Abstract
Lake Chad, in the Sahelian zone of west-central Africa, provides food and water to ~50 million people and supports unique ecosystems and biodiversity. In the past decades, it became a symbol of current climate change, held up by its dramatic shrinkage in the 1980s. Despites a partial recovery in response to increased Sahelian precipitation in the 1990s, Lake Chad is still facing major threats and its contemporary variability under climate change remains highly uncertain. Here, using a new multi-satellite approach, we show that Lake Chad extent has remained stable during the last two decades, despite a slight decrease of its northern pool. Moreover, since the 2000s, groundwater, which contributes to ~70% of Lake Chad’s annual water storage change, is increasing due to water supply provided by its two main tributaries. Our results indicate that in tandem with groundwater and tropical origin of water supply, over the last two decades, Lake Chad is not shrinking and recovers seasonally its surface water extent and volume. This study provides a robust regional understanding of current hydrology and changes in the Lake Chad region, giving a basis for developing future climate adaptation strategies.
Highlights
Lake Chad, in the Sahelian zone of west-central Africa, provides food and water to ~50 million people and supports unique ecosystems and biodiversity
Recent studies showed that the amount of water extraction in the 1980s and 1990s was probably overestimated as the quantity of water abstracted for human activities was negligible compared to the lake volume change[9]
Times series and anomaly of the surface water extent of Lake Chad derived from multi-spectral MODIS images show that the southern pool area is quite stable over the last two decades, with a nearly flat linear trend, meaning that its water surface current has not been affected by drastical changes since 2000s (Fig. 2)
Summary
Binh Pham-Duc 1,2*, Florence Sylvestre1*, Fabrice Papa 3,4, Frédéric Frappart 3, Camille Bouchez 5 & Jean-Francois Crétaux[3]. Due to the decrease in number of hydrometeorological gauge stations and difficulties to obtain data consistently and accurately from remote regions, we combine complementary information from different satellite observations, e.g. optical imagery from MODIS and multi-missions satellite altimetry from Topex-Poseidon, Jason-1, 2, 3, ENVISAT and SARAL in order to reconstruct surface water extent and level of the Lake Chad (see Methods) This multi-sensor approach is important because it allows to better evaluate the open water surface compared to the surface covered by vegetation, which is one of the main question when applying remote sensing techniques in the context of shallow lakes, especially the Lake Chad[14]. It is a shallow lake (
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