SPATIAL AND TEMPORAL VARIABILITY OF STREAMFLOW IN CATCHMENTS AREAS OF RWANDA

Abstract

Streamflow represents the integrated response of a catchment to climatic variables, especially rainfall and temperature. This study focused on spatial and temporal variabilityof streamflow in catchments areas of Rwanda (case studies: Sebeya and Muvumba catchments). We used time series and statistical coefficient of variation. Monthly average discharge and monthly rainfall data were collected from 2011 to 2014(4 years). The results for the datasets suggested that the streamflow is largely dependent on rainfall availabilities. In Sebeya catchment, the streamflow variationseems to have been influenced by change in land use and land cover, increase of population density, and the topography and relief of the area because Sebeya catchment is located in a mountainous region. The coefficient of variation is 30.96%, 30.90%,46.61%, 21% in SON, DJF, MAM, JJA respectively and the annual coefficient of variation is 27.77%. However, in Muvumba catchment, the streamflow variation seems to have lower variability as the catchment is located in a flatland area. The coefficient of variation is 11.93%, 18.35%, 20%, 11.95% in SON, DJF, MAM, JJA respectively and the annual coefficient of variation is 4.1%. This low variation is caused by irrigation processes, dam &reservoir construction, and topography of the region. The variation and time series data point out the potential evidence of land use change and their influence on availability of water and sustainability of ecology, energy and agricultural production system across the catchments. Knowing the variabilityof streamflow is a useful information for economic planning studies, hydrological modeling and climate change impact assessment within catchments area of Rwanda. Understanding the processes of changes and predicting the associated impacts, istherefore, important for good management practices to enhance societal resilience.