Like many other countries in Africa’s Sahel region, Mali was flooded on September 15, 2007, when the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured the top image. Heavy rains pushed the converging Niger and Bani Rivers over their banks and filled the surrounding wetlands with water. In this false-color image, made with infrared and visible light, water is black or dark blue, in contrast to the pale tan earth and the bright green plant-covered areas. Clouds are light blue and white.
The lower image was taken on July 25, 2007, before the heaviest rains settled in. Smudges of light blue along the left edge of the lower image are water-soaked ground or extremely muddy water, typical of flooding, indicating that the floods had already started as early as July. The Niger and Bani Rivers, however, were still too small to be seen clearly.
By September 15, the rivers had widened, expanding into pools throughout the wetland. The Niger River remained flooded throughout its entire length, through Mali and Niger, and into Nigeria. A further testament to the rainfall is the greening of the landscape. The wetland in particular went from tan-red, a color typical of recently burned areas where few or no plants are growing, to vivid green. A small red dot in the top image indicates the location of a current fire.
The floods extended far beyond the region shown in this image. As many as 17 countries, including Mali, and more than a million people were affected by flooding across Africa, reported BBC News on September 17. Images of flood areas in Nigeria,Ghana,Senegal, and Sudan are available on the Earth Observatory. Daily images of the entire Sahel are available from the MODIS Rapid Response System.