Snow-fed streamflow timing at different basin scales: Case study of the Tuolumne River above Hetch Hetchy, Yosemite, California

Water Resources Research
By: , and 

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Abstract

Diurnal cycles in snow‐fed streams provide a useful technique for measuring the time it takes water to travel from the top of the snowpack, where snowmelt typically peaks in the afternoon, to the river gauge, where the daily maximum flows may arrive many hours later. Hourly stage measurements in nested subbasins (6‐775 km2) of the Tuolumne River in Yosemite National Park illustrate travel time delays at different basin scales during the spring 2002 and 2003 melt seasons. Travel times increase with longer percolation times through deeper snowpacks, increase with longer travel times over land and along longer stream channels, and increase with slower in‐stream flow velocities. In basins smaller than 30 km2, travel times through the snowpack dominate streamflow timing. In particular, daily peak flows shift to earlier in the day as snowpacks thin and mean discharges increase. In basins larger than 200 km2, snowpack heterogeneity causes the hour of peak flow to be highly consistent, with little or no variation as the snowpack thins. Basins with areas in between 30 and 200 km2 exhibit different sequences of diurnal streamflow timing in different years, sometimes acting like small basins and other times like large basins. From the start of the melt season until the day of peak snowmelt discharge, increasing travel distances in channels as the snow line retreats to higher elevations do not cause long enough travel delays to offset the observed decrease in mean travel times through the snowpack. A model that couples porous medium flow through thinning snowpacks with free surface flow in stream channels can reproduce the observed patterns, provided that the model incorporates snowpack heterogeneity.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Snow-fed streamflow timing at different basin scales: Case study of the Tuolumne River above Hetch Hetchy, Yosemite, California
Series title Water Resources Research
DOI 10.1029/2004WR003933
Volume 41
Issue 7
Year Published 2005
Language English
Publisher AGU
Contributing office(s) Pacific Regional Director's Office, San Francisco Bay-Delta, Toxic Substances Hydrology Program
Description 14 p.
First page 1
Last page 14
Country United States
State California
Other Geospatial Yosemite National Park
Online Only (Y/N) N
Additional Online Files (Y/N) N