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WATER QUALITY EFFECTS OF HYPORHEIC PROCESSING IN A LARGE RIVER
Citation:
Fernald, A. G., D H. Landers, AND P. J. WIGINGTON JR. WATER QUALITY EFFECTS OF HYPORHEIC PROCESSING IN A LARGE RIVER. Riparian Ecology and Management in Multi-Land Use Watersheds, Portland, OR, August 28-31, 2000.
Description:
Water quality changes along hyporheic flow paths may have
important effects on river water quality and aquatic habitat. Previous
studies on the Willamette River, Oregon, showed that river water follows
hyporheic flow paths through highly porous deposits created by river
channel meandering. To determine water quality changes associated with
hyporheic flow, we studied six bar deposits positioned between the river
and closed lentic side-channel alcoves. At each site we measured water
levels and water quality in river, hyporheic, and alcove water. At all
sites we found hyporheic flow paths from the river through the bar deposits
to the alcove surface water. At a majority of the sites hyporheic
dissolved oxygen and ammonium decreased relative to river water, while
hyporheic specific conductance, nitrate, and soluble reactive phosphorous
increased compared to the river. At three sites with fast hyporheic flow
rates, hyporheic temperature decreased relative to river water, and there
was little change in temperature at the other three sites. Hyporheic
changes most affected receiving alcove water quality at sites with fast
hyporheic flow rates. Strategies to promote ecosystem functions provided
by hyporheic flow should focus on restoring natural hydrogeopmorphic river
channel processes to create high porosity deposits conducive to hyporheic
flow.