ABSTRACT: Quantifying Arctic lake underflows using a novel underflow sediment trap.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Underflows in lakes are important events that greatly affect sediment deposition patterns and bottom water chemistry. Currently, no feasible, cost-effective device or method has been regularly utilized to quantify sediment deposition fluxes and patterns associated with underflows, which are typically caused by high sediment loads ininflowing rivers and streams. This study utilizes a novel underflow trap design that was developed and tested for use in Arctic lakes. We report results of a study where underflow traps were deployed at a depth of 0.2m and 1m from bottom at two locations in a High Arctic lake subject to seasonal turbid river inflow. During the five year study, traps were collected in 3 to 6 day intervals from locations proximal and distal to the input river. The amount of sediment retained in the traps suggests underflow deposition decreases with distance traveled. The in situ study found that the timing of the peak underflow sediment deposition correlated with the beginning of lake bottom temperature departures, an increase in lake bottom turbidity, and a period of high river suspended sediment concentration. Underflow velocity data indicate that periods of increased velocities correspond with increases in trapped underfl ow sediment. In addition, the timing of underflow deposition amounts correlate well with maximum vertical sediment deposition periods at both stations in the lake. Preliminary laboratory testing of hydraulic properties has found that the trap orients itself into the underflow at medium to high water velocities, although quantitative trapping rates remain untested.Results show that use of underflow traps will help determine underflow conditions in lakes, determine sediment deposition patterns, and monitor the changes in the lake bottom waters. We anticipate that further refinement of this technique will provide new insights into the physical processes operating in Arctic lake bottoms.

Bibliography of Canadian Geomorphology