Event Title

Determining Dominant Source Waters of Salmon River Tributaries Through ?D and ?180 Stable Isotope Anaysis

Presenter Information

Amanda Kern

Location

Eccles Conference Center

Event Website

http://water.usu.edu/

Start Date

4-20-2010 10:15 AM

End Date

4-20-2010 10:20 AM

Description

As the world's freshwater resources become increasingly scarce, an absolute understanding of the processes operating within the hydrologic cycle are vital for resource partitioning and conservation. Climate change researchers confirm increased temperatures over the past decade for much of the northern Rocky Mountain region and are concerned about continued temperature increases for the foreseeable future. Flowing through the northern Rocky Mountains, the Salmon River drains much of central Idaho with a watershed encompassing over 36,000 km2. Rising temperatures are predicted to alter the current flow regime of western rivers; escalating average winter temperatures will reduce the amount of annual snowpack by causing a phase change of average winter precipitation from snow to rain. Rising snowlines will alter the current flow pattern of Salmon River tributaries and consequently the Salmon River itself, modifying the timing and availability of water, affecting social, economic and biological systems operating within the Salmon River watershed. This project focuses on twelve Salmon River tributaries, utilizing stable isotope hydrology to define the dominant source of water maintaining discharge year round. The principal goal is to evaluate causes of regional contrasts between precipitation and river water ?D and ?180 compositions. Hydrogen and oxygen stable isotopes will be used as tracers to better understand the movement of water through the hydrologic system. Specifically, measurements of the isotopic composition of yearly precipitation will enable the identification of specific water masses and the tracing of their interrelationships. The hypothesis is that precipitation phase (rain/snow) in a single, small river basin provides a more powerful control on the isotopic composition at the outflow than internal fractionation processes. Twelve Salmon River tributaries have been sampled since May 2009 and will continued to be sampled through August 2010 for ?D and ?180 analysis. In addition to stream surface samples, precipitation will be sampled consistently throughout the term of study in an attempt to develop a local meteoric water line for the Salmon River watershed. We expect that our stable isotope analysis of collected precipitation and river water will help to define dominant source waters for chosen Salmon River tributaries. Predominant river source waters are expected to evolve through the year. During spring snowmelt all rivers are postulated to exhibit isotopic signatures homologous to that of regional snowfall because melt water from winter snow accumulation will be the number one contributing source to stream discharge. Conversely, in the later summer and early fall, snowmelt contributions are considered to be negligible and isotopic analysis should indicate a greater groundwater influence on stream flow. This broad hypothesis will be seen in varying degrees through the Salmon River watershed. Upper most elevation streams will, to some degree, have snowmelt contribution year round whereas lowest elevation streams may run dry before the end of the summer months. This project attempts to show that stream discharge is dependent upon precipitation input and is not greatly affected by watershed specific characteristics.

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Apr 20th, 10:15 AM Apr 20th, 10:20 AM

Determining Dominant Source Waters of Salmon River Tributaries Through ?D and ?180 Stable Isotope Anaysis

Eccles Conference Center

As the world's freshwater resources become increasingly scarce, an absolute understanding of the processes operating within the hydrologic cycle are vital for resource partitioning and conservation. Climate change researchers confirm increased temperatures over the past decade for much of the northern Rocky Mountain region and are concerned about continued temperature increases for the foreseeable future. Flowing through the northern Rocky Mountains, the Salmon River drains much of central Idaho with a watershed encompassing over 36,000 km2. Rising temperatures are predicted to alter the current flow regime of western rivers; escalating average winter temperatures will reduce the amount of annual snowpack by causing a phase change of average winter precipitation from snow to rain. Rising snowlines will alter the current flow pattern of Salmon River tributaries and consequently the Salmon River itself, modifying the timing and availability of water, affecting social, economic and biological systems operating within the Salmon River watershed. This project focuses on twelve Salmon River tributaries, utilizing stable isotope hydrology to define the dominant source of water maintaining discharge year round. The principal goal is to evaluate causes of regional contrasts between precipitation and river water ?D and ?180 compositions. Hydrogen and oxygen stable isotopes will be used as tracers to better understand the movement of water through the hydrologic system. Specifically, measurements of the isotopic composition of yearly precipitation will enable the identification of specific water masses and the tracing of their interrelationships. The hypothesis is that precipitation phase (rain/snow) in a single, small river basin provides a more powerful control on the isotopic composition at the outflow than internal fractionation processes. Twelve Salmon River tributaries have been sampled since May 2009 and will continued to be sampled through August 2010 for ?D and ?180 analysis. In addition to stream surface samples, precipitation will be sampled consistently throughout the term of study in an attempt to develop a local meteoric water line for the Salmon River watershed. We expect that our stable isotope analysis of collected precipitation and river water will help to define dominant source waters for chosen Salmon River tributaries. Predominant river source waters are expected to evolve through the year. During spring snowmelt all rivers are postulated to exhibit isotopic signatures homologous to that of regional snowfall because melt water from winter snow accumulation will be the number one contributing source to stream discharge. Conversely, in the later summer and early fall, snowmelt contributions are considered to be negligible and isotopic analysis should indicate a greater groundwater influence on stream flow. This broad hypothesis will be seen in varying degrees through the Salmon River watershed. Upper most elevation streams will, to some degree, have snowmelt contribution year round whereas lowest elevation streams may run dry before the end of the summer months. This project attempts to show that stream discharge is dependent upon precipitation input and is not greatly affected by watershed specific characteristics.

https://digitalcommons.usu.edu/runoff/2010/Posters/17