Jeffrey Kampman, Paul D. Hoppe, Emma Rosi-Marshall, Ted Kennedy, Holly Wellard, Wyatt Cross, and Bob Hall

Alterations of temperature and discharge associated with hydroelectric power are a significant factor influencing benthic invertebrates inhabiting downstream reaches.  Releases from Glen Canyon Dam result in uniformly cold water temperatures at ca. 10 °C and water velocity can fluctuate more than 3 fold daily.  We are measuring the combined influence of temperature and fluctuating water velocities on algal resources and invertebrate communities.  We are using 18 artificial streams with 3 velocity treatments: stable flows, low fluctuating flows (LFF), and high fluctuating flows (HFF).  Within each of the 3 velocity treatments, stream temperature in half of the 6 replicates will simulate typical release temperatures (i.e., ~10°C) and half will simulate potential release temperatures associated with a temperature control device (i.e., ~15°C).  After three months, the 15°C streams influenced higher rates of primary production than the 10°C streams.  The stable 15°C and both high-fluctuation temperatures show increased rates of microbial respiration and both HFF and LFF 15°C treatments show increased GPP.  Results suggest higher rates of scouring among velocity treated streams, yielding higher rates of GPP while lowering concentrations of AFDM and chlorophyll a.  Measuring the effects of temperature and velocity on basil resources will provide a basis for understanding the subsequent effects on invertebrate communities.