Chris Frans, Erkan Istanbulluoglu, Dennis P. Lettenmaier, Garry Clarke, Theodore J. Bohn and Matt Stumbaugh. 2016. Implications of decadal to century scale glacio-hydrological change for water resources of the Hood River Basin, OR U.S.A. Hydrological Proc

In partially glacierized watersheds, mountain glaciers are an important source of water. Precipitation patterns are often highly season, with snow and ice masses redistributing seasonal precipitation when there are few other sources of streamflow. Consequently, glaciers provide a natural buffering of low flows. However, systems that rely on this buffering are particularly vulnerable to climate change. This new study, led by Chris Frans, formerly of the University of Washington and now at the US Army Corps of Engineers, looks at the evolution of glacier melt contribution in watershed hydrology over a 184-year period, from 1916-2099, incorporating two future climate scenarios (RCP 4.5 and 8.5) for the Hood River Basin in Northwest Oregon. The authors use a coupled hydrological and glacier dynamics model to perform continuous simulations of glaciological processes (including mass accumulation and ablation, lateral flow, and heat conduction). These processes are also key for other hydrological processes, such as snow dynamics and evapotranspiration. They find that the contribution of glacier melt to basin water supply was 79% in some parts of the basin historically. However, projected changes in climate will lead to a 14-63% or 18-78% reduction (RCP 4.5 and 8.5, respectively) in dry season discharge. The largest losses will occur at upland locations that were historically dominated by glacier melt and seasonal snow melt. Some losses will be modulated by supraglacial debris on the Hood River glaciers, which slows glacier recession. Additionally, the authors find large decadal variability in glacier melt, which underscores the need to use long time series in studying glacier recession.