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Presented at the NABS Annual meeting, Anchorage, Alaska, 2006
in Hyporheic Processes
Transient storage behavior across stream-reaches with varying discharge, groundwater influx, and bed form
C.D. Arp1, M.N. Gooseff2, and M.A. Baker1.1Department of Biology, Utah State Univeristy, Logan, Utah 84322, 2Department of Geology and Geological Engineering, Colorado School of Mines, Golden, CO 80401
Stream transient storage can have important implications for nutrient retention and other lotic ecosystem functions, but varies considerably with discharge and geomorphology. We conducted pulse injections of rhodamine WT in 6 stream reaches that varied in bedform and groundwater influx during snowmelt and baseflow, along with 6 additional injections at 2 reaches over a wider range of flows (18 injections total). Reach integrated transient storage parameters were estimated using OTIS coupled with multiple cross-section velocity profiles to estimate the proportion of storage due to in-channel dead zones (ASDZ). The relative storage zone size (AS/A) was consistently larger during baseflow compared to snowmelt, however ASDZ/A was larger during snowmelt. Reaches with pool-riffle beds had higher hyporheic storage (ASHZ/A) compared to plane beds, but ASDZ/A was similar among these bedform types. At one plane bed reach with strong groundwater influx, ASDZ/A increased with discharge (r2=0.75) and ASHZ/A decreased with discharge (r2=0.79). At a pool-riffle reach with neutral groundwater flux, opposite and weaker relationships were observed between discharge and dead zone (r2=0.35) and hyporheic storage (r2=0.21). The results suggest the in-channel storage can account for a substantial proportion of transient storage and that this proportion can vary widely depending on reach discharge and geomorphology.
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