Lake Chad vegetation cover and surface water variations in response to rainfall fluctuations under recent climate conditions (2000−2020)

• Published in: The Science of the total environment 2023-01, Vol.857, p.159302-159302, Article 159302
• Main Authors: Gbetkom, Paul Gérard, Crétaux, Jean-François, Tchilibou, Michel, Carret, Alice, Delhoume, Manon, Bergé-Nguyen, Muriel, Sylvestre, Florence
• Format: Article
• Language: English
• Subjects: Lake Chad; Rainfall; Sahel; Spatiotemporal changes; Surface water levels; Vegetation cover
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.159302

Monitoring the evolution of the Sahelian environment is a major challenge because the great Sahelian droughts, marked by significant environmental consequences and social impacts, contributed, for example, to the drying up of Lake Chad. We combined remote sensing images with a water level database from the Hydroweb project to determine the response of Lake Chad vegetation cover and surface water variations to rainfall fluctuations in the Lake Chad watershed under recent climate conditions. The variance in lake surface water levels was determined by computing the monthly anomaly time series of surface water height and area from the Hydroweb datasets. The spatiotemporal variability of watershed rainfall and vegetation cover of Lake Chad was highlighted through multivariate statistical analysis. The spatial distribution of correlations between watershed rainfall and Lake Chad vegetation cover was investigated. The results show an increase in watershed rainfall, vegetation cover, and surface water area and height, as their slopes were all positive i.e., 5.1 10−4 (mm/day); 4.26 10−6 (ndvi unit/day); 1.2 10−3 (km2/day) and 6 10−5 (m/day), respectively. The rainfall variations in the watershed drive those of Lake Chad vegetation cover and surface water, as the rainfall trend was strongly and positively correlated with those of vegetation cover (0.79), surface water height (0.57), and area (0.53). The time lag between the watershed rainfall fluctuations and lake surface water variations corresponded to approximately ∼112 days. Between rainfall variations and vegetation cover changes, the spatial distribution of the time lag showed a response time of 64 days in the marshlands of the southern basin. For the analysis of lakes around the world, this research provides a robust method that computes the spatiotemporal variances of their trends and seasonality and correlates these with the spatiotemporal variances of climate changes. The correlations obtained have strong potential for predicting future changes in lake surface water worldwide. [Display omitted] •Rainfall increase has improved the water level and vegetation cover of the lake.•August rainfall is an important climate indicator in the Lake Chad watershed.•Surface waters of Lake Chad vary to rainfall changes with a 112-day time lag