Climate driver informed short-term drought risk evaluation

This study proposes a methodology for quantifying the impact of climate drivers on water supply drought risk. Climate driver informed short-term drought risks are evaluated for future time steps following conditioning on the initial state of climate drivers and initial reservoir storage level. The methodology is demonstrated using a case study in eastern Australia. Simulations of future rainfall are provided by the climate-informed multitime scale stochastic (CIMSS) model, which is used to incorporate Pacific decadal variability exhibited by the Pacific Decadal Oscillation-Interdecadal Pacific Oscillation. The climate driver informed drought risks are compared to a traditional approach that evaluates longterm drought risks using a nonclimate driver informed rainfall model. The case study considers four scenarios describing a range of different climate driver initial conditions. For the PDO-IPO positive initial state scenarios, the short-term risks are found to be higher than traditional long-term risks by 20%–100%. Furthermore, the elevated short-term risks can last up to 30 years with the CIMSS model but <10 years with the traditional model. The implication of these results is that traditional approaches can significantly underestimate the severity and duration of drought risk. The case study demonstrates a practical and general approach for incorporating the influence of climate drivers and initial storage conditions into drought risk analyses, which could be adapted to other regions and climate drivers. The results prompt a recommendation to water resource planners to carefully integrate climate variability over a range of time scales into water supply system planning and operation.