Abstract:The Distributed Hydrology Soil Vegetation Model is applied to the Redfish Creek catchment to investigate the suitability of this model for simulation of forested mountainous watersheds in interior British Columbia and other high-latitude and high-altitude areas. On-site meteorological data and GIS information on terrain parameters, forest cover, and soil cover are used to specify model input. A stepwise approach is taken in calibrating the model, in which snow accumulation and melt parameters for clear-cut and forested areas were optimized independent of runoff production parameters. The calibrated model performs well in reproducing year-to-year variability in the outflow hydrograph, including peak flows. In the subsequent model performance evaluation for simulation of catchment processes, emphasis is put on elevation and temporal differences in snow accumulation and melt, spatial patterns of snowline retreat, water table depth, and internal runoff generation, using internal catchment data as much as possible. Although the overall model performance based on these criteria is found to be good, some issues regarding the simulation of internal catchment processes remain. These issues are related to the distribution of meteorological variables over the catchment and a lack of information on spatial variability in soil properties and soil saturation patterns. Present data limitations for testing internal model accuracy serve to guide future data collection at Redfish Creek. This study also illustrates the challenges that need to be overcome before distributed physically based hydrologic models can be used for simulating catchments with fewer data resources.

This paper describes the Denali isolation kernel, an operating system architecture that safely multiplexes a large number of untrusted Internet services on shared hardware. Denali's goal is to allow new Internet services to be "pushed" into third party infrastructure, relieving Internet service authors from the burden of acquiring and maintaining physical infrastructure. Our isolation kernel exposes a virtual machine abstraction, but unlike conventional virtual machine monitors, Denali does not attempt to emulate the underlying physical architecture precisely, and instead modifies the virtual architecture to gain scale, performance, and simplicity of implementation. In this paper, we first discuss design principles of isolation kernels, and then we describe the design and implementation of Denali. Following this, we present a detailed evaluation of Denali, demonstrating that the overhead of virtualization is small, that our architectural choices are warranted, and that we can successfully scale to more than 10,000 virtual machines on commodity hardware.

This paper describes the Denali isolation kernel, an operating system architecture that safely multiplexes a large number of untrusted Internet services on shared hardware. Denali's goal is to allow new Internet services to be "pushed" into third party infrastructure, relieving Internet service authors from the burden of acquiring and maintaining physical infrastructure. Our isolation kernel exposes a virtual machine abstraction, but unlike conventional virtual machine monitors, Denali does not attempt to emulate the underlying physical architecture precisely, and instead modifies the virtual architecture to gain scale, performance, and simplicity of implementation. In this paper, we first discuss design principles of isolation kernels, and then we describe the design and implementation of Denali. Following this, we present a detailed evaluation of Denali, demonstrating that the overhead of virtualization is small, that our architectural choices are warranted, and that we can successfully scale to more than 10,000 virtual machines on commodity hardware.

[1] A hydrologic model of the mountainous snowmelt-dominated Redfish Creek catchment (British Columbia) is used to evaluate Interior Watershed Assessment Procedure (IWAP) guidelines regarding peak flow sensitivity to logging in different elevation bands of a basin. Simulation results suggest that peak flow increases are caused by greater snow accumulation and melt in clear-cut areas while similar evapotranspiration rates are predicted under forested and clear-cut conditions during spring high flow. Snow accumulation and melt are clearly related to elevation, but the relationship between logging elevation and peak flow change is more complex than perceived in the IWAP. Logging in the bottom 20% of the catchment causes little or no change in peak flow because of the small low-elevation snowpack and the timing of snowmelt, while clear-cut area alone appears to be a good indicator of peak flow increases due to logging at higher elevation. Temporal variability in peak flow changes due to clear-cutting is substantial and may depend more on temperatures during snowmelt than on the size of the snowpack. Long-term simulations are needed to improve quantitative estimates of peak flow change while the importance of watershed topographic characteristics for snowmelt and peak flow generation must be further examined.