Despite the impact Australia’s extreme climate has on water resources, bushfire management and food production the way Total Water Storage (TWS) across Australia changes and evolves in response to “droughts and flooding rains” remains unknown. Using data derived from satellites a UTS led team has, for the first time, investigated the consequences a decade long drought, followed by a dramatic increase in rainfall, has on Australia’s water storage dynamics.
The results, published in Remote Sensing of Environment showed that Australia gained 3 times more water during the ‘big wet’ of 2010 - 2011 than was lost in the ‘big dry’, one of Australia’s worst droughts that lasted from 2001 – 2009.
The unique aspect of the GRACE twin satellites, meant the researchers could measure the extent and magnitude of “groundwater resource”s and detect “hidden droughts” such as the depletion of groundwater, which is currently very difficult to monitor.
Lead author, PhD candidate Zunyi Xie from the UTS Plant Functional Biology and Climate Change Cluster (C3) said that an accurate evaluation of how water is used in the landscape under extreme climatic events, such as droughts and floods, was of great importance for better managing water resources.
“This is particularly so for Australia, one of the driest continents on earth. Climate change is predicted to increase climate variability so this study will not only guide the design of Australia’s national water-use strategies to a changing climate, but will also generate key knowledge for understanding the water-cycle dynamics at a global scale.”
The research team used data derived from the Gravity Recovery and Climate Experiments (GRACE) satellites to study Australia’s water storage dynamics from 2002 to 2014.
“Previous studies have concentrated on the causes of these extreme events and the impacts on agriculture and ecosystems, treating the big dry and big wet as discrete periods over the entire continent. This isn’t very realistic given the diversity of Australia’s climate patterns, “ Xie says.
To better characterise temporal variations of TWS across the continent, the scientists developed a new method to define a per-pixel transition date between dry and wet periods based on GRACE observations. Using this method the ‘big dry’ and ‘big wet’ periods were independently derived for each pixel.
“We found the timing of the transition date between the ‘big dry’ and ‘big wet’ varied considerably across the continent. Overall, there was a 12 month lag in the hydroclimatic shift from ‘big dry’ to ‘big wet’ conditions between eastern and western parts of Australia”.
Xie said that the study demonstrates that a simplified classification of a single, continent-wide transition date between ‘big dry’ and ‘big wet’ is unrealistic and unable to provide accurate information about the hydrological dynamics over the continent
“We found highly variable continental patterns in water resources, involving differences in the direction, magnitude, and duration of total water storage responses to drought and wet periods. These responses clustered into three distinct geographic zones that correlated well with the influences from multiple large-scale climate modes,” Xie said.
The team, which also included Dr Graziella Caprarelli from the University of South Australia believe the use of remote sensing technology in this way will eventually allow water resource managers to monitor groundwater status and optimize multiple-use water pumping allocations for crops, groundwater-dependent ecosystems, wetlands, and urban drinking supplies.
“Similarly, when ground water depths are shallow, the GRACE satellite measures can forewarn of pending flood risks,” Xie says
Professor Alfredo Huete, co-author and Team Leader of the C3 Ecosystem Dynamics Health and Resilience research program said the results highlight the value of GRACE derived data as an important indicator of hydrological system performance for improved water impact assessments and management of water resources across space and time.
Funding:
The research was supported by UTS, Chinese Scholarship Council and the Australian Research Council Discovery Project “Impact of extreme hydro-meterological conditions on ecosystem functioning and productivity patterns across Australia”.
Publication details:
Spatial partitioning and temporal evolution of Australia's total water storage under extreme hydroclimatic impacts Zunyi Xie, Alfredo Huete, Natalia Restrepo-Coupe, Xuanlong Ma Rakhesh Devadas, Graziella Caprarelli
Remote Sensing of Environment Vol 183, September 2016, pages 43 - 52 doi:10.1016/j.rse.2016.05.017