Abstract
These years, environmental conservation has been regarded as a more important part of irrigation projects than before. Accordingly, it has been required that many fishes including non-fishery species are able to make migration through irrigation barrages. It has been also required, however, to harmonize improvement of fishway performance with operations of the irrigation barrage. In this study, we investigated on spatial patterns of local flow velocity in a boulder-paved fishway, aiming at examination of its performance for upstream migration. The local flow regimes were compared through hydraulic tests among several kinds of fishways differed in boulder shape, patterns of boulder arrangement, and fishway slope. Results indicated that a boulder-paved fishway could guarantee easier maintenance against partial blockage with drift stuff by submerged boulders and migration routes for many fish species by separation of their routes, serving both upper routes for large fishes and bottom routes with enough resting areas behind boulders for benthic and small fishes.
