Hydrometeorological and hydrogeological trends and drought dynamics in a cold-humid, coastal region

Quantifying groundwater response to droughts remains challenging, as aquifers typically respond to meteorological conditions with delays, and long-term groundwater records remain limited. This study investigated statistical relationships among meteorological, hydrogeological, and hydrological datasets in the Canadian province of Nova Scotia. Standardized Groundwater Index (SGI) values were calculated using daily groundwater level data (2009–2025) from 32 observation wells and compared with meteorological (Standardized Precipitation Evapotranspiration Index, SPEI) and hydrological (Standardized Base Flow Index, SBFI) drought indicators. To complement the statistical analyses of drought dynamics, geospatial drought layers were used to examine spatiotemporal patterns in drought severity and distribution. In most groundwater systems, SGI exhibited short (< 1 month) lag times and strong correlations (> 0.5 on average) with both SPEI and SBFI, suggesting the atmosphere-aquifer-stream hydrologic continuum patterns are strongly associated. Trend analysis revealed that the fall season is experiencing the most significant and persistent negative trends across the hydrological cycle (net precipitation, baseflow, and groundwater level). Significant negative fall trends were identified in 67% of net precipitation records, 60% of streamflow records, 40% of baseflow records, and 25% of groundwater level records. Kernel density analyses for summer and fall indicated significant shifts toward drier SPEI, SGI, and SBFI distributions (p < 0.05) after 2016. The geospatial drought layer analysis reveals that more intensive droughts are becoming more frequent and spatially extensive. Collectively, the results yield a better understanding of drought characteristics in a cold, coastal region, an essential step towards evaluating ongoing climate change impacts in similar environments worldwide.