Climate is changing, with serious though still unknown impacts expected within decades. Water resource planning and policy is implemented over similar timescales, and must therefore incorporate consideration of these impacts, even while their details are still unknown. The Indices of Hydrologic Vulnerability (IHV) presented in this thesis is an analytical methodology offering model-based representation of key riverine ecosystem drivers, which can be altered under climate scenarios. It allows landscape scale assessment of the vulnerability of water resources, ecosystem services, and biophysical habitat. A test application of the IHV methodology models climate warming of 2, 4, and 6 °C in the western Sierra Nevada, California, USA. Several of the specific climate change impacts modeled show alterations similar to predictions made by previous research, such as a snow-to-rain precipitation transition, and earlier snow melt. A composite vulnerability index for generalized aquatic and riparian ecosystem function (V_h) shows vulnerability rising with increasing temperature. Significant vulnerability (high V_h) is generally seen during initial stages of warming, except in the very high elevation subwatersheds which are buffered against impacts while they remain above the frost line. The central Sierra appears to be more vulnerable than the colder northern region or higher-elevation southern regions. Greatest vulnerability was also seen at mid- to high-elevation areas, with lower vulnerabilities calculated in both the upper and lower watersheds. As it is based on modeled hydrology, geographical information, and historical weather patterns, IHV can be applied to regional research questions regarding particular climate or water management scenarios of interest, or can be specialized to predict vulnerability of relevant ecosystem drivers and services. With development of a user interface, IHV will be a useful tool for managers, researchers, policy makers, and conservationists.