SURFACE WATER FEATURES IN CARBONATE ISLAND KARST LANDSCAPES: SMALL OCEANS INSIDE A SMALL ISLAND

Hydrologic regimes on small carbonate islands are frequently linked to tides. This is demonstrated in the small, inland ponds on San Salvador Island, Bahamas where water levels vary on time scales similar to those of the ambient tide. The water level variations at each pond display unique magnitude and timing characteristics. These unique signatures can be valuable in unraveling the complex hydrology within the karst landscapes of this small island.

A preliminary investigation was conducted to analyze such phenomena across five hydrologic features in the northeast part of the island. Water levels from these features were recorded in the field using a digital water level logger during a one week period. Four of these features were inland ponds in close proximity, which demonstrated water level variations that mimicked tidal cycles. Water levels within a flank margin cave, located between the ponds and the ocean, were also recorded and included for comparison. The water level variations observed in each feature were found to be distinct with respect to timing and magnitude, and a correlation between the feature surface area and variation magnitude was investigated. Conclusions from this study suggests the following: surface area and magnitude may not be related, these features have a complex hydrologic relationship with the ocean, and are unlikely to be directly linked via the shallow subsurface. From this investigation a strategy for applying similar methodology, to a more extensive analysis utilizing longer time series with elevation control, can be developed to further elucidate the characteristics of small carbonate island karst hydrology.