CALIBRATION OF A MODIFIED SFB MODEL FOR 25 AUSTRALIAN CATCHMENTS USING SIMULATED ANNEALING

Simulated annealing is used to calibrate a conceptual rainfall-runoff model (a modification of Boughton's SFB model) by fitting modelled mon thly runoff to historical data. The problem to be solved is that of fi nding the global minimum of a multivariate function that has many extr aneous local minima, a situation in which conventional optimisation me thods are ineffective. The model estimates runoff from daily rainfall and daily potential evaporation estimates for a catchment. The 25 catc hments used for the study cover a wide range of climatic types, includ ing humid tropical, humid subtropical, arid, semiarid, Mediterranean a nd marine west-coast. The catchments differ in the number and type of model processes activated, which is indicated by the parameters fitted . A parsimonious approach was adopted where only the sensitive model p arameters for a catchment were fitted. The objective function which qu antifies discrepancies between the computed and observed streamflows w as carefully selected to satisfy the least squares assumptions. Finall y, a case study is presented to illustrate the fitting process and hig hlight some of the difficulties that may be encountered. It is shown t hat simulated annealing is able to fit six or seven sensitive paramete rs of the modified SFB model by locating the global minimum of the obj ective function. (C) 1997 Elsevier Science B.V.