Climate changes and variability in the Great Artesian Basin (Australia), future projections, and implications for groundwater management

The Great Artesian Basin (GAB) in Australia is one of the largest aquifer systems in the world and it supports a range of agriculture, industry, fragile ecosystems, and townships. Climate variability and future projections of climate change will impact on both recharge of the GAB and demands on the resource. Understanding the climate in the GAB region is therefore critical to informing regional groundwater management. Observed decadal climatic variability and trends were assessed for significance with Kendall's test and investigated in light of future climate scenarios with 40 global climate model (GCM) outputs. Historic climate observations show that the GAB region had become warmer and wetter over the last five to six decades. The annual rainfall increased by 0.95 mm/year(2) during the period 1960-2016, although this trend magnitude was neither statistically significant nor uniform geographically across the GAB. The annual means of daily mean, maximum, and minimum temperatures increased during that period by 0.019, 0.019, and 0.020 degrees C/year, with statistically significant increases in 92.4, 91.4 and 85.1% of the GAB, respectively. Trends of other rainfall statistics associated with recharge indicated an increase of the 95th percentile daily rainfall amount, an increase of average rainfall intensity, and a statistically significant decrease in mean wet-spell length. In contrast with past warm and wet climate, the future climate in the GAB region is projected to be warmer and drier, which would potentially produce serious challenges for groundwater resources management for the region.