Fresh water quenches our thirst, is used to grow our food, and sustains our rivers, springs, and wetlands, as well as the ecosystems they support. You may not think about it, but most of the world’s fresh water, 98% in fact, is stored out of sight, and out of mind. That is, most of the world’s fresh water is stored underground. Groundwater plays many important roles.
While future rainfall is notoriously difficult to project, most models suggest more extreme weather events, shifting temperatures and changing rainfall patterns, which all affect the availability of surface water resources, and increasing reliance on groundwater resources.
Increased groundwater extraction – at what cost?
Increased groundwater extraction can lead to declining water tables, damage to groundwater dependent vegetation and land subsidence which can lead to irreversible reduction in the volumes of water that can be stored underground. As parts of the world get hotter and drier, and with pressures to increase agricultural outputs, the demands placed upon groundwater are expected to increase.
A deeper look at recharge rates
Understanding groundwater recharge, the rain that replenishes underground water systems, is vital for the management of both surface water and groundwater resources. Despite its importance, quantifying recharge rates is surprisingly difficult. Methods to estimate recharge are typically based on measurements of changes in water levels or based on water chemistry.
Recent research led by Charles Darwin University, produced an AI-based recharge model for the entire Australian continent. Their work used almost 200,000 measurements of groundwater chloride, collated from measurements collected by hundreds of scientists, over a 60-year timeframe.
Their resulting recharge dataset, by far the largest ever produced anywhere in the world, produces a detailed assessment about the variability in recharge rates across Australia. From less than 1 mm/y, to over 1 m/y, their estimates show the huge variability in groundwater recharge rates across Australia. The resulting model produced across the entire continent produces baseline recharge estimates, even in regions without other field-based estimates of recharge, providing much needed information to inform water resources management.
Dylan Irvine explains: “Previous large-scale collations of recharge estimates have used results obtained from many different methods. Each method has vastly different assumptions and can produce widely varying estimates.
“The application of a single technique, the most widely used technique in Australia – on a massive dataset – are the strength of this work.”
“This paper is our best efforts to utilise datasets collected over many decades, often from before any of the paper’s authors were even born.”
“Effective water resource management ensures flowing rivers, healthy vegetation, and access to water for irrigation. Any information that can assist effective water resources management is thus vital.”
Outputs from the model and the method used to estimate recharge are available at the following link:
https://hess.copernicus.org/articles/28/1771/2024/https://www.hydroshare.org/resource/5e7b8bfcc1514680902f8ff43cc254b8/