Recession flow analysis of the Blue Nile River

Estimates of the amount of recession flow can be derived from streamflow records. Such estimates are critical in the assessment of low flow characteristics for the Blue Nile River, from which about two‐thirds of the irrigation requirements in Sudan are satisfied. The recession flow hydrograph can be estimated by fitting the conceptual non‐linear storage outflow model using an iterative algorithm. An analytical model to forecast the Blue Nile recession flow is developed and the performance of the model is compared to the previous Blue Nile recession flow model. In the proposed model, a simple linear regression equation is introduced to illustrate the effect of antecedent flow on the recession parameter. Results indicate that the model can provide a simple and reliable method to predict the recession flow of the Blue Nile River. Copyright © 2003 John Wiley & Sons, Ltd.