Collaborative research: extreme 21ST century hydrologic volatility from the multimillennial perspective of giant sequoia

The National Science Foundation Division of Earth Sciences awarded Hydrologic Research Center $235,056 on August 1, 2026, under the Geosciences program (CFDA 47.050) to reconstruct three millennia of hydroclimatic variability in the Western United States using giant sequoia tree rings.

The project will update and expand a network of giant sequoia tree-ring chronologies across the Southern Sierra Nevada, combining dendrochronological data with hydrologic models to reconstruct snow water equivalent, soil moisture, precipitation, drought, and watershed-scale hydroclimate over the past 3,000 years. By placing recent drought and climate whiplash into a multimillennial context, the work will characterize the frequency, magnitude, and persistence of hydroclimatic extremes and develop new paleo-hydroclimatological methods to assess spatial and temporal variability at watershed scales. The project includes STEM workforce training and outreach to practitioners and the public.

Performance occurs in San Diego, California, with work proceeding through July 31, 2029.

Abstract

Western united states recently experienced an exceptionally long and severe drought punctuated by episodes of intense rainfall, producing rapid transitions from drought to deluge known as climate whiplash. These hydroclimatic extremes have profoundly affected water resources, ecosystems, agriculture, and economy, and are projected to become more frequent in the coming decades. Understanding whether these recent extremes are unprecedented or part of longer natural cycles is essential for planning a more resilient future. This project will use giant sequoia (sequoiadendron giganteum), one of the world's longest-lived and most iconic tree species, to reconstruct hydroclimatic variability over the past 3,000 years. By placing recent drought and climate whiplash into a multimillennial context, the project will improve understanding of the frequency, magnitude, and persistence of these hydroclimatic extremes. The project will include stem workforce training and outreach to practitioners and the public. This collaborative project will update and expand a network of giant sequoia tree-ring chronologies, which has not been comprehensively updated since 1995. Tree-ring chronologies from across the southern sierra nevada will be combined with state-of-the-art hydrologic models to reconstruct snow water equivalent, soil moisture, precipitation, drought, and watershed-scale hydroclimate over the past 3,000 years. The project will develop new paleo-hydroclimatological methods to characterize the spatial and temporal variability of hydroclimate at watershed scales, providing tools for investigating natural variability in snowpack, soil moisture, precipitation, and drought over millennial timescales. These reconstructions will place current and projected hydroclimatic variability within the full range of natural variability while improving probabilistic forecasts of hydroclimate across interannual to multidecadal timescales that account for both radiatively forced climate change and natural climate variability. The project will train students through a course-based undergraduate research experience. Educational impacts will be extended through an international dendrochronology summer course, an online training program, outreach to water managers and policymakers through a dedicated symposium session, and enhancement of a public giant sequoia exhibit. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the foundation's intellectual merit and broader impacts review criteria.- subawards are not planned for this award.