Quantifying Hydrological Uncertainty for Rain- and Snow-Dominated Watersheds with Adaptation Strategy

Hydrological uncertainty in climate change impact assessments on water resources was realized to vary significantly between watersheds. We investigated various uncertainty sources of hydrological impact assessment in two northwestern river basins in Oregon, USA. The Clackamas River Basin (CRB) is dominated by snowfall and snowmelt in the winter and spring seasons, and the Tualatin River Basin (TRB) is dominated by rainfall for all seasons. Eight global climate models (GCMs) simulation with two greenhouse gas (GHG) emission scenarios were used to consider the uncertainties arising from the translation of future GHG emissions into climate change by GCMs. The Precipitation Runoff Modeling System (PRMS) model was employed to assess the hydrologic uncertainty. Latin Hypercube Sampling (LHS) used to sample the PRMS model parameter space and estimate the behavioral parameter sets according to the Nash-Sutcliffe efficiency criterion. Our results show that changes in winter runoff are more affected by hydrologic model parameter uncertainty in the snowfall-dominated basin, while they are less affected in the rainfall-dominated basin. Additionally, summer runoff in the CRB is shown to decrease when compared with the TRB, although both watersheds were affected by the same climate change simulations. Water resource management in the two watersheds, particularly in the CRB, water manager must be adapted toward improving water supply capacity and reducing water demand. Our results could help water resource managers for decision making to establish adaptive water resources management under the stress of changing climate in both regions.