Assessment of hydrological uncertainty in a changing climate in the Pacific Northwest River Basins

Climate model predictions in temperature and precipitation regimes over the Pacific Northwest suggest that a general warming conditions and a range of various precipitation scenarios are very likely in the future. These predicted changes may impact hydrological processes in a watershed and thereby may change flow regimes in a river system. In order to preserve the integrity of these river basins and manage the water resources sustainably, it is critical to evaluate and understand how the climate change phenomenon and its inherent variability impacts can manifest itself in the basin. Studying the uncertainty associated with the water balance and flow regimes is not just important but essential for a sustainable resource management. This study characterizes uncertainty associated with streamflows and evapotranspiration projected due to impacts of climate change in the form of their probability distributions and associated parameters in selected basins in the Pacific Northwest. A complete characterization of uncertainty associated with streamflows will help watershed stakeholders and managers to make appropriate management decisions. We employ an ensemble of GCM-downscaled outputs, including CMIP3 and NARCCAP for the periods 2010-2100 to evaluate uncertainty associated with stream flows.