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

摘要

In 2008, the U.S. Geological Survey Global Change Science Program supported a study to examine watershed-scale response to global change in selected watersheds across the United States. As part of this study, output from six General Circulation Models (GCMs), each using four GCM scenarios, were used to develop an ensemble of climate-change scenarios for 2001-2099 for input to the existing Precipitation-Runoff Modeling System (PRMS) model for the South Fork Flathead River in northwestern Montana. All GCM scenarios project an overall increase in temperature and a tendency towards an increase in precipitation in the latter half of the 21st century for the South Fork Flathead River Basin. PRMS simulations using downscaled GCM scenarios predict slightly increased mean annual streamflow in the South Fork Flathead River by 2099. Mean monthly streamflow is predicted to increase November through April (snow season) and decrease May through July (snowmelt season and early part of the low-flow season). These simulations did not consider land-cover dynamics, such as changes in the watershed due to forest fires. Information from these PRMS simulations using downscaled GCM scenarios may be useful for long-term management of Hungry Horse Reservoir.