An Assessment of Streamflow Linkage between Land Use or Land Cover Change and In Lilongwe River Basin, Malawi
World human population has grown very rapidly in the past century. In Malawi‟s Capital City (Lilongwe) it increased by more than 3000% between 1966 and 2008 (from 19,425 to 674,448). Such rapid population growth might contribute to Land Use and Land Cover Changes (LULCC) due to pressure on land resources to meet diverse livelihoods, which in turn significantly affects the flow of water in river catchments. This study was thus conducted to evaluate LULCC in Lilongwe between 1989 and 2004 in view of the exponential population increase, and to assess the effects of LULCC on the streamflow of Lilongwe River. To evaluate LULCC, change detection analysis was carried out on Landsat imagery of the Lilongwe River catchment for the years 1989 and 2004. Data on land cover classifications, soil, rainfall, temperature, elevation and water reservoir levels in the catchment were modelled using the Soil Water Assessment Tool (SWAT) to assess the effects of LULCC on streamflow in Lilongwe River. Results showed that between 1989 to 2004, a 10.7% decrease in forest cover occurred (from 63,112.6 ha to 51,034.3 ha). Furthermore, there was an increase in cropland (8.6%, from 19,249 ha to 28,911.3 ha), and a 3.5% increase in land use for settlement (from 23,535.9 ha to 27,526 ha). The resultant changes in average monthly streamflow were -0.058 m3/s during the dry season (August –November) and +1.432 m3/s during the wet season (December–March). The results establish the link between LULCC and streamflow in the catchment. Integrated catchment management practices are therefore recommended to ensure that further LULCC does not adversely affect streamflow in Lilongwe River, and the livelihoods of its beneficiaries.
Key words: Land use and land cover change, Lilongwe, Lilongwe River, Streamflo, Soil Water Assessment Tool.