Integrating Historical, Proxy, and Documentary Evidence for a Multi-centennial Drought Reconstruction for the Greater Dublin Area, Ireland

Resilient water-resources planning needs long datasets that capture low-frequency variability and rare, high-impact events beyond the instrumental era. This is particularly important in the Greater Dublin Area (GDA), where increasing water demand and reliance on a small number of linked sources and ageing infrastructure increases exposure to prolonged rainfall deficits. With major investment planned for new supplies and transfers, drought risk should be assessed against a long baseline. Here we develop a multi-method, multi-source reconstruction that extends monthly precipitation totals for the GDA back to 1748, and summer (MJJA) precipitation back to 1200.

Observations for the GDA are derived from the newly developed long-term gridded rainfall product produced by Met Éireann, the national meteorological agency. This extended gridded dataset integrates observations recovered through various citizen science and data rescue initiatives. For the GDA, we further extend monthly precipitation back to 1748 using two complementary approaches. First, we apply statistical reconstruction using physically interpretable circulation and hydroclimate predictors, including long sea-level pressure (SLP) series, pressure-gradient indices, and teleconnection modes. Models are calibrated separately for each calendar month using Lasso regression and random forests and uncertainties estimated using bootstrap resampling. Second, we scale monthly and annual precipitation anomalies for the period 1711-1977 compiled in a UK Met Office Branch Memorandum (No. 77) by Jenkinson et al. (1979) to observed GDA precipitation. This unpublished series combines early instrumental observations with documentary weather diaries (quantified via a graded wet–dry ranking scheme), drawing on UK regional series when Irish data are sparse and increasingly using Irish station records from the late 18th century onwards. Drought events identified from the reconstructed rainfall series are further verified using documentary sources, including the Irish Drought Impacts Database (1733-2019) derived from newspaper records, linking meteorological drought to locally reported impacts. 

Finally, to extend the series further back, UK-based tree-ring records (oak cellulose δ¹⁸O) are used to reconstruct MJJA precipitation back to 1200. These data from central England are calibrated to the GDA using variance scaling and assessed with split-period verification. Together, these evidence streams provide a basis for a multi-centennial precipitation series and drought catalogue for the GDA, suitable for water-resources assessment and planning.