Land cover change analysis within the GLOWA Volta basin in West Africa using 30-meter Landsat data snapshots

Quantifying the effects of land cover change is imperative to improve future hydrological budget estimates within large river basins or catchments. However especially in Africa, rigorous, regional standardized and spatially explicit land cover change data is missing, or often inconsistent and outdated. Within the GLOWA Volta hydrological project in West Africa, we used 26 Landsat tiles from the years 1990 and 2000/2001 respectively to analyze land cover change within the 400.000 km2 sized Volta basin. The Landsat tiles were augmented with daily and well corrected 250-meter MODIS time-series observations, for the period from 2000 onwards. The Land Cover Classification System (LCCS) legend from the Food and Agricultural Organization (FAO) was used for the land cover descriptors and the change mapping. Socio-economic data from Ghana was used to verify the satellite change vector for selected ´hot spots´ areas. Between 1990 and 2000/2001, 18 percent of the total land cover were transformed from woodland with additional shrubs to herbaceous vegetation, 15 percent were modified from closed woodland (40-95% tree cover density, TC) to a open woody vegetation (15-40% TQ, and 10 percent were transformed from closed woodland (40-95% TC) to herbaceous vegetation. Land cover conversion and modifications can be mapped effectively and efficiently using 30-meter Landsat and standard LCCS descriptors, in conjunction with socio economic data.