Evidence of impacts from rising temperature on inflows to the Murray‐Darling Basin

Abstract

The 2001–2007 Australian drought was the hottest on record with inflows to Australia's longest river system, the Murray‐Darling, reaching an historical low. Here we examine the relative importance of rising temperature and decreasing rainfall over its catchment, the Murray Darling Basin (MDB). Although annual‐total inflow is more sensitive to rainfall over the southern MDB, where rainfall since 2001, has been the lowest on record, this alone can not explain the observed inflow decline. A relationship exists between inflow variations and fluctuations of temperature not associated with rainfall in the austral winter and spring: a rise of 1°C leads to an approximate 15% reduction in the climatological annual inflow. Our results provide strong evidence that rising temperatures due to the enhanced greenhouse effect have a strong impact on southern Australia's water resources, in addition to any reduction in rainfall, and project a long‐term decline in inflows to this river system as the greenhouse effect continues.

What causes southeast Australia's worst droughts?

“…This period is characterized by severe drought conditions, with the largest negative PDSI value of the 20th Century, close to À4 (Figure 1d). These low-rainfall years are exacerbated by anomalously warm temperatures of 0.3-0.6°C above the long-term average (Figure 1c) [Cai and Cowan, 2008a], contributing to the severity of the drought via increased potential evaporation [Nicholls, 2004].…”

Streamflow decline in southwestern Australia, 1950–2008

“…[Cai and Cowan, 2008] have argued that runoff decline in SEA is related not only to declining rainfall but also to increasing temperature that presumably increases evaporation. However, [Donohue et al, 2010] showed that, despite increasing air temperatures, changes in vapour pressure, net radiation and wind speed result in declining PE for much of Australia.…”

Australia's Murray - Darling Basin: freshwater ecosystem conservation options in an era of climate change

“…Increased evapotranspiration as a result of increased air temperatures, more interception structures and land use have dramatically reduced runoff (van Dijk et al 2006;Timbal and Jones 2008;MDBA 2009a). In the MDB, a 15% reduction of inflows has been observed for a 18C rise in average temperature; a 28C temperature rise by 2060 could result in a 55% reduction in inflows from reduced precipitation and increased evapotranspiration (Cai and Cowan 2008).…”