Monthly versus daily water balance models in simulating monthly runoff

SummaryA monthly water partition and balance model, Wapaba, based on the Budyko framework model is introduced and applied to over three hundred Australian catchments. The model uses consumption curves to partition water to a number of components according to supply and demand and to represent spatial and temporal heterogeneity of catchment processes in a parsimonious formulation. The Wapaba model was benchmarked against the well known abcd monthly water balance model as well as the original monthly Budyko framework model and found to outperform both on the Australian catchments. The Wapaba model was also compared with two daily water balance models widely used in Australia. It had validation performance comparable to or better than the daily water balance models in simulating monthly runoff on the Australian catchments. This indicates that the monthly model has not been disadvantaged for not using the within-month temporal sequences of the forcing variables. The finding supports the use of monthly water balance models for applications where one is primarily interested in monthly, seasonal and annual streamflow volumes or where daily input data are not readily available.

► We introduced a monthly water partition and balanced (Wapaba) model.
► It outperformed two other monthly models on 331 Australian catchments.
► It performed comparably or better than two daily water balance models.
► The monthly model has not been disadvantaged for not using daily inputs.
► The finding supports the use of monthly models for a range of hydrological applications.