GISEPIC AFRICA: A modeling tool for assessing impacts of nutrient and water use in African agriculture

Nearly all of the population growth is expected to occur in the developing countries and all the projections suggest that market demand for food will continue to grow (population growth, higher standard of living, biofuels, etc.), requiring a general increase of food production by 70 % between 2005 and 2050. Food crop production in developing countries will have to almost double to adapt to the new needs. Furthermore, agriculture will have to adopt more efficient sustainable cropping methods to adapt to climate change. Supplying right water and nutrients amount can bring crop yield to higher level in Africa, however possibly affecting the environment including drinking water, soil degradation, deforestation and biodiversity.
In this context, it is of utmost importance to have tools allowing to quickly assess the impact of these potential future agricultural development scenarios on the environment, and more specifically on water availability, water quality degradation and soil.
In this report a GIS system integrating the biophysical continuous simulation model EPIC (Williams et al., 1995) with a geodatabase, GISEPIC AFRICA, is described and tested in the African continent. The GIS system works with a grid of a spatial resolution of 15 km on the whole African continent, integrating daily meteorological, crop land distribution, digital elevation, soil and management data. It allows simulating up to 46 different crops for a period ranging from 1965 to 2006.
The GISEPIC AFRICA system was used to spatially assess environmental impacts of different agriculture scenarios on water and soils by assessing nitrogen leaching and runoff losses. The comparison of different management scenarios pointed out a potential increase of the environmental impact on water and soil and highlighted the importance of irrigation practices influencing environmental impact of different scenarios: it was shown how irrigation practices can bring to a more sustainable production reducing water stresses and allowing the crops to uptake efficiently the nutrients available in the soil or added with fertilizer, which are no longer available for leaching or transport with surface runoff.