Summary
This study demonstrates that groundwater baseflow from deeper saturated zones plays a critical role in determining river flood magnitude across North American watersheds, often more so than soil moisture or short-term precipitation extremes. Analysis of 1981–2018 hydroclimatic records reveals that annual floods typically result from the co-occurrence of high precipitation and elevated baseflow, with flood magnitudes frequently more strongly related to antecedent baseflow variations. The findings suggest that multi-decadal flood trends align better with groundwater storage dynamics than with shifting precipitation patterns, highlighting the importance of considering deep water storage in flood prediction and climate adaptation.
Regional applicability
Whilst this study focuses on North American watersheds, the hydrological principles regarding groundwater contribution to flood risk are transferable to United Kingdom river systems, many of which similarly depend on baseflow from chalk and sandstone aquifers. UK flood forecasting and water resources management may benefit from greater emphasis on groundwater monitoring and long-term storage dynamics alongside precipitation-focused approaches.
Key measures
Annual flood magnitude, baseflow (groundwater-sustained river flow), antecedent baseflow, soil moisture, precipitation extremes, multi-decadal trends in flood magnitude and groundwater storage
Outcomes reported
The study analysed hydroclimatic records from thousands of North American watersheds (1981–2018) to quantify how groundwater baseflow affects annual flood magnitude at multiple timescales. The analysis revealed that flood magnitudes are often more strongly correlated with antecedent baseflow than with soil moisture or short-term extreme precipitation.
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