Modelling the impact of deforestation on the stream flows - A case of Chalimbana river catchment in Chongwe, Zambia

Sammanfattning: Water is a basic necessity for sustaining life and development of society. Proper management, protection and exploitation of water resources are the challenges imposed by population growth, increasing pressure on the water and land resources by competing usage. A good amount of clean water exists on Earth although it is normally inadequate in supply because of anthropogenic activities such as deforestation and land use change. Like many other catchments that provide economic activities for the community’s livelihood, the Chalimbana river catchment in Zambia has been deforested heavily and most of the local communities believe that deforestation could be the main contributing factor to the drying up of Chalimbana River. The objective of this study was to analyse the impact of deforestation on the stream flow of Chalimbana River Catchment with the help of a conceptual hydrological model, HBV. There was a 24% reduction in the annual average rainfall amounts for the deforested period as compared to the period before deforestation. The Qrec/Qsim ratios had revealed that the annual stream flow generation for the period after deforestation (1987 to 1996) for the Chalimbana River had decreased by about 12% as compared to the period with enough forest cover (1975 to 1985). The ratio of annual Qrec/P had indicated that after a 30% forest loss in Chalimbana catchment, there was a 33% increase in the generation of the stream flow. Based on the results that were obtained, a number of recommendations aiming at improving the catchment management were made.