Map showing surficial geology, geologic structure, and chemical characteristics of ground-water discharge at selected springs and creeks along the south rim
Springs along the south rim of the Grand Canyon, Arizona, are important ecological and cultural resources in Grand Canyon National Park and are discharge points for regional and local aquifers of the Coconino Plateau. This study evaluated the applicability of electrical resistance (ER) sensors for measuring diffuse, low-stage (<1.0 cm) intermittent and ephemeral flow in the steep, rocky spring-fed tributaries of the south rim. ER sensors were used to conduct a baseline survey of spring flow timing at eight sites in three spring-fed tributaries in Grand Canyon. Sensors were attached to a nearly vertical rock wall at a spring outlet and were installed in alluvial and bedrock channels. Spring flow timing data inferred by the ER sensors were consistent with observations during site visits, with flow events recorded with collocated streamflow gauging stations and with local precipitation gauges. ER sensors were able to distinguish the presence of flow along nearly vertical rock surfaces with flow depths between 0.3 and 1.0 cm. Laboratory experiments confirmed the ability of the sensors to monitor the timing of diffuse flow on impervious surfaces. A comparison of flow patterns along the stream reaches and at springs identified the timing and location of perennial and intermittent flow, and periods of increased evapotranspiration.
The advent of Virtual Reality (VR) has created new user-interaction paradigms that VR designers need to attend to in order to avoid usability issues. Currently, there are few formal methods for evaluating the usability of VR interfaces. In this paper, we introduce a new set of heuristics that can be used to carry out usability inspections of VR systems via the Heuristic Evaluation method. The heuristics were developed to identify usability problems in both developing and currently-existing VR hardware and software. The heuristics reported here were developed by surveying VR users, and then using their data to identify nine classes of usability problems common to VR systems. The result is a new resource for UXRs who are seeking to use Heuristic Review to assess VR products.
Deep‐sea cores and ice cores from the late Cenozoic show that the Earth's climate changes significantly. Glacier fluctuations are but one indication of this change. Glaciers are both an active component of the environmental system, regulating mountain streamflow, and a passive one, responding to climatic change. Thus, an understanding of the link between climate and glaciers is needed in order to assess the potential effect of glacier variations on the water resources of glacierized regions.
To define the basic data collection program needed to achieve this goal, the Workshop on Glacier Mass‐Balance Standards was held November 28–29, 1990, in Seattle, Wash. Convened by the North American Committee on Climate and Glaciers, which was established in June 1990 at a meeting of the National Research Council of Canada's Subcommittee on Glaciers, the workshop was held to re‐examine current glacier climate and hydrology programs in Canada and the United States.
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