Drought Over Time: an Investigation of the Impact of Meteorological Drought on Groundwater and Surface Water in the East of Romania

Abstract Drought stands out among natural hazards due to its multi-faceted character and cumulative effects. Its far-reaching impact is expected to cause even greater concern in the context of climate change, calling for improved water management strategies grounded in scientific knowledge. This study aims to take an in-depth look at the impact of meteorological drought on underground and surface water resources, taking the eastern region of Romania as a case study. The multi-temporal assessment was performed through correlative analyses between the Standardized Precipitation Evapotranspiration Index (SPEI) computed for 1, 3, 6, 9, and 12 months and (i) the mean monthly groundwater level, (ii) the mean monthly river discharge, and (iii) the minimum monthly river discharge. The three sets of analyses result in negative statistically significant correlations between the SPEI and the groundwater level, and positive statistically significant correlations between the SPEI and the river discharge. The strongest correlations (0.4–0.6) are obtained by integrating delays of 6 (mainly 0.25–0.4, p < 0.05), 9 (mainly 0.25–0.4, p < 0.05), and 12 (mainly 0.25–0.4, with certain values over 0.6, p < 0.05) months between the above-mentioned hydro-climatic parameters. All correlations decrease in strength following a North-South direction, which shows the influence of the local hydro-climatic setting. Such findings can support the prognosis of water availability, which is critical in the eastern part of Europe, given its proneness to frequent, high-intensity meteorological droughts. This study contributes to our understanding of the impact of meteorological drought on both underground and surface water, adding to the growing literature that integrates these aspects. Graphical Abstract The aim of this study is to investigate the impact of meteorological drought on groundwater and surface water resources. A three-step methodological workflow was developed to explore this impact, taking the northeastern region of Romania as a case study. The multi-temporal assessment was performed through correlative analyses between the Standardized Precipitation Evapotranspiration Index (SPEI) computed for 1, 3, 6, 9, and 12 months and (i) the mean monthly groundwater level, (ii) the mean monthly river discharge, and (iii) the minimum monthly river discharge. Our analysis showed that SPEI values negatively correlate with the mean monthly groundwater level, and positively correlate with the mean monthly and minimum monthly river discharge. Another key result is that the strongest correlations occur with 6-, 9-, and 12-month delay. Correlation strength declines from North to South, reflecting local ginfluences. Such findings can support the prognosis of water availability, which is critical in the eastern part of Europe, given its proneness to frequent, high-intensity meteorological droughts. Authorities can use these results to guide local-level water management and inform decision-making for socio-economic development.