Abstract

In 2008, the U.S. Geological Survey Global Change Program funded a study to examine integrated watershed scale response to global change in selected watersheds across the United States. Fourteen watersheds for which hydrologic models had been created using the Precipitation Runoff Modeling System (PRMS) were selected as study sites. PRMS is a deterministic, distributed-parameter, watershed model developed to evaluate the effects of various combinations of precipitation, temperature, and land use on streamflow and hydrology. The portion of the South Fork Flathead River watershed located upstream from Hungry Horse Dam in northwestern Montana is 1 of the 14 study sites.

Results from six General Circulation Models (GCMs), each using three GCM scenarios, were used to develop climate change scenarios for 2001-2099 for input to the existing PRMS model for the South Fork Flathead River. These PRMS simulations using the GCM scenarios were compared to PRMS simulations for current (1988-2000) conditions. All GCM simulations project an overall increase in temperature. Projected changes in precipitation for the South Fork Flathead River watershed were variable, with a slight tendency towards an increase in precipitation in the latter half of the 21st century.

PRMS simulations using the GCM scenarios project slightly increased mean annual streamflow in the South Fork Flathead River from about 2020-2099. However, these simulations project that less precipitation falls as snow, resulting in increased mean monthly streamflow January through April and decreased mean monthly streamflow June through September. Information from these climate-change simulations could be useful for management of Hungry Horse Reservoir.

Start Date

5-3-2010 2:00 PM

End Date

5-3-2010 2:30 PM

Document Type

Presentation

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Mar 5th, 2:00 PM Mar 5th, 2:30 PM

Watershed Scale Response to Climate Change— South Fork Flathead River, Montana

In 2008, the U.S. Geological Survey Global Change Program funded a study to examine integrated watershed scale response to global change in selected watersheds across the United States. Fourteen watersheds for which hydrologic models had been created using the Precipitation Runoff Modeling System (PRMS) were selected as study sites. PRMS is a deterministic, distributed-parameter, watershed model developed to evaluate the effects of various combinations of precipitation, temperature, and land use on streamflow and hydrology. The portion of the South Fork Flathead River watershed located upstream from Hungry Horse Dam in northwestern Montana is 1 of the 14 study sites.

Results from six General Circulation Models (GCMs), each using three GCM scenarios, were used to develop climate change scenarios for 2001-2099 for input to the existing PRMS model for the South Fork Flathead River. These PRMS simulations using the GCM scenarios were compared to PRMS simulations for current (1988-2000) conditions. All GCM simulations project an overall increase in temperature. Projected changes in precipitation for the South Fork Flathead River watershed were variable, with a slight tendency towards an increase in precipitation in the latter half of the 21st century.

PRMS simulations using the GCM scenarios project slightly increased mean annual streamflow in the South Fork Flathead River from about 2020-2099. However, these simulations project that less precipitation falls as snow, resulting in increased mean monthly streamflow January through April and decreased mean monthly streamflow June through September. Information from these climate-change simulations could be useful for management of Hungry Horse Reservoir.