Background: In arid region the river runoff is mainly consequence of rainfall over the river catchment
area. Surface water discharge and base flow from the tributaries or other water sources e.g. lake, pond,
glacier melting etc. also influences the river runoff. However, the way of contribution of rainfall and water discharge
from other sources are dissimilar to impart river runoff.
Method: In this paper simulation study of rainfall and runoff data of Kulfo River of Southern Ethiopia is carried
out. Descriptive statistical and graphical techniques are used to comprehend and identify the inherent characteristics
of raw data of river runoff and associated rainfall. The twenty years rainfall and runoff time series of Kulfo
River is used to develop Transfer Function Model which is then after used to forecast the river runoff. The
overall performance of the model was evaluated using statistical model evaluation criteria and working out the
error statistics between the observed river runoff and model forecasts.
Results: The results of runoff forecasting of Kulfo River for the next two year indicates that transfer function
model performs excellently. The model results are outstanding to meet the mean river discharge and concurrently
well capture the high and low values of runoff.
Conclusion: Stochastic Transfer Function Model based upon the analysis of Time Series of Rainfall and River
Runoff is an efficient tool for forecast of River runoff, quantification of River discharge, flood warning etc.