Morphometry and physical processes of East African Soda Lakes

Abstract

The altitudes of the saline lakes in the East African Rift System (EARS) vary from below sea level in the Danakil Depression (-155 m) to 2000 m in the Ethiopian highlands; most lakes are located above 1000 m. These lakes are among the largest (Turkana) and deepest (Shala) saline lakes in the world, though many formed by volcanism or lahars are small. High concentrations of phytoplankton or suspended sediments lead to high light attenuation, with Secchi visibilities usually less than 1 m. In the shallow, saline lake strong stratification usually develops during the day with mixing to the bottom at night. Seasonal variations in stratification and mixing have been observed in the deep lakes. Topography alters winds and mixing in lakes within volcanic craters. Chemically stratified, saline lakes occur throughout the EARS, and meromixis was documented in Lake Sonachi. Seasonal variations in thermal stratification and horizontal and vertical gradients in salinity occur in Lake Turkana. Only brief visits, occasional year-round studies and long lapses in the study of soda lakes of the EARS leave large gaps in our understanding of temporal variations in their limnology and their responses to climatic and human-caused changes in their hydrology.