Our objective is to estimate seasonal snow volumes, relative to historical trends and extremes, in snow-dominated mountains that have austere infrastructure, sparse gauging, challenges of accessibility, and emerging or enduring insecurity related to water resources. To judge feasibility, the proposed effort looks at two regions, a validation case and a case representing the characteristics outlined above. For the validation case, we propose to use the Sierra Nevada of California, a mountain range of extensive historical study, emerging scientific innovation, and conflicting priorities in managing water for agriculture, urban areas, hydropower, recreation, habitat, and flood control. For the austere regional focus, we will examine southwest and south Asia, where some of the most persistent drought in the world causes food insecurity and combines with political instability, and occasional flooding, to affect US national security. Our approach will use a mix of satellite data and a spare modeling approach to present information essential for planning and decision making, ranging from optimization of proposed infrastructure projects to assessment of water resources stored as snow for seasonal forecasts. We will combine optical imagery (MODIS on Terra/Aqua, VIIRS on NPP), passive microwave data (SSM/I, AMSR-E), retrospective reconstruction with energy balance calculations, and gridded feed-forward, uncoupled land surface modeling to establish retrospective context. Specifically, we will use the period spanning the decade-long record from Terra and Aqua to bracket the historical record. In the California Sierra Nevada, surface measurements have sufficient spatial and temporal resolution for us to validate our approach, which we will extend to the Hindu Kush of High Asia where surface data are sparse and where access presents significant difficulties. The world's mountains accumulate substantial snow and, in some areas, produce the bulk of the runoff. In ranges like Afghanistan's Hindu Kush, availability of water resources affects US policy, martial and humanitarian operations, and national security. The rugged terrain makes surface measurements difficult and also affects the analysis of remotely sensed data. The analysis would leverage several techniques developed from NASA-sponsored research and use NASA instruments. While using data from the Sierra Nevada for validation, the activity would also improve water resource assessment in that region where statistically based forecasts occasionally produce significantly errors. Partner organizations include the US Army Corps of Engineers and the NOAA Office of Hydrology, organizations that work together in the NOAA-led IWRSS (Integrated Water Resources Science and Services).