Event Title

Multi-centennial length stream flow reconstructions for the Bear River reveal substantial pre-settlement variability

Location

Eccles Conference Center

Event Website

http://water.usu.edu

Start Date

4-1-2014 2:20 PM

End Date

4-1-2014 2:40 PM

Description

The Bear River is the single-most important contributor of stream flow to the closed-basin Great Salt Lake, and represents the only future potential for additional storage capacity (i.e., water development) in northern Utah and the Wasatch front. Originating in the western Uinta Mountains of Utah, the Bear River flows into Wyoming, back into Utah, then Wyoming again, before crossing into southeastern Idaho and entering Utah one last time before terminating in the right arm of the Great Salt Lake. Not surprisingly, water management during the settlement period on the Bear is complex and diversions and flow-through not readily quantified or monitored. Despite the Bear River’s importance for rural, urban, and wildlife (Bear River Migratory Refuge) water delivery, we lack sufficient understanding outside the historical record of the potential variability in stream flow for this River. As part of a larger effort to understand regional hydroclimatic variability, the Wasatch Dendroclimatology Research Group has undertaken a massive effort to collect paleoclimate proxies (i.e., tree rings) that characterize precipitation and stream flow. Over two-dozen tree-ring chronologies were screened as predictors of Bear River stream flow for two gages the Utah-Wyoming border, and Smith’s Fork. These gages were selected based on their length and relatively unaltered flow regimes. Preliminary regression models explained over 60% of the variability in historical stream flows, and resulting reconstructions extended ~600 and ~400 years for Utah-Wyoming and Smith’s Fork, respectively. While the gages were separated by only ~60 km there were substantial high-frequency differences in the flow regimes over the past 400 years. Conversely, as expected there were strong similarities in low-frequency variability that likely reflected the region’s dominant weather patterns, which deliver the majority of precipitation from the west during the winter. While the 1930s drought (1936) and the early 2000s drought (2004) served as the drought-of-record for Bear Lake, (downstream from both gages) there were multiple instances of longer and more intense droughts in the paleoclimate record. The longer record provides additional insight for water management planning, and may help to portend future water shortages. Comparison of Bear River stream flow to recent reconstructions of the Logan River, Weber River, and the Great Salt Lake level provided a larger context for intra-regional precipitation variability. While low-frequency patterns appeared coherent, there were important differences in year-to-year variability across a latitudinal gradient, which we hypothesized were, at least in part, driven by an intransient teleconnection to the central Pacific (i.e., El Nino-Southern Oscillation). Additionally, overall similarity in mutli-decadal variability among the reconstruction data sets was correlated to climate forcing from the north Pacific.

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Apr 1st, 2:20 PM Apr 1st, 2:40 PM

Multi-centennial length stream flow reconstructions for the Bear River reveal substantial pre-settlement variability

Eccles Conference Center

The Bear River is the single-most important contributor of stream flow to the closed-basin Great Salt Lake, and represents the only future potential for additional storage capacity (i.e., water development) in northern Utah and the Wasatch front. Originating in the western Uinta Mountains of Utah, the Bear River flows into Wyoming, back into Utah, then Wyoming again, before crossing into southeastern Idaho and entering Utah one last time before terminating in the right arm of the Great Salt Lake. Not surprisingly, water management during the settlement period on the Bear is complex and diversions and flow-through not readily quantified or monitored. Despite the Bear River’s importance for rural, urban, and wildlife (Bear River Migratory Refuge) water delivery, we lack sufficient understanding outside the historical record of the potential variability in stream flow for this River. As part of a larger effort to understand regional hydroclimatic variability, the Wasatch Dendroclimatology Research Group has undertaken a massive effort to collect paleoclimate proxies (i.e., tree rings) that characterize precipitation and stream flow. Over two-dozen tree-ring chronologies were screened as predictors of Bear River stream flow for two gages the Utah-Wyoming border, and Smith’s Fork. These gages were selected based on their length and relatively unaltered flow regimes. Preliminary regression models explained over 60% of the variability in historical stream flows, and resulting reconstructions extended ~600 and ~400 years for Utah-Wyoming and Smith’s Fork, respectively. While the gages were separated by only ~60 km there were substantial high-frequency differences in the flow regimes over the past 400 years. Conversely, as expected there were strong similarities in low-frequency variability that likely reflected the region’s dominant weather patterns, which deliver the majority of precipitation from the west during the winter. While the 1930s drought (1936) and the early 2000s drought (2004) served as the drought-of-record for Bear Lake, (downstream from both gages) there were multiple instances of longer and more intense droughts in the paleoclimate record. The longer record provides additional insight for water management planning, and may help to portend future water shortages. Comparison of Bear River stream flow to recent reconstructions of the Logan River, Weber River, and the Great Salt Lake level provided a larger context for intra-regional precipitation variability. While low-frequency patterns appeared coherent, there were important differences in year-to-year variability across a latitudinal gradient, which we hypothesized were, at least in part, driven by an intransient teleconnection to the central Pacific (i.e., El Nino-Southern Oscillation). Additionally, overall similarity in mutli-decadal variability among the reconstruction data sets was correlated to climate forcing from the north Pacific.

https://digitalcommons.usu.edu/runoff/2014/2014Abstracts/13