A methodology for developing drought severity-Dration-Frequency (SDF) curves

One of the many ways in preparing for a drought is to carry out a drought risk assessment by characterising the frequency, severity and duration of the drought. The current study aims at developing Severity - Duration - Frequency (SDF) curves to provide a comprehensive characterization of droughts based on monthly precipitation data from 10 selected stations in Victoria, Australia. The drought events were characterized using the Standardized Precipitation Index (SPI) applied to time scales of 12 consecutive months. The SDF curves were developed using the Partial Duration Series (PDS) technique due to many years with no droughts identified in the series. The drought events were selected if they reached the selected SPI drought threshold (i.e. a value of -1 or less). In the study reported herein the minimum 12 month cumulative precipitation below the identified threshold value for 1 month, or consecutive 2, 3 or 4 months drought durations were used for deriving SDF curves. Log Pearson Type III (LPIII) distribution was chosen and fitted well to each of the data series tested. The results of the study would be very helpful in assisting agencies developing drought respond plans or policy makers to plan mitigation measures.