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- Title
The Roles of Winter Versus Summer Precipitation in Supplying Evapotranspiration Across US Ecoregions: A Cross‐Catchment End‐Member‐Splitting Analysis.
- Authors
Kesting, Helen M.; Allen, Scott T.
- Abstract
Understanding how changing seasonal precipitation will affect ecosystems and water resources can benefit from understanding how precipitation from different seasons contributes to runoff versus evapotranspiration (ET). We use stable‐isotope data from 23 National Ecological Observatory Network watersheds to quantify the fractions of winter and summer precipitation that supply ET, and the fractions of ET supplied by summer versus winter precipitation. Across 20 watersheds, 34%–101% of summer precipitation supplied ET, with 8%–105% of ET supplied by summer precipitation; these end‐member‐splitting solutions were poorly constrained in the other three watersheds. These precipitation partitioning fractions were significantly correlated with many topographic, climatic, and vegetation metrics. This first empirical study of seasonal precipitation partitioning fractions across diverse ecoregions demonstrates that they can be well‐constrained in many locations using existing public data sets, and that partitioning‐fraction variations are largely explained by climate variations. Plain Language Summary: While it is well known that plant water use and soil evaporation mostly occur in summer, little is known about the source of the precipitation that supplies those fluxes. For example, little is known about whether summer rain is more likely to be returned to the atmosphere versus contributing to streamflow. We have applied a recently developed method using naturally occurring chemical signals in precipitation to answer such questions across data sets from 23 watersheds spanning the US. Across these sites, we identified a wide range of behaviors, including plant water use and soil evaporation ranging from being entirely supplied by summer precipitation to entirely supplied by winter precipitation. That involved patterns ranging from all of summer precipitation becoming evapotranspired to a small fraction of it being evapotranspired. This new exploratory analysis provides a first field‐data‐based set of insights into questions that have been otherwise the domain of simulation models, providing a new view of how precipitation is partitioned between streamflow and evapotranspiration across the US. Key Points: End‐member mixing and splitting can yield well‐constrained quantifications of evapotranspiration (ET) sources and seasonal precipitation fates from National Ecological Observatory Network dataOn average, most summer precipitation was used by ET but ET was equally supplied by winter and summer precipitationThese precipitation partitioning fractions were strongly correlated with various climate and vegetation metrics
- Subjects
CLIMATE change; EVAPOTRANSPIRATION; SUMMER; PLANT-water relationships; PRECIPITATION (Chemistry); WATERSHEDS; WINTER storms; WINTER
- Publication
Geophysical Research Letters, 2024, Vol 51, Issue 12, p1
- ISSN
0094-8276
- Publication type
Article
- DOI
10.1029/2024GL109112