Abstract:Hyporheic exchange increases the potential for solute retention in streams by slowing downstream transport and increasing solute contact with the substrate. Hyporheic exchange may be a major mechanism to remove nutrients in semi-arid watersheds, where livestock have damaged stream riparian zones and contributed nutrients to stream channels. Debris dams, such as beaver dams and anthropogenic log dams, may increase hyporheic interactions by slowing stream water velocity, increasing flow complexity and diverting water to the subsurface.Here, we report the results of chloride tracer injection experiments done to evaluate hyporheic interaction along a 320 m reach of Red Canyon Creek, a second order stream in the semi-arid Wind River Range of Wyoming. The study site is part of a rangeland watershed managed by The Nature Conservancy of Wyoming, and used as a hydrologic field site by the University of Missouri Branson Geologic Field Station. The creek reach we investigated has debris dams and tight meanders that hypothetically should enhance hyporheic interaction. Breakthrough curves of chloride measured during the field experiment were modelled with OTIS-P, a one-dimensional, surface-water, solute-transport model from which we extracted the storage exchange rate˛and cross-sectional area of the storage zone A s for hyporheic exchange. Along gaining reaches of the stream reach, short-term hyporheic interactions associated with debris dams were comparable to those associated with severe meanders. In contrast, along the non-gaining reach, stream water was diverted to the subsurface by debris dams and captured by large-scale near-stream flow paths. Overall, hyporheic exchange rates along Red Canyon Creek during snowmelt recession equal or exceed exchange rates observed during baseflow at other streams.
ABSTRACT. Snow and firn properties control the transport of vapor, gases and water between the atmosphere and the underlying strata. An understanding of this transport and the properties that control it is important for predicting air-snow transfer of chemical species and for interpreting ice cores. Remote-sensing images of East Antarctica show large areas of alternating light and dark bands. These low-amplitude, long-wavelength features have glazed downwind faces and rough upwind faces and are called megadunes. The first linked measurements of the permeability and the associated microstructure for a glazed area within a well-defined megadune area are reported in this paper. Permeability and density were measured, along with grain-scale properties derived from digital image processing of preserved thick sections, at this cold, low-accumulation glazed site. A clear layering pattern exists. In the top meter the firn density ranges from 0.24 to 0.50 g cm -3
The Heritage Group is composed of about 7,500 m of sedimentary strata exposed in the Heritage Range of the Ellsworth Mountains, West Antarctica. The Heritage Group is here redefined to include the Minaret Formation as the uppermost unit. New formations within the Heritage Group are formally described; they are, from the bottom upward, the Union Glacier, Hyde Glacier, Drake Icefall, Conglomerate Ridge, Springer Peak, Liberty Hills, and Frazier Ridge Formations. The Kosco Peak Member of the Union Glacier Formation is also formally described.Deposition of the Heritage Group took place in Middle and early Late Cambrian time in a rapidly subsiding basin bordered by carbonate rock and quartzite source areas of moderate relief. Sediment transport directions were dominantly from the present south and west. Thick, volcaniclastic terrestrial strata lie at the exposed base of the group, and these rocks grade upward into deltaic black shale and normal marine sediments. A number of active volcanic centers were present in the Heritage Range during the deposition of upper Heritage Group strata.
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