A wealth of groundwater level data is collected across Australia. Across each state and territory, water level data is collected for tens of thousands of bores, sent to the Bureau and published in the Australian Groundwater Explorer. The Bureau has been able to integrate this data with contextual information on climate change, groundwater extraction, rainfall and streamflow to provide insight in those factors impacting groundwater levels across Australia.
Methodology and Results
The Bureau produces estimates of groundwater level trend and status for bores across the nation, where status is defined as a decile rank of current levels. However, groundwater data is notoriously variable, typically having sporadic temporal frequency, highly variable lengths of record, and limited quality control of the historical record. This makes it difficult to sensibly apply a trend method across all groundwater systems in Australia.
Current methods used to estimate trends and status were designed to be applicable to the widest set of bores, thus giving the broadest coverage across Australia. These methods use monthly average groundwater levels to estimate trends and annual average groundwater levels to estimate status. While this approach captures broad trends very well, it can produce undesirable results in some bores, especially where seasonal fluctuations are much greater than long term trend. To address this, the Bureau has developed a methodology which focuses on assessing the trends and status based only on annual recovery peaks. This method automatically identifies recovery peaks during the non-pumping season, and assesses trends and status based on the recent peak against peaks in prior years. However, this method is restrictive in its application as it requires a higher frequency of water level readings for each bore analysed.
By assessing trends and status based only on annual recovery peaks the trends and status are improved, better representing the recovery of the aquifer rather than average values across the year. These improved trends can provide quick, yet accurate, insights into changes in groundwater resources across Australia. An example of how this has been used to asses the impact of drought in the Murray Darling Basin will be presented. This approach delivers an improved visualisation of changes in groundwater resources across Australia.