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Communication incl. Poster: BibTeX citation key:  Sanou
Sanou, B., Hiernaux, P., Kergoat, L. & Mougin, E. 2009. Spatial redistribution of rainfall water within endorheic land units in Central Gourma (Mali): a remote sensing approach. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: roussot 2009-11-22 21:06:46
Categories: Land surface processes, Water cycle
Keywords: Hydrology
Creators: Hiernaux, Kergoat, Mougin, Sanou
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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Although globaly endoreic, the surface redistribution of rain water over Gourma is complex with two main functional systems. On the sandy soils that extend over about 60% of Gourma landscapes, hydric systems are endoreic with hortonian run-off, operating at short distance, up to a few hundred meters, a few kilometres at most, along the slopes from the top of the dunes to the inter-dune depressions and valleys. On all otherwise textured soils, tallying 40% of Gourma landscapes, hydric systems are also endoreic with hortonian run-off, but operating over much larger distances with concentrated run-off feeding a structured web of rills, gullies and wadies ending in one or several interconnected pools. These soils include rock outcrops and associated erosion surfaces and valleys. Gourma landscapes are made of a mosaic of these two hydric systems.
The objective is to characterise the redistribution of rain water at soil surface through runoff and run on using remote sensing. A first separation of local endorheic system units and endorheic watersheds is based on top soil texture mapped using supervised classification on LANDSAT and SPOT images. Watersheds are further delineated based on topography. Redistribution of rainwater is then assessed through its impact on vegetation growth, by calculating the local anomalies of mean MODIS NDVI values. To avoid the effect of the spatial distribution of rainfall any given year NDVI means were calculated over a series of 8 consecutive wet seasons. As expected, the spatial distribution of rain water is less contrasted in locally endorheic systems, with higher NDVI means and lower standard errors, and extremely contrasted in watersheds that are presenting low NDVI means with high standard errors. The dynamics over time of these pattern is indicative of long term trends in the Sahel ecosystem functioning.
Added by: roussot