Characterisation of the Flow Regime of Ewaso Ngiro North River

Abstract

This study aimed at characterising the river flow regime using statistical and probability methods. Streamflow data for Archers Post river gauging station for the period 1960 to 1998 were used for the analysis. Preliminary analysis of the daily flow data was undertaken to determine monthly mean flow, annual mean flow, 7, 30, 90 and 120 days mean low flow and highest daily discharge (flood flow) for each year. Descriptive statistical parameters including: the mean, standard error, median, standard deviation, coefficient of variation, kurtosis, skewness and confidence level of mean at 95% were computed. The cumulative distribution function of the monthly flow showed that February had the lowest flow and November had the highest. Monthly flow analysis revealed that there were three peaks in April, August and November corresponding to the long, continental and short rainy seasons.