Tuesday, March 12, 2013

Hydrology on Jeju Island


“The Lung of Jeju”
Cheonjiyeon Waterfall on Jeju Island, South Korea, and one of the most popular tourist attractions on the island.
 
The Gotjawal Forest, located on the middle slopes of Mt. Hallasan is the main groundwater (water that moves in the pore spaces of rock beneath the surface) source for the entire island, a population of 565,000 people.

Covering an area of 86 square miles, the Gotjawal Forest has remained untouched until the mid 20th century. The base of the forest is a mixture of Pahoehoe (smooth, billowy, ropy surface) and ‘A’a (rough, jagged and clinkery surface) lava, both of which were created during the development of Mt. Hallasan

The lava mixture makes for a beautiful landscape. On the other hand, the Pahoehoe and ‘A’a lava have made it difficult to develop the land for agriculture. The rainwater on the island penetrates into their groundwater aquifer (an underground layer of water bearing rock where groundwater can be removed) through the cracks of the Pahoehoe and ‘A’a lava under the forest floor making it the most active aquifer in Korea.
 
(Side view of the aquifer cycle)
This is what happens in Gotjawal Forest when precipitation occurs.
Maintaining a balance of the water usage is essential to avoid drawdown, which is the process of depleting groundwater before it has time to recharge (the replenishing ground water as precipitation allows). This also creates a cone of depression (water levels around the well decrease).By successfully maintaining this balance achieves dynamic equilibrium (the balance between drawdown and recharge).
 
Example of a drawdown pump
and the development of a cone of depression.
The mixture of lava (Pahoehoe and ‘A’a) beneath the forest floor has created a layer of permeable (having pores or openings that permit liquids or gases to pass though) rock. 46 percent of the rainwater that falls over the Gotjawal Forest penetrates the aquifer, because of this there are no rivers on the east and west side of the island. The active aquifer has earned the Gotjawal Forest the nickname “The Lung of Jeju” and has made it unique throughout the region.




Saturated surface of the forest floor.

The Gotjawal Forest was named an Internationally Important Wetland in 2011 under the Ramsar Convention (intergovernmental treaty that works to maintain the ecological character of their Wetlands of International Importance and plan for the sustainable use of all the wetlands in their territories); because it is a habitat for unique plant species and a main source for groundwater.




Indian Pitta
Unfortunately, due to the development of the Gotjawal Forest in the 1980’s for golf courses and resorts researches say that development is the main cause for groundwater exhaustion and pollution. However, the only information shown to support this hypothesis is the decreasing habitats of birds and plant life. There are currently no efforts to protect the streams, plants, or the natural habitats of the birds; even some species like Indian Pittas who are classified as endangered by the Korean Government. 

References:
http://www.jejuweekly.com/news/articleView.html?idxno=301
 

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