A sub-continental scale assessment of lake-climate interactions in sub-Sahelian Africa

Africa is considered to be extremely vulnerable to climate change despite contributing little, and yet this vulnerability does not resonate with the breath or depth of research on the region, particularly regarding its inland freshwater systems. While lakes support million of livelihoods through several water uses supply, limnological studies in Sub-Sahelian Africa have largely focused on a few well-studied lakes, leaving vast regions underexplored.

 

Existing global studies on climate-change impacts on lake water quality and freshwater availability often operate at broad scales. However, such efforts rarely address sub-continental heterogeneity or provide the foundational climatological baselines. The first step of any global-scale study is the definition of the average seasonal behavior of any geophysical or geochemical variable considered. This being just an intermediate step towards more advanced analysis (e.g. detection of trends and anomalies, extremes detection), the climatology itself has generally received little attention. In ungauged regions where local in-situ data are scarce, identifying the drivers of ecological shifts is more challenging as a knowledge base on the average or past conditions of the lake is unavailable.

 

In this study, we present the first atlas of lake functioning across sub-Sahelian Africa, identifying regional clusters of climate and ecological analogs. We analyze the interplay between lakes and their surrounding environment -encompassing both climatic and anthropogenic drivers. Our results reveal three main regions of analogous lake functioning, where key climatic drivers interact with lake response in terms of water availability and water quality. These interactions are shaped by overarching processes (such as large-scale atmospheric circulation) as well as lake-specific conditions, such as morphological characteristics, climatic zones, human pressures like land use and population density.

By exploring the potential role of remote sensing to overcome data scarcity in sub-Sahelian African lakes, our study provides the first multivariate assessment of average lake-climate interactions and provides a baseline for future research in this region, in support of an informed monitoring of the lakes, a more sustainable management of water resources, and climate risk mitigation actions.