Memory of multi-year drought recorded in the deep root-zone

Multi-year droughts pose major challenges for water resource management because subsurface moisture and runoff recovery following drought remain difficult to predict. A key uncertainty is how precipitation is partitioned across the root-zone within deeply weathered landscapes. We directly measured shallow and deep root-zone moisture storage and compiled publicly-available groundwater and streamflow data over five water years (water years 2021 to 2025) in an oak–juniper woodland of central Texas spanning two years of exceptional drought followed by average precipitation. The upper 1.5 m showed depletion and near-recovery on storm-to-seasonal timescales, whereas depths from 1.5 to 5 m retained a persistent multi-year deficit that intensified during the second drought year due to deeper root-water uptake. Average precipitation in water year 2024 was largely partitioned to refill this deficit, impeding runoff generation. These results highlight the role of deep, root-driven, vadose zone moisture dynamics in mediating hydrologic recovery from multi-year droughts.