Climate change impacts on water availability in the Murrumbidgee River catchment

Climate change impacts on water availability in the Murrumbidgee River catchment

Global climate signature has been rapidly changing since mid-last century following modern industrialisation. The changing climate has impacted various natural systems and processes namely hydrological cycle, crop cycles and life cycles. Climate change impacts on the hydrological cycle are important aspects as human need water for domestic, agriculture and industrial use. Climate change impacts on water resources of the tropical and subtropical countries.

The effects of climate changes have been observed in the Murray-Darling Basin (MDB), which is one seventh of the total land area of Australia. This is the largest and most important agricultural production area in Australia. It produces more than $34 billion of agricultural products annually and accounts for about 46% of Australia’s total agricultural production. Since Australia’s economy largely depends on its natural resources, climate change impacts the economy in various ways.

According to the Intergovernmental Panel on Climate Change fifth assessment report (IPCC, AR5), the adaptive capacity and adaptation processes have increased in Australia. Australia has implemented policy and management changes in both rural and urban water systems to adapt to future drought, drier conditions and other climatic changes.

The main three rivers of the Murray Darling Basin, i.e. the River Murray, the Darling River and the Murrumbidgee River, capture most of the basin’s runoff. The objective of this study is to quantify future trend in water flows within the Murrumbidgee catchment under various climate scenarios. Better understanding of the impact of the climate change on river flows will assist in water resource planning in the MDB.

Future river flows have been estimated using the hydrological model, Simplified Hydrolog (SIMHYD), which is integrated with data from three different general climate models and emission scenarios. In this study, two different representative concentration pathway (RCP) emission scenarios RCP 4.5 and RCP 8.5 were selected to obtain downscaled future precipitation and potential evapotranspiration data from government agencies for the period of 2016 to 2100. Data from the two emission scenarios show an anticipated warmer and drier climate for the Murrumbidgee catchment. Runoff in the Murrumbidgee catchment is controlled by various dams and weirs, which yields positive results in runoff even when monthly rainfall trend was negative. The overall runoff simulations indicated that impact of climate change is short and intense.

The result of the Simplified Hydrolog (SIMHYD) modelling tool used in this study under RCP 4.5 scenario for the 2016 to 2045 period indicates a significant future impact from climate change on the volumes of runoff in the Murrumbidgee River catchment. The climate change prediction for the 2016 to 2045 period indicates a decrease in total annual rainfall by 9% to 19%. This reduction in rainfall translates to a 33% to 43% decrease in river runoff over the projected periods, although there is less confidence in the estimation of this prediction. This study shows potential runoff trends are higher in the downstream catchments (eastern part of Wagga Wagga), there can be opportunity to build irrigation dams for dry seasons irrigation.