Robert Rice

Mountain hydrology of the western United States

Climate change and climate variability, population growth, and land use change drive the need for new hydrologic knowledge and understanding. In the mountainous West and other similar areas worldwide, three pressing hydrologic needs stand out: first, to better understand the processes controlling the partitioning of energy and water fluxes within and out from these systems; second, to better understand feedbacks between hydrological fluxes and biogeochemical and ecological processes; and, third, to enhance our physical and empirical understanding with integrated measurement strategies and information systems. We envision an integrative approach to monitoring, modeling, and sensing the mountain environment that will improve understanding and prediction of hydrologic fluxes and processes. Here extensive monitoring of energy fluxes and hydrologic states are needed to supplement existing measurements, which are largely limited to streamflow and snow water equivalent. Ground-based observing systems must be explicitly designed for integration with remotely sensed data and for scaling up to basins and whole ranges. Copyright 2006 by the American Geophysical Union.

Embedded‐sensor network design for snow cover measurements around snow pillow and snow course sites in the Sierra Nevada of California

The design of sensor networks for measuring the mean and spatial distribution of snow depth at the scale of 1-16 km2 was evaluated by deploying an embedded-sensor network consisting of ultrasonic snow depth sensors to capture the variable physiographic features around an operational snow course in Yosemite National Park in the Sierra Nevada of California. Manual snow surveys were also carried out during accumulation and ablation periods. Four years of continuous data from the embedded-sensor network showed that snow depths during both accumulation and ablation periods can vary as much as 50% based on variability in topography and vegetation across a 0.4 ha study area. Spatial snow surveys showed that such a sensor network can be deployed so as to capture both the variability and mean for accumulation and ablation periods across a 1 km2 area surrounding the sensor network, with a broader network required to extend this to 4 and 16 km2 areas. In forested areas, higher canopy densities, greater than 60% closure, were associated with the lowest snow depths. Analysis of historical snow course records from 14 sites in Yosemite, including the 10 spatial measurements made during each monthly snow course survey, showed snow depths across the 300 m snow course transects to be relatively uniform, with 68% of all monthly values having standard deviations no more than 10% of the mean. Although existing snow courses do little to help define the spatial patterns of snow distribution at the 1-16 km2 scales, it is feasible to extend the representativeness of current operational networks by deploying low-cost embeddedsensor networks nearby. Such networks should be strategically located to also capture elevational differences in snow accumulation and melt, as well as local-scale variability in canopy cover and aspect Copyright 2010 by the American Geophysical Union.

RURAL INTELLIGENT TRANSPORTATION SYSTEM NATURAL-HAZARD MANAGEMENT ON LOW-VOLUME ROADS

The growth of winter travel on alpine roads in the western United States has increased the risk to motorists and highway maintenance personnel owing to a variety of natural hazards. Hazards include snow and ice, avalanching snow, and blowing and drifting snow. The conditions call for attendant need for incident response. A substantial number of affected routes are low-volume rural winter roads. Configurations have been developed for rural intelligent transportation system (ITS) technology that can detect hazards and provide, autonomously and in real time, warnings to and traffic control actions for motorists, highway maintainers, and incident responders for roadway natural hazards. These warnings include on-site traffic control signing and road closure gates, in-vehicle audio alarms for agency maintenance and patrol vehicles, and notification to highway agency maintenance facilities or centralized multiagency dispatchers. These actions and notifications are initiated automatically from the remote rural sites and via manual intervention from off-site personnel, well removed from the rural roadway corridor itself. About 5 years of experience have been accumulated in using these rural ITS natural-hazard reduction systems, including snow avalanche detection and warning systems on Loveland Pass, Colorado; Hoback Canyon, Wyoming; and Banner Summit, Idaho. Automated road closure gates on the Teton Pass in Idaho and Wyoming now allow for remote road closure during heavy snow events. These cost-effective ITS natural-hazard systems are highly exportable for other processes that affect rural low-volume roadways, including landslide, flooding, high surf, high winds, loss of visibility, wildlife, and other natural hazards of this type.

Management Implications of Snowpack Sensitivity to Temperature and Atmospheric Moisture Changes in Yosemite National Park, CA

In order to investigate snowpack sensitivity to temperature increases and end-member atmospheric-moisture conditions, we applied a well-constrained energy- and mass-balance snow model across the full elevation range of seasonal snowpack using forcing data from recent wet and dry years. Humidity scenarios examined were constant relative humidity (high) and constant vapor pressure between storms (low). With minimum calibration, model results captured the observed magnitude and timing of snowmelt. April 1 SWE losses of 38, 73, and 90% with temperature increases of 2, 4, and 6°C in a dry year centered on areas of greatest SWE accumulation. Each 2°C increment of warming also resulted in seasonal snowline moving upslope by 300 m. The zone of maximum melt was compressed upwards 100-500 m with 6°C warming, with the range reflecting differences in basin hypsometry. Melt contribution by elevations below 2000 m disappeared with 4°C warming. The constant-relative-humidity scenario resulted in 0-100 mm less snowpack in late spring versus the constant-vapor-pressure scenario in a wet year, a difference driven by increased thermal radiation (+1.2 W m-2) and turbulent energy fluxes (+1.2 W m-2) to the snowpack for the constant-relative-humidity case. Loss of snowpack storage and potential increases in forest evapotranspiration due to warming will result in a substantial shift in forest water balance and present major challenges to land management in this mountainous region.