Endorheic Lake Ike-Hanna
December 10, 2010
Geologic basins usually develop outlets to the sea by riparian (water following gravity) erosion. Endorheic basins are geologic depressions that have not developed an outlet to the sea. The only way water can leave such a basin is by evaporation into the air above or by seepage into the rock below. Endorheic lakes form when endorheic basins fill with water from surrounding streams or local rains. Well-known examples include the Great Salt Lake and the Caspian Sea, the latter being the largest lake on Earth. If inflow exceeds seepage and evaporation, the lake grows. During prolonged dry periods, endorheic lakes can completely disappear, leaving behind salt pans or playas.
The coastal city of Gonaives, where Haiti's independence from France in 1804 was initiated, lies within the watershed of Haiti's longest river, the Artibonite. The city is surrounded by rugged deforested hills and has been severely flooded during periodic storms and hurricanes, as torrential rains are shed by the surrounding denuded hills and the Artibonite overflows. Just south of the city lies a frequently dry endorheic basin.
In September of 2008, Haiti was struck by Hurricanes Ike and Hanna within days of each other, causing massive flooding and killing hundreds of people in Gonaives. This episode left a large, new endorheic lake in the basin. The new body of water was named after the causative storms by local people. For weeks, Lake Ike-Hanna was linked with the sea before becoming a separated body of water. During these weeks, breeding populations of several fish species entered the new endorheic lake. The level of Lake Ike-Hanna has been slowing dropping since 2008, although supplemented by major tropical cyclonic rains, such as those associated recently with Hurricane Tomas. If other such rains do not come along for several years, Lake Ike-Hanna will eventually succumb to seepage and evaporation. In the interim, locals have developed a small fishing industry, as seen in the above photo -- taken in July 2010.
Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot SD1000; Focal Length: 17.4mm; Aperture: f/4.9; Exposure Time: 0.0008 s (1/1250); ISO equiv: 200; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (Auto); Color Space: sRGB.