Michael Wrathall

Michael Wrathall

Michael Wrathall, Australia.

Michael Wrathall recently commenced as Manager Knowledge Coordination at the NSW Department of Primary Industries – Water. He has 15 years professional experience in water resource management in the public and private sectors in Australia, the United Kingdom and Samoa. As a senior member of the surface water management team from 2010 to 2017, he was responsible for providing advice on a wide range of complex hydrological issues related to NSW regulated rivers, including critical drought management and assessment of long-term water supply options. His new role involves coordinating the production of technical information within the agency to better target stakeholder needs. He recently graduated from the Science-to-Policy Leadership Program with the Peter Cullen Trust and achieved a Certificate of Excellence from the International Water Centre’s Water Leadership Program. His original qualifications were a Bachelor of Civil Engineering (1st class honours) and Bachelor of Science (Geophysics) from the University of Sydney.

Presentation Title: Drought security assessments of regulated rivers in NSW.

Management of extended drought in NSW has periodically come into sharp focus. Despite the break of the most recent drought in inland NSW in mid-2016, the period since 2001 has been dominated by drought. This study has analysed the management approaches adopted in recent droughts to assess the frequency and duration of historical droughts for all 12 regulated river systems in NSW. The Millennium drought, due to its wide geographical extent and contemporaneity with the implementation of the Water Management Act 2000, has provided an opportunity to better understand the vulnerability to and frequency of drought contingency operations throughout NSW. This was done by comparing the different approaches adopted within each valley during recent droughts and also with reference to the approximately 120 years of historical climate. The historical analysis involved running the long-term surface water models under current development conditions with water sharing plan rules applied. A storage volume ‘trigger’, representing the use of contingency measures in recent drought operations, was identified and then applied retrospectively to the historical record. This created a synthetic history of when such contingency measures should theoretically have been applied over the historical climate. The results elucidated a wide variety of valley-specific findings. Despite the Millennium drought clearly being the most severe on record in southern inland NSW, the critical drought in other NSW valleys was highly variable, as were the management responses. In almost all valleys however, conditions typically improved during late-winter and early-spring, even when low 1 July opening allocations were announced. The results of this analysis can assist in drought management planning of regulated rivers and can be used to identify the most vulnerable townships, allowing targeted infrastructure investment for improvements to water security.

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