Stepwise development of a two-parameter monthly water balance model

It has recently been shown that the structures of monthly water balance models can be very parsimonious. In this paper, we describe how a new two-parameter rainfall-flow model was developed using a stepwise approach. A sample of 410 basins representing a wide range of climate conditions from semi-arid through temperate to tropical humid was used to develop the new model, on the basis of previous work on a four-parameter daily rainfall-flow model. Comparisons with several well-known models showed that the new structure is efficient and provides valuable insight into the rainfall-flow transformation at a monthly time-step.