HR: 0830h
AN: H41D-1034    [PDF]
TI: Stream-Upland Connections and the Effects of Stream Discharge on Transient Storage Processes
AU: * McGlynn, B L
EM: bmcglynn@montana.edu
AF: Montana State University, Department of Land Resources and Environmental Sciences 334 Leon Johnson Hall, Bozeman, MT 50717 United States
AU: Gooseff, M N
EM: michael.gooseff@usu.edu
AF: Utah State University, Department of Aquatic, Watershed, and Earth Resources, Logan, UT 84322-5210 United States
AU: McGlynn, R S
EM: Robert.McGlynn@Dartmouth.edu
AF: Dartmouth College, Department of Earth Sciences, Hanover, NH 03755 United States
AB: Stream-upland connections and the linkages between stream discharge and transient storage processes remain poorly understood. Previous studies of transient storage in streams have suggested that hyporheic exchange should dominate transient storage as discharge decreases because of reduced stream cross-sectional area relative to the cross-sectional area of the hyporheic zone. However, no direct relationships have been developed between stream discharge and transient storage influences on solute transport. We tested the hypothesis that the influence of transient storage on solute transport increases with decreasing stream discharge. We performed three separate conservative tracer stream additions with LiBr during baseflow recession (over 12 days) in a 16.9 ha headwater catchment, at Maimai New Zealand. Breakthrough of bromide was measured and simulated with OTIS for four sub-reaches within the 580 m study reach (145 m, 290 m, 425 m, and 580 m from the injection point). Discharge decreased from 1.11 to 0.14 l s-1 at the injection point, and from 4.5 to 1.5 l s-1 at 580 m over the course of the three tracer tests. The storage zone area to stream area ratio (AS/A) increased with decreasing stream discharge and average lateral inflows to the stream decreased as stream discharge decreased. This effect was more pronounced in the headwaters where baseflow decreased at a higher rate than in reaches closer to the catchment outlet. We also tested the linkage between local subsurface water inflow to the stream channel and lateral upland accumulated area. We synoptically sampled tracer concentrations at steady state during the first and third tracer test. We compare calculated lateral water inflows to upland area inputs computed with terrain analysis of a digital elevation model of the catchment. We suggest that improved understanding of transient storage within particular reaches is possible with improved understanding of stream-upland connections and repeated solute tracer experiments at varying discharge. A single tracer test at one discharge does not provide a representative measure of transient storage for the same reach at another discharge, and is insufficient for comparison among streams.
DE: 1806 Chemistry of fresh water
DE: 1824 Geomorphology (1625)
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
DE: 1871 Surface water quality
SC: Hydrology [H]
MN: 2003 Fall Meeting