Understanding hydroclimate processes in the Murray-Darling Basin for natural resources management

Abstract

Abstract. Isolating the causes of extreme variations or changes in the hydroclimate is difficult due to the complexities of the driving mechanisms, but it is crucial for effective natural resource management. In Australia's Murray-Darling Basin (MDB), ocean-atmosphere processes causing hydroclimatic variations occur on time scales from days to centuries, all are important, and none are likely to act in isolation. Instead, interactions between all hydroclimatic drivers, on multiple time scales, are likely to have caused the variations observed in MDB instrumental records. A simplified framework is presented to assist natural resource managers in identifying the potential causes of hydroclimatic anomalies. The framework condenses an event into its fundamental elements, including its spatial and temporal signal and smallscale evolution. The climatic processes that are potentially responsible are then examined to determine possible causes. The framework was applied to a period of prolonged and severe dry conditions occurring in the southern MDB from 1997-2010, providing insights into possible causal mechanisms that are consistent with recent studies. The framework also assists in identifying uncertainties and gaps in our understanding that need to be addressed.

Trends in synoptic circulation and precipitation in the Snowy Mountains region, Australia, in the period 1958–2012

“…Both are proposed as mechanisms for increasing summer precipitation in SEA (Gallant et al 2012;Shi et al 2008;Cai et al 2005).…”

“…5a). A number of years (1965, 1967, 1982 and 2006) stand out as having fewer precipitation days ≥ 10 mm and coincide with periods of below average rainfall related to El Niño events (Gallant et al 2012) in addition to a positive IOD event in 1967. Similarly, 1974Similarly, , 1975Similarly, and 1992 …”

“…However, by considering a multidecade period, this work allows short-term, drought-related trends to be placed in the context of longer-term climate variability. The period chosen for this study encompasses anthropogenic climate forcing (Reisinger et al 2014;Gallant et al 2012). Mean teleconnection values for each synoptic type provide insight into the complexity of determining the contribution of each teleconnection to precipitation in the Snowy…”

Links between the Big Dry in Australia and hemispheric multi-decadal climate variability – implications for water resource management

“…For example, in SWWA average winter (June-August) rainfall totals have decreased by approximately 20 % since the 1970s, while in Victoria the decreased rainfall trend occurred mostly from the mid-1990s, predominantly during late autumn and early winter (a decrease of approximately 20 % during the 1997-2010 period, relative to the historic average) (e.g. Murphy and Timbal, 2008;Hope et al, 2009;Verdon-Kidd and Kiem 2009a;Gallant et al, 2012). The decreased rainfalls in SWWA have been linked to a reduction in winter storm formation, with the growth rate of the leading storm track modes affecting southern Australia being more than 30 % lower during the period [1975][1976][1977][1978][1979][1980][1981][1982][1983][1984][1985][1986][1987][1988][1989][1990][1991][1992][1993][1994] compared to the period 1949-1968(Frederiksen et al, 2005.…”

“…For example, the Federation Drought (∼ 1895-1902) was associated with drought conditions covering the majority of the eastern two-thirds of Australia (Verdon-Kidd and Kiem, 2009a). From 1937 to 1945 Southeast Australia (SEA) was subjected to another multiyear drought, known as the World War II Drought, while more recently the Big Dry (or Millennium Drought) affected SEA during the mid-1990s through to early 2010 and resulted in a marked reduction in rainfall and runoff (NWC, 2006;Murphy and Timbal, 2008;Verdon-Kidd and Kiem, 2009a, b;Kiem and Verdon-Kidd, 2010;Gallant et al, 2012). In addition to the multi-year droughts mentioned, a number of shorter, equally intense droughts have also occurred during SEA's instrumental history (e.g.…”