Is society aware of “invisible” droughts? - a groundwater perspective

Climate change and anthropogenic activities increasingly stress groundwater resources, even in generally water-rich areas like Germany, threatening socio-economic and ecological systems. Since the impacts of groundwater droughts often emerge slowly and implicitly, it remains unclear to what extent they are noticed and recognized by society.

We address this gap by linking hydrological observations of groundwater droughts in Germany with news-derived indicators of societal awareness at the national scale. We analyzed 30-year groundwater records from and 521 regions and 13,900 monitoring wells across aquifers of different depths, after quality control including outlier screening, level-shift detection, and linear interpolation of short gaps (≤1 month) to daily resolution. We then identified drought periods and quantified their duration and severity using the variable threshold method, and classified events by the strength of potential human influence. Drought events with strong human influence are defined as those for which the variability of the associated time series dominates more by long-term trend rather than by interannual variability, or the event itself is strongly affected by abrupt level shifts. Finally, drought periods with strong and weak human influence were linked to a multi-sector drought-impact dataset derived from German newspaper articles (2000–2024) to assess societal awareness of groundwater droughts nationwide.

We found at least one drought event in 89.4% of the time series. In regions, drought events with weak human influence lasted, on average, 127 days and had a mean severity (maximum deviation below the drought threshold) of 0.2 m. Societal awareness was generally highest during the early phases of groundwater droughts, prior to the maximum groundwater-level deviation. Strong human influence amplified drought conditions, increasing the number of events by 7.2% and their mean duration by 2.9% within each region, and also leading to much earlier societal awareness. However, awareness did not persist throughout the drought period: awareness strength declined much faster than the groundwater-level recovery rate, and no significant relationship was found between changes in awareness strength and groundwater levels in deep aquifers during drought periods. These findings suggest that "invisible" groundwater droughts, especially in deep aquifers, are not fully perceived by society and highlight the need for improved groundwater policy coordination at the national level.