Hydrological disturbance is a key force structuring stream communities as hydrologic regime affects the abundance, distribution, and behavior of stream organisms.  Streams frequently experience natural hydrological disturbance, but are also undergoing considerable anthropogenic disturbance due to dam construction and water diversion.  We explored the potential impacts of water diversion on aquatic insects and fish by experimentally diverting stream flow in three northeast Connecticut streams.  We diverted water over a 100m reach for three months in the summers of 2005, 2006, and 2007.  We also had an un-diverted 100m control reach for each treatment stream and three un-manipulated reference streams.  In diverted reaches, August mean flow was reduced by 50-80% and the seven-day minimum flow was reduced by 65-95%.  As a result diverted reaches experienced a reduction in the amount of available wetted habitat area and a shift towards more pool and less riffle habitat.  We did not find significant shifts in fish abundance or density, but there were some shifts in size structure.  Preliminary analysis suggests a decrease in aquatic insect abundance as a result of water diversion.  We are currently conducting further analysis to explore the effect on aquatic insect biomass and community composition.