A history of drought in the Murray Darling Basin - factors influencing drought initiation

Worldwide, severe droughts have extensive environmental impacts, such as declined crop yield and livestock production, inadequate water supply and elevated risk of bushfires. Additionally, dealing with drought breaking floods adds significant strain to society and the economy, particularly when businesses and communities are not prepared. Increasing vulnerability to droughts with reduced per capita water storage, particularly in semiarid regions such as the Murray Darling Basin (MDB), Australia, underscores the need for predictive understanding of drought. However, at present, useful forecasts of persistent drought or drought breaking conditions are not yet achievable due to our incomplete understanding of the controls on drought extent and duration. Therefore, to better coordinate drought planning and drought relief activities, it is imperative to understand the factors affecting drought initialisation and cessation. In this paper, the spatial and temporal characteristics of historical droughts (both meteorological and hydrological) that have affected in the MDB are examined. It is shown that historically, drought has varied spatially across the MDB, with significant differences (in terms of timing and severity of drought) between the Upper and Lower MDB. It is also shown that meteorological droughts tend to develop gradually over the MDB, while hydrological drought develops much more rapidly. Further, it is shown that climate drivers of Pacific origin (i.e. El Nino/Southern Oscillation and Interdecadal Pacific Oscillation) play a significant role in drought initiation for the majority of historical droughts since 1900 and, for northern MDB droughts, anomalously cool SSTs off the Northwest of Australia precede all but one of the historical droughts identified. Undoubtedly the reoccurrence of drought places a major strain on the agricultural and water resource management sectors and imposes major economic and social losses. However, with improved knowledge of the climate mechanisms controlling the onset of drought periods, alleviation of the effects may be achieved through improved forecasts and management practices designed specifically to deal with such events.