The long-term trends in hydro-climatology of the Dinder and Rahad basins, Blue Nile, Ethiopia/Sudan

This paper examines the long-term trends of streamflow, rainfall and temperature over the Dinder and Rahad River basins. Streamflow of the Rahad River showed significant increasing trends in both the annual and seasonal flows. There was no detectable change in the mean annual and seasonal flow patterns of the Dinder. However, the analysis of seasonal maxima suggested a shift towards decreased flows during the high flow period (August) and increased flows during the low flow period (November). The Dinder maxima of August decreased from 517 m³/s over the early part of the record (1972–1991) to 396 m³/s over the latest years (1992–2011). The mean annual temperature showed significant increasing trends at the rate of 0.24 and 0.30°C/decade in the examined stations. Rainfall showed no significant change. The result of this study suggests other factors than climate variability (e.g., land use and land cover changes) to be responsible for streamflow alterations.