Causing of missing snowmelt following drought

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Dana Ariel Lapides , W Jesse Hahm, Daniella M Rempe, David N Dralle


Water management in snowy mountainous regions hinges on forecasting snowmelt runoff. However, droughts are altering snowpack-runoff relationships with ongoing debate about the driving mechanisms. For example, in 2021 in California, less than half of predicted streamflow arrived. Mechanisms proposed for this `missing' streamflow included changes in evapotranspiration, rainfall, and subsurface moisture conditions. Here, we demonstrate that evapotranspiration in drought years generates dry subsurface conditions that reduce runoff in subsequent years. A model including this legacy of depleted moisture storage reduced median error in 2021 forecasts from 60% to 20% at 15 minimally disturbed basins and from 18% to 2% at 6 water supply basins in the Sierra Nevada (basins range in area from 5-23,051 km2 and mean annual precipitation from 814-1549 mm. Our findings indicate that the relationship between snowpack and runoff will evolve as plant ecosystems respond to climate change and alter subsurface water storage dynamics.



Water Resource Management


Sierra Nevada, Forecasting, water resources, evapotranspiration, Snowpack


Published: 2022-03-05 16:21

Last Updated: 2022-07-18 22:50

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CC BY Attribution 4.0 International

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All data and code generated for this publication are available in published data repositories.

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