COMPARISON OF 4 LOSS MODELS FOR TIME-SERIES ANALYSIS OF RAIN FALL STREAMFLOW DYNAMICS

Four rainfall loss modules are compared within an overall catchment-sc ale (lumped) rainfall-streamflow modelling methodology which requires data only for basin rainfall, streamflow and air temperature. A common feature of the loss modules is the internal simulation of a temporall y variable catchment wetness index; effective rainfall in a given time interval is essentially the product of rainfall, the catchment wetnes s index and a volume-forcing constant appropriate for the model calibr ation period. The comparison, which employs daily data for an approxim ately 3-y period for the 601 km(2) catchment of the Exe at Thorverton in southwest England, provides insight to how sensibly, in terms of ex pected basin-scale behaviour, the different loss modules simulate catc hment wetness. Because of its restricted scope (one 3-y year period fo r one catchment) the comparison does not, however, enable recommendati on of a best loss module for general application. Reference is made to the results from an independent comparison of the same, or very simil ar, loss modules which spanned several modelling periods for two catch ments but without investigating how the internally calculated catchmen t wetness index varied. Suggestions are made concerning the developmen t and evaluation of loss modules for specific objectives.