more information: http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/fluvial_systems/drainage_patterns.html

Thank you. :) Hope you have learnt something.
Yang Yi Chao  JH405  15 :)




  1. thanks Yichao for your posting. after i finish reading this post, i have a better understanding about hydrologic cycle.This Hydrologic Cycle recycles the earth's valuable water supply. In other words, the water keeps getting reused over and over. i want to add in one more point is that the sun actaully plays a very important role in this process as energy in the form of light, and heat causes water to evaporate from oceans, rivers and lakes. without, the sun, hydrologic cycle will not happen.

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  3. Thank you Yichao for the interesting post :) I would like to add on the characteristics for the different drainage patterns mentioned

    Dendritic Drainage Pattern:
    - Develops in regions underlain by homogeneous material. That is, the subsurface geology has a similar resistance to weathering so there is no apparent control over the direction the tributaries take. 
    - Tributaries joining larger streams at acute angles. 

    Trellis Drainage Pattern
    - Develops in folded topography like that found in the Appalachian 
    - Tributaries join the main stream at nearly right angles.  

    Radial Drainage Pattern
    - Develops around conically shaped features as volcanoes.
    - The tributary streams extend the headward reaches upslope toward the top of the volcano.  

    Yangting (10) :D

  4. Hi all, just wanna add an interesting example of a dendritic drainage which I read online :)

    Yemen lies on the edge of one of the world's greatest sand seas (a sand sea is a broad flat area of desert with wind-swept sand, with little or no vegetation). Yet despite this, one can still find the imprints of flowing streams and rivers there, belonging to the drainage basin. The pictures are really pretty :)

    Clarissa (7)