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ABSTRACT The Northeast United States exhibits significant spatial heterogeneity in flood seasonality, with spring snowmelt‐driven floods historically dominating northern areas, while other regions show more varied flood seasonality. While it is well documented that since 1996 there has been a marked increase in extreme precipitation across this region, the response of flood seasonality to these changes in extreme precipitation and the spatial distribution of these effects remain uncertain. Here we show that, historically, snowmelt‐dominated northern regions were relatively insensitive to changes in extreme precipitation. However, with climate warming, the dominance of snowmelt floods is decreasing and thus the extreme flood regimes in northern regions are increasingly susceptible to changes in extreme precipitation. While extreme precipitation increased everywhere in the Northeastern United States in 1996, it has since returned to near pre‐1996 levels in the coastal north while remaining elevated in the inland north. Thus, the inland north region has and continues to experience the greatest changes in extreme flooding seasonality, including a substantial rise in floods outside the historical spring flood season, particularly in smaller watersheds. Further analysis reveals that while early winter floods are increasingly common, the magnitude of cold season floods (Nov‐May) have remained unchanged over time. In contrast, warm season floods (June‐Oct), historically less significant, are now increasing in both frequency and magnitude in the inland north. Our results highlight that treating the entire Northeast as a uniform hydroclimatic region conceals significant regional variations in extreme discharge trends and, more generally, climate warming will likely increase the sensitivity of historically snowmelt dominated watersheds to extreme precipitation. Understanding this spatial variability in increased extreme precipitation and increased sensitivity to extreme precipitation is crucial for enhancing disaster preparedness and refining water management strategies in affected regions.
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This content will become publicly available on February 1, 2026
Watershed‐Scale Runoff Efficiency Response to Climate Variability
ABSTRACT The fraction of precipitation converted to stream discharge within a watershed, termed as runoff efficiency, may shift as climate changes. Runoff efficiency is known to be temperature‐sensitive in some watersheds, but temperature sensitivity is unquantified in many other watersheds. We identify regions where runoff efficiency is temperature‐sensitive using 942 watersheds, minimally influenced by anthropogenic activity, across the continental United States and Canada. Stepwise regression using historical discharge and climate records shows that runoff efficiency in 10 of 16 hydrologically similar hydro‐regions is sensitive to temperature, expanding the number of locations expected to experience temperature‐driven water stress, particularly in the North American continental interior. Runoff efficiency in all hydro‐regions demonstrates sensitivity to precipitation, but during wet years, runoff efficiency temporarily decreases, likely reflecting increasing groundwater storage. The temporary decrease in runoff efficiency is followed by an increase in the following year, likely due to the release of stored groundwater. This effect suggests changes in runoff efficiency help to stabilise watersheds, making it more difficult to both enter and leave drought as climate changes. The latter effect may partially explain observations of hydrologic drought persistence after meteorological drought ends. Understanding regional temperature sensitivity and the multiple‐year effect of precipitation will improve the ability to forecast runoff efficiency.
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- Award ID(s):
- 1951469
- PAR ID:
- 10608189
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Hydrological Processes
- Volume:
- 39
- Issue:
- 2
- ISSN:
- 0885-6087
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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