EXTENDED ABSTRACT The main objective of this paper is to present a model for generating synthetic rainfall totals on various timescales to be applicable for a variety of uses. Many large-scale ecological and water resources models require daily, monthly and yearly rainfall data as input to the model. As historical data provides only one realisation, synthetic generated rainfall totals are needed to assess the impact of rainfall variability on water resources systems A model for generating yearly totals will be described using traditional time series methods. This model, along with a similarly constructed daily generation model by, We present a new model for the generation of synthetic monthly rainfall data which we demonstrate for Parafield in Adelaide, South Australia. The rainfall for each month of the year is modelled as a non-negative random variable from a mixed distribution with either a zero outcome or a strictly positive outcome. We use maximum likelihood to find parameters for both the probability of a zero outcome and the gamma distribution that best matches the observed probability density for the strictly positive outcomes. We describe a new model that generates correlated monthly rainfall totals using a diagonal band copula with a single parameter to generate lag-1 correlated random numbers. Our model preserves the marginal monthly distributions and hence also preserves the monthly and yearly means. We show that for the particular example of Parafield the correlation between rainfall totals for successive months is not significant and so it is reasonable to assume independence. This is however not true for daily rainfall. The correlation between rainfall on successive days is certainly small but it is reasonable as suggested by The City of Salisbury supplies recycled stormwater to local businesses on a commercial basis and it is important that they understand the full implications of the likely distribution of rainfall and the consequent impact on their ability to manage the capture, treatment and supply to consumers of recycled water. Recent work b
