Our conceptual model includes five stream types: 1) bedrock channels entirely confined by exposed bedrock and devoid of persistent alluvium 2) bedrock with alluvium channels at least partially confined by bedrock but containing enough alluvium to create bedforms that persist through time 3) incised alluvium channels bound only by unconsolidated alluvial material into which they are incised 4) braided washes that exhibit multi-thread, braided characteristics regardless of the composition of confining material and 5) piedmont headwater 0-2nd order streams (Strahler) confined only by unconsolidated alluvium and which initiate as secondary channels on piedmont surfaces. To investigate the influence of channel characteristics on riparian vegetation in the arid southwestern United States, we develop a geomorphic classification for arid ephemeral streams based on the degree of confinement and the composition of confining material that provide constraints on available moisture. Relatively infrequent hydrologic disturbances in dryland environments are responsible for creation and maintenance of channel form that supports riparian communities. Interactions between hydrology, channel form, and riparian vegetation along arid ephemeral streams are not thoroughly understood and current stream classifications do not adequately represent variability in channel geometry and associated riparian communities. The primary disadvantage is that temperature profiles represent the continuous percolation rate at a single point in an ephemeral channel rather than an average seepage loss from the entire channel.ĭistinctive channel geometry and riparian vegetation: A geomorphic classification for arid ephemeral streams The most significant advantage of the use of sedimentâ€temperature profiles is their robust and continuous nature, leading to a longâ€term record of the timing and duration of channel losses and continuous estimates of streambed percolation. The difference is reasonable since channel losses include both vertical and nonvertical component of channel loss as well as potential evapotranspiration losses. Comparisons of temperatureâ€based streambed percolation rates with surface waterâ€based channel losses indicate that percolation rates represented 30% to 50% of the total channel loss. These results are combined with published results to develop conclusions regarding the accuracy of using vertical temperature profiles in estimating channel losses. Temperatureâ€based percolation rates for three ephemeral stream sites are compared with available surface water estimates of channel loss for these sites. The present work provides a detailed examination of the basis for using heat as a tracer of stream/groundwater exchanges, followed by a description of an appropriate heat and water transport simulation code for ephemeral channels, as well as discussion of several types of temperature analysis techniques to determine streambed percolation rates. Earlier work suggests that analysis of streambed temperature profiles is a promising technique for estimating streamflow patterns in ephemeral channels. The extremely transient nature of ephemeral streamflows results in shifting channel geometry and degradation in the calibration of streamflow stations. Sarma, LisaĬontinuous estimates of streamflow are challenging in ephemeral channels. Analysis of temperature profiles for investigating stream losses beneath ephemeral channelsĬonstantz, Jim Stewart, Amy E.
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