How the congo basin deforestation and the equatorial monsoonal circulation influences the regional hydroloical cycle

ABSTRACT. The Congo basin forest has shown much resilience in size and water yield despite the clearly increasing trends of deforestation in the recent past. The basin is 3.4 million square kilometers in size and its water yield per unit river length is second only to the Amazonian basin, giving it a prominent position in the water stressed continent of Africa. A coupled community climate system of models (CAM3 and CLM3) simulations of the land-surface process in the Congo Basin indicate a reduction in both precipitation and evapotranspiration when the basin is subjected to long term changes of its vegetation-type from forest to savannah grassland. Simulated precipitation, both in the forested and deforested case, reproduces the seasonal characteristics of the observed data The monthly river channel flows also show a marked decrease in empathy with precipitation values. The decrease in these parameters implies a reduced intensity of the hydrological cycle, a phenomenon which is indicative of drought conditions. The model performance in generating and routing runoff through the river channel is still the subject of intensive research and the results obtained here should be seen as part of an iterative process to fine tune runoff parameterization in the CLM, especially surface runoff. A look at the past runoff data for the basin (obtained from the International Research Institute for Climate Prediction database-IRI) indicates gradual, though almost negligible, increasing trend in runoff. While the southward trend in desertification in the Sahara region can not be exclusively attributed to vegetation feedbacks it is nevertheless interesting to investigate why such feedbacks might not have been initiated by the ongoing deforestation of the Congo forest. Long term runoff forecasting for very large basins like the Congo has not been easily amenable to the hydrological techniques of summing up runoff from all the constituent sub-basins. This is more so in the tropical regions where most of the sub-basins are not gauged and therefore lack data in general and are even more deficient in continuous data in particular. The possible use of global climate models to fill this gap would prove to be a useful tool in the management of water resources of such big basins. Since most of these basins are trans-boundary in nature, the global climate models would be handy tools in determining equitable use of water resources in these regions. The results and analysis of the influence of the biosphere-atmosphere interactions on the hydrological cycle in the Congo basin offers a lot of hope for the future management of other large basins in the tropics like the Amazon, the Nile etc.