ESTIMATION OF RECHARGE AND RUNOFF VOLUMES FROM UNGAUGED CATCHMENTS IN EASTERN AUSTRALIA

A model has been developed to estimate runoff volumes from generally available geophysical data. Most of the hydrological processes are modelled in a realistic manner and the model needs only one fitting parameter. Input to the model consists of monthly rainfall, evaporation and parameters. In the model, rainfall is partitioned, depending on soil water status, into soil water storage, groundwater recharge and surface runoff. Surface runoff and baseflow are separate outputs of the model and equal emphasis has been placed on estimating each of these flow components. To do this a technique has been developed for estimating recharge. The model has been shown to reproduce observed monthly flows in eastern Australian streams very well, both on catchments used to calibrate the model and in independent tests where it was used without any local calibration data. This ability to provide good estimates of volumes of flow on ungauged catchments with very modest requirements for input data means the model could find wide application. The evidence of accurate estimation of runoff volumes in an independent test in a wide range of climatic and geophysical environments is suggested to result from the physical realism of the model.