Relationships between water level at hydrological stations and inundated area in the River Niger Inner Delta, Mali

The River Niger Inner Delta is a wide natural seasonal flood plain in Mali, where the two main streams of the River Niger gather. This area is only poorly influenced by hydraulic managements, thus the inundation dynamic is mostly natural. Many people live in this humid area, and their activities depend on the date of arrival of the flood peak, and of its duration. But the Inner Delta is very large, and there is a long delay of several weeks or months between the arrival of the flood at the Delta entry, and the occurrence of the flood at its exit. Previous studies using the low resolution AVHRR/NOAA14 satellite data, over the years 1990-2000 described the space-time propagation of the flood and of the inundated vegetation cover. These images help to study the relationships between the inundated areas and the water levels at several hydrological gauging stations, which have data series long enough and which cover several regions inside the Delta. The values of flooded areas obtained from both regional and local approaches are close, but always greater for the local approach. The results seem closer to the observations with the regional approach. Finally, we propose the reconstruction of possible past flooded areas from these relationships.