Document Type

Honors Paper

Advisor

Douglas Thompson

Publication Date

2017

Abstract

The fluvial geomorphic process of hyporheic flow provides critical nutrients and dissolved oxygen to macroinvertebrates and eggs within riverbeds through hyporheic exchange. Hyporheic flow may operate at similar scales within sea lamprey (Petromyzon marinus) redds. Limited documentation exists on the hyporheic processes within lamprey redds. This study attempts to measure hyporheic flow using a saline injection syringe and salinity probe to record salinity-time curves. The method was applied to several redds on the Blackledge River, Marlborough, Connecticut. The second aspect of this study examined the hydraulic properties of lamprey redds within a controlled environment in a 0.5 m by 6 m flume at Connecticut College, New London, Connecticut. A 50% scale redd was constructed and velocity measurements were taken using an acoustic Doppler velocimeter at three different discharges. The salinity syringe provided moderate success in measuring the percent change of salinity and decay rate, with the strongest correlation at the beginning of the mound, but failed to provide accurate intergranular velocity measurements. The results of the flume study indicate strong areas of downwelling and upwelling at the pit and mound, respectively. Turbulent kinetic energy (TKE) is highest over the mound, indicating different pressures that may induce hyporheic flow through the redd mound. Velocity was the slowest downstream of the mound for all three discharges, and mean vertical velocity (Vz) values increased then decreased rapidly moving downstream over the mound. Although the hyporheic flow was not directly measured, the results reveal that lamprey redds influence localized velocity patterns and create low pressures downstream of the mound, which should enhance hyporheic exchange.

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The views expressed in this paper are solely those of the author.