Abstract: Lake Chad, on the border of the Sahara desert in central Africa, is well known for its high sensitivity to hydroclimatic events. Over the last 40 years, Lake Chad, once the sixth largest lake in the world, has shrunk by more than 90% in area. In this paper, variations of the open water areas, extracted from multi-source remote sensing data during 1973-2012, are analyzed. The results showed that in general Lake Chad was getting smaller and smaller during 1973-2012. Between 1973 and 1975 its area sharply reduced by about 71%. From then on its area ranges from 2000 km² to 5000 km². In order to validate the reliability of the trends, this paper first compares it with Birkett's results to analyze area accuracy, and next compares the results of MODIS with Landsat and AVHRR to validate the comparability of multi-source data, and last monitors monthly variation of Lake Chad area to validate the feasibility of multi-temporal data. Meteorological data analysis showed that the area of Lake Chad and the fluctuation of annual precipitation were in good correlation. Secondly, a large number of reservoirs built are another important cause of area reduction. Lastly, the Great Barrier that divided the lake into two smaller lakes has made it more vulnerable to water loss.

Key words: Africa, driving mechanism, lake area variation, Lake Chad, remote sensing analysis