Techniques such as the Global Positioning System (GPS) and Gravity Recovery and Climate Experiment (GRACE) have been instrumental in tracking global freshwater resources, including groundwater. Despite their strengths, these methods have limitations. Dr. Christopher Ndehedehe, an ARC DECRA Fellow at Griffith's Australian Rivers Institute, noted, "GRACE provides reliable data at large and regional scales but struggles at local levels, while GPS data can be affected by technical and environmental factors including monument instability, thermal expansion of ground, and errors due to tidal aliases."

Both techniques also face challenges in accurately identifying short-term extreme events like sudden droughts. To address this, the research team combined GPS and GRACE vertical displacement data to develop a more effective approach for monitoring hydrological droughts.

This innovative method was tested in regions experiencing significant hydrological changes, such as the Amazon basin and California's Central Valley. "By combining GPS and GRACE data, the novel drought indicator enhances our ability to track short-term drought events more accurately, offering timely and actionable information for decision-makers," said Dr. Ndehedehe. He emphasized the importance of integrating climate change adaptation strategies with improved drought metrics for freshwater resource management.

While each technique performed well when compared to traditional drought indices like the standardized precipitation index, some extreme events went undetected. To improve detection, the team introduced the Multivariate Drought Severity Index, which merges GPS and GRACE data using advanced statistical methods. This allowed them to identify previously unrecognized drought events and their cascading effects on freshwater systems.

Dr. Artur Lenczuk, the lead author and Assistant Professor at the Military University of Technology in Poland, stated, "Droughts are complex, and their impacts can be devastating, particularly in regions with highly variable climatic conditions. Monitoring droughts is essential for effective water resource management."

The Multivariate Drought Severity Index demonstrated strong temporal consistency with both in-situ river discharge data and satellite-based agricultural indices, providing a comprehensive view of drought conditions and supporting improved global water management strategies.

As climate change continues to drive more frequent and severe droughts, monitoring shifts in climate and water storage becomes increasingly important for informed water resource management.

Research Report:A new Multivariate Drought Severity Index to identify short-term hydrological signals: case study of the Amazon River basin

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