Introduction to water on Atolls
There are over 50,000 small tropical islands in the Pacific , Indian and Atlantic Oceans with around 8000 of these inhabited. These small islands are formed as sand cays, coral atolls or small elevated limestone islands (White et al, 2007). Atolls composed of small shallow islands surrounding a shallow lagoon (Bailey et al, 2010). Very small surface area, low elevation and in some cases high population density leads to a strain on water resources (White et al, 2007; Bailey, 2010). Islands rely on rainwater collection and a freshwater lens (Hunt, 1996). This freshwater lens is an unconfined aquifer under the island with fresh water floating on top of the denser saltwater (Terry and Falkland, 2010).
The image bellow displays how a fresh water lens functions:
Fresh water Ideas For a Thirsty Planet..., (2009). Climate change and freshwater part 4...freshwater challenges of Islands. [online] Available at: https://shipbright.wordpress.com/2009/11/09/climate-change-and-freshwater-part-4-freshwater-challenges-of-islands/ [Accessed 6 May 2015].
The reple
nishment of this freshwater lens is dependant on on rainwater and also the geology of the island (Terry and Falkland, 2010). The vegetation types of such islands have adjusted to the hydrological settings on atolls such as coconut trees (developed to be phreatophytic) which uses shallow ground water to supply most of their moisture demands (Terry and Falkland, 2010).
However fresh water lens's are not always reliable and there are many natural causes for fresh water lens depletion;
- Physical erosion of the island (powerful storms or rising sea levels)
- Drought reduces freshwater recharge
- Lens salinisation caused by storm surges or large waves (Terry and Falkland, 2010)
Water Management problems faced by atoll islands
Most Pacific Island States to tackle problems with water management such as:
- Small population (relative to a work force however many have a large population relative to an area)
- Lack of resources
- Susceptibility to natural disasters
- Excessive dependance on international trade
- High transportation and communication costs
- Costly administration and infrastructure
- Lack of large businesses
Lack of resources and economic stability in developing countries means low levels of water infrastructure and maintenance (Keen, 2003).
In the following posts I will be posting about some case studies and problems in water management faced on atoll.
References:
White, I., Falkland, T., Perez, P., Dray, A., Metutera, T., Metai, E. and Overmars, M. (2007). Challenges in freshwater management in low coral atolls. Journal of Cleaner Production, 15(16), pp.1522-1528.
Freshwater Ideas For a Thirsty Planet..., (2009). Climate change and freshwater part 4...freshwater challenges of Islands. [online] Available at: https://shipbright.wordpress.com/2009/11/09/climate-change-and-freshwater-part-4-freshwater-challenges-of-islands/ [Accessed 6 May 2015].
Bailey, R., Jenson, J. and Olsen, A. (2010). Estimating the Ground Water Resources of Atoll Islands. Water, 2(1), pp.1-27.
Terry, J. and Falkland, A. (2009). Responses of atoll freshwater lenses to storm-surge overwash in the Northern Cook Islands. Hydrogeology Journal, 18(3), pp.749-759.
Hunt, C. (1996). Property rights and environmental management on Pacific atolls. Int J of Social Economics, 23(4/5/6), pp.221-234.