The Hienuki River, Iwate, Japan, originates on Mt. Hayachine.  Construction of the Hayachine surface-release dam on the river was completed in 2000.  In 2002, we sampled macroinvertebrates and algae at three sites: upstream of the reservoir, at the outlet and downstream. The aquatic community was negatively affected at the dam outlet, but recovery occurred within 4 km. Causes of community change may include elimination of drifting aquatic insects from upstream, fluctuations in water flow, and destruction and alteration of food sources. Changes in food sources included changes in algal growth and reduction of CPOM, which resulted in the elimination of shredders.  Flow manipulation may cause alteration of the algal community at the outlet, which in turn caused a reduction of scrapers. The abundance of blackfly larvae increased over the summer as the abundance of the caddisfly species (Hydropsyche orientalis) gradually decreased.  This decrease may have been the result of competition between these filter-feeders.  It is concluded that surface-release features of Hayachine dam appear to be similar to a natural lake on a river, where changes are minimal, and recovery is very rapid – within about 4km, compared to about 100 km in the case of dams with hypolimnion drains.