A review of the limnology of the Okavango Delta, Botswana

Abstract

Water quantity and quality are important aspects in the management of aquatic ecosystems, including wetlands. This paper has integrated available knowledge from literature on the limnology of the Okavango Delta, Botswana. The current near-natural solute concentrations in the inflow waters can be attributed to low chemical weathering of the quartz basin substrate and nearly absent anthropogenic nutrient sources within the Okavango Delta. The concentration of solutes in endorheic ecosystems is a natural phenomenon. In the Okavango Delta, this concentration is offset by the accumulation of solutes in groundwater beneath numerous treed-islands, due to evapotranspiration by evergreen trees. The freshwater environment has fostered high abundance and diversity of flora and fauna in a semi-arid environment. However, there are several aspects of the Okavango Delta that need more rigorous researched for management purposes. Some of the important knowledge gaps include the role of atmospheric deposition and animal excretion as sources of nutrients and trace elements into the system, and the influence of hydro-period on the distribution of trace elements especially in floodplain sediments, flora and fauna across the Okavango Delta. The issue of bioaccumulation of trace elements is also an important knowledge gap for the Okavango Delta particularly for wildlife and human health.