Base flow Separation using Exponential Smoothing and its impact on Continuous Loss estimates

Rainfall runoff models are used to estimate design floods. These models require several inputs such as, rainfall duration, intensity, loss etc. For baseflow separation in design flood estimation the estimation of continuing loss (CL) is vital. The surface runoff has to be separated from the stream flow hydrograph. To obtain the volume of surface runoff, the use of an appropriate baseflow separation method is essential and in this paper an exponential method is used to assess the impact of baseflow on continuing loss estimates. The sensitivity analysis shows that the required baseflow separation coefficient (α) could be estimated using 3 to 5 rainfall streamflow events from the study catchment. The selected α can then be applied to other rainfall streamflow events of the same catchment to observe the sensitivity on continuing loss estimate. It has been observed that a small degree of error in the selection of α value does not significantly affect the estimates of the CL values. Rather than using complex rules, the method and procedure used in this research for baseflow separation can be used to estimate α for all other Queensland catchments. Corresponding author: Dr G A Tularam, Griffith University, Griffith School of Environment, Nathan Campus, Kessels Rd, Brisbane 4111; Email: [email protected]: Tel: 0410649736 Fax: 617 37357459