Using satellite-derived rainfall data the accumulated amount of rainfall in the Upper Niger Basin during the current wet season is calculated (yellow line), and compared to rainfall in the past. This graphs shows whether the rainfall in the current season so far is relatively high or low.
The flooding of the Inner Niger Delta depends on the river flow of the Niger and Bani Rivers, which in its turn depends on the rainfall in the Upper Niger Basin. The flow of the Bani and Niger River, and thus also the flooding of the Inner Niger Delta, is determined by the rainfall in the Upper Niger Basin upstream of the Inner Niger Delta, thus in the eastern part of Guinea-Conakry and the SW part of Mali. The rainfall in this area in July-August is therefore a good indicator of the flooding of the Inner Niger Delta 3-4 months later. The daily estimated rainfall (see Recent rainfall) of the Upper Niger Basin is used in OPIDIN to improve the prediction of the flood level. In these calculations, the daily rainfall in the Upper Niger Basin is converted to km3 water.
The basic information is derived from satellite images and made available through various websites (see Recent rainfall and Current rainy season). The graph above shows this information from 1 April onwards in comparison to the rainfall over the same seven months during previous years (2001 - last year).