A ‘global-scale’ study of groundwater levels by a team of researchers from the University of California at Santa Barbara (UCSB), ETH Zürich, University College London (UCL), Rutgers University and King Abdulaziz University was published on 24 January 2024 in Nature. The analysis is rooted in the analysis of millions of groundwater-level measurements in 170,000 wells from 1,693 aquifer systems in over 40 countries. Part of the data used for this study is now available in IGRAC’s Global Groundwater Information System (GGIS).
New compilation of groundwater levels monitoring data
Led by Scott Jasechko (UCSB), Debra Perrone (UCSB) and Hansjörg Seybold (ETH Zürich), the team spent years compiling and curating the dataset that led ultimately to the analysis of time series records (for at least 8 years) in 170,000 monitoring wells. For about 50% of these data, the responsible authorities, data owners or data providers have given approval to share them on the GGIS. In this dedicated viewer, users can browse over regions of interest, visualise the trend indicators calculated at the monitoring stations’ and aquifer systems’ levels, and consult the monitoring data charts.
The dataset of Jasechko et al. (2024) combines data from a variety of sources, ranging from official groundwater monitoring networks to research studies. In comparison, the Global Groundwater Monitoring Network (GGMN), as a UN-supported programme, exclusively contains data collected and publicly shared by the countries.
Rapid groundwater-level declines
The article, Rapid groundwater decline and some cases of recovery in aquifers globally, confirms that groundwater-level declines are widespread in the twenty-first century, especially in dry regions with extensive croplands. Here, in regional aquifers underlying Iran, India, Spain, United States, Saudi Arabia, Morocco and Mexico median rates of groundwater-level decline exceed a metre per year.
Worryingly, the study reveals an acceleration in rates of groundwater-level decline over the past four decades in 30% of the world’s regional aquifers. The analysis also notes that twenty-first century precipitation rates were lower than in the late twentieth century for most aquifer systems that exhibit an acceleration in groundwater-level declines. This could indicate a potential link between decadal-scale climate variability and climate change in accelerating groundwater-level declines either from reduced rates of groundwater recharge or increased water demand for irrigation. This widespread acceleration in groundwater-level declines highlights an urgent need for more effective measures to address groundwater depletion.
Successful human interventions
Jasechko et al. (2024) also highlight some successful human interventions addressing groundwater depletion. For example, in Bangkok (Thailand), groundwater-level declines of the 1980s and 1990s were reversed following the implementation of regulations designed to reduce groundwater pumping. Meanwhile, in Albuquerque, New Mexico (USA), groundwater levels are recovering after an inter-basin transfer of surface water alleviated groundwater demand. And finally, a managed aquifer recharge scheme in the Avra Valley of Arizona (USA) is replenishing a depleted aquifer using water that has been diverted from the Colorado River.
Crucial importance of in-situ monitoring data
Similar to IGRAC’s contribution to the State of Global Water Resources report and previous studies before, this study demonstrates the relevance of groundwater monitoring data to inform on the state of groundwater resources, not only at the local or national scale, but also on a global scale.