DEVELOPMENT OF REGIONAL FLOW DURATION CURVES FOR SELECTED RIVERS IN UPPER NIGER RIVER BASIN, NIGERIA

Abstract

It is common knowledge that the end user of stream flow data may necessarily not have any prior knowledge of the quality control measures applied in their generation. Thus, this study provides an intuitive attempt to provide an independent quality indicator to boost the confidence in the use of stream flow data by developing regional flow duration curves for selected ungauged station of the upper Niger River Basin, Nigeria. Toward this end, stream flow data for seven gauging stations covering some sub-river basin in the upper Niger River Basin was effectively mobilised; in this case, monthly stream flow data covering a range of eleven to fifty three years period. The flow duration curves from the gauging stations were fitted with three distribution models; i.e., the logarithmic, power and exponential regression equations. For regionalisation, the parameterisation was carried out in terms of the drainage area alone; just for simplicity of models. Results obtained showed that the exponential regression equation, in terms of R2 had the best fit. Though the regionalised model was simple, measurable agreement was obtained during the calibration and validation phases. However, considering the length of data used and probable variability in the stream flow regime, it is not possible to objectively generalise on the quality of the results. Against this backdrop, it suffices to take into cognisance the need to use an ensemble of catchment characteristics in the development of the flow duration curves and the overall regional models; this is important considering the implications of anthropogenic activities and hydro-climatic variations.