Rainfall data at fine time scale are required for erosion modelling of small landscapes such as railway and road embankments. Limited availability of such data leads to the option of daily rainfall disaggregation. Daily rainfall data can be gathered easily from various sources. One of these sources is the Australian SILO Data Drill facility that generates continuous daily rainfall data from 1889 to current date for any set of coordinates on the Australian continent. This paper is concerned with the relationship between daily and fine simulation timescale variance required by a daily rainfall stochastic disaggregation model [1]. For Queensland, it is found that the relationship between the daily and six- minute variances exhibit a well pronounced seasonality. Incorporation of the seasonality of the variance relationship into the stochastic disaggregation model significantly improved the performance of the model in terms of the reproduction of the different aggregation level statistics.