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Abstract:
Tropical regions are characterized by inconsistent wet and dry rainfall seasons. Water availability in dry seasons is a function of baseflow contributions to the hydrological systems. However, baseflow characteristics are not well understood particularly where they relate to sustaining livelihoods for rural communities, in arid and semi-arid regions. Baseflow timing, quantity and quality have an impact on rural livelihoods and are further complicated by climate change uncertainties. The aim of the study was to identify and quantify natural and anthropogenic basin characteristics that impact on baseflow dynamics and, hence, livelihoods of rural communities. The basin characteristics in the Odzani River catchment of rural Zimbabwe were derived using Geographical Information System tools and hydrological data analysis. Baseflow indices at both monthly and annual time steps were determined using the smoothed minima technique. Pearson Correlation Coefficients between basin characteristics and baseflow indices were determined in order to derive the extent of the possible influence of the basin characteristics on baseflow. From the results, correlations of lineaments density, drainage density, permeability, andesitic/basaltic lithology with annual baseflow indices were 0.56, -0.85, 0.84, and 0.59 respectively. Positive correlations of lineaments density and permeability imply existence of subsurface structures that promote infiltration, recharge and groundwater flow transmission. Drainage density increases drainage surface area that possibly compromises infiltration and recharge. Correlation of monthly precipitation with monthly baseflow index yielded a negative correlation of -0.61 which is attributed to a monthly lag of baseflow response to rainfall received.
