Implications of Glacier Recession for Water Resources

Thesis (Ph.D.)--University of Washington, 2015Numerical simulation models of hydrologic processes can be effective tools for inferring the consequences of environmental change for water resource systems. In river basins that originate in partially glacierized catchments traditional widely used hydrological modeling approaches are not suitable for prediction of these consequences as they lack a representation of the storage and movement of glacier ice reservoirs on the land surface. In the first part of the dissertation, a framework for applying a recently developed complex glacio-hydrological model suitable for these predictions is described. This methodology was applied to a well instrumented heavily glacierized watershed in the Bolivia Andes. Using long-term projections of climate change constructed from CMIP5 Global Climate Model (GCM) outputs using a stochastic weather generator the model framework was applied to predict evolving hydrological processes from 1987-2100. These predictions served as a baseline for testing sensitivities of hydrological response to model structure and parameter selection. The importance of local insitu data to guide calibration and parameter selection of complex glacio-hydrological models is demonstrated. Debris cover on glaciers can retard ablation on the surface of glaciers, significantly affecting the rate of response to warming temperatures. In the second part of this work, algorithms that represent the storage and conductance of heat through supraglacial debris on glacier surfaces were developed into the glacio-hydrological model described in part 1. These model developments were tested against point measurement of ablation underneath debris. Model simulations indicate the relative role of debris cover on the evolution of glacier area and summer discharge in upland drainages in the Hood River Basin, OR. Furthermore, this work is used to demonstrate strong inter-decadal patterns of glacio-hydrological processes that are superimposed on the response to a longer term trend from a warming climate. This highlights the timescales of analysis required to evaluate hydrological response to glacier recession. The third and last topic of this dissertation focuses on regional patterns of glacio-hydrological response in the Pacific Northwest United States. This chapter describes a modeling study with specific emphasis on the following research objectives: (1) characterize how hydrological response to glacier recession varies within the region; (2) identify vulnerable downstream locations in space and time; and (3) quantify at which spatial scales glacier melt is a significant contributor to discharge patterns. The long-term coupled glacio-hydrological response for a sample of watersheds that span sharp climatic gradients (maritime to continental), a range of temperate northern latitudes (45-49°), and varying local physiological attributes (e.g., range of elevations, wind/leeward) in the Pacific Northwestern United States (PNW) is predicted