Friday, October 7, 2016

Hydrology of the Kalahari Desert: With specific focus on the difference in groundwater recharge, rainfall, and erosion in the landscape, between the separate regions of the desert



The Kalahari Desert is considered a semi-arid savanna, with a clear wet and dry season. Despite the seasons, much variation in the hydrology of this location can be found when analyzing the different regions of the desert, specifically the outskirts, and the heart of the Kalahari. The groundwater recharge in the Kalahari Desert today is measured at about 5 mm a year towards the edges of this location, and as little as 1 mm a year in the central region of the desert. 


http://www.photocircle.net/eu/photos/dennis-wehrmann/15361-Kalahari-Desert-Sunrise-Namibia



The difference in groundwater recharge that is seen throughout the different areas of the desert correlates to the amount of rainfall measured at the edges of the Kalahari, compared to the center. Over 400 mm of annual rainfall has been recorded towards the outskirts of the desert, with a much lower precipitation rate, less than 350mm, at the center.


Maps showing the location of the Kalahari Desert in Southern Africa, the heart of the desert towards the lower left side of Botswana 

https://www.pinterest.com/pin/558376053770450237/
https://www.pinterest.com/pin/380343131003168965/


Thus a pattern in the hydrology of the Kalahari Desert emerges, with consistent high groundwater recharge near the edges, and significantly lower recharge near the center.

Because of this pattern, we see landscapes closer to the borders of the desert reflecting that of a high infiltration capacity environment, with more vegetation, and a very dry, arid landscape of low infiltration capacity towards the middle.



Examples of landscapes on the outskirts of the Kalahari, with more vegetation as a result of more rainfall

http://2.bp.blogspot.com/-ZcZ52MoG2eE/VSZLMOXumkI/AAAAAAAADRs/Tr8Io4IM4Ns/s1600/roadsidewater1.jpg
http://dave--kelly.blogspot.com/2010/05/amadwala-lodge-khama-rhino-sanctuary.html
http://www.xflow.eu/en/2015/08/17/kalahari-desert-botswana/




Examples of drier more arid landscapes towards the center of the Kalahari

http://geograph-sarah.blogspot.com/2010/02/kalahari-desert.html
http://www.authorstream.com/Presentation/12dagati-149523-kalahari-desert-marr-entertainment-ppt-powerpoint/
https://www.pinterest.com/wayne1948/namibia-africa/



With less rainfall being absorbed by the earth in certain parts of the desert, one can observe erosion in the form of rills and gullies, as rainfall runs off quickly into streams.



Examples of rills and gullies, in dendritic drainage patterns, in the Kalahari as a result of rainfall in Low Infiltration Capacity areas

http://media.gettyimages.com/photos/aerial-view-of-kalahari-desert-northern-cape-province-south-africa-picture-id475155325?s=170667a
https://www.pinterest.com/pin/87960998942992427/
http://www.answers.com/Q/What_landforms_are_found_in_the_Kalahari_desert?#slide=1



Although some humans, like the San People, live near the outskirts of the desert, due to the extreme conditions of the Kalahari, the landscape is not very suitable for humans, as the annual rainfall in each region struggles to support the vegetation and wildlife alone. An increase in the groundwater table would provide more suitable conditions for human accommodation, but such a thing would require an extreme and consistent annual rainfall increase.


Some of the San People of the Kalahari Desert 

https://en.wikipedia.org/wiki/San_people
http://www.dailymail.co.uk/femail/article-2590781/Meet-women-make-Bear-Grylls-look-like-wimp-The-people-Namibias-ancient-San-tribe-REAL-ultimate-survivors.html

Interesting Video outlining where the Kalahari gets it's little moisture from. One way the groundwater table might increase in the future, providing more rainfall for the Kalahari, would be if the Maloti Mountains in Lesotho were to erode away.

https://www.youtube.com/watch?v=f_96xW6eF1Q




References:

http://www.hydrology.nl/images/docs/dutch/key/De_Vries_Groundwater_Recharge_Kalahari.pdf
https://www.britannica.com/place/Kalahari-Desert
https://ucdenver.instructure.com/courses/342696/files/3965142?module_item_id=898889