特集: 魚道の評価 FEATURES: EVALUATION OF FISHWAYS
原著論文 ORIGINAL PAPER

農業利水との調和に配慮した 取水堰付設魚道の実験的検討

常住直人¹⁾・ 中達雄²⁾・ 加藤 敬²⁾

1) 北陸農業試験場（前農業工学研究所)　〒943-0193 新潟県上越市稲田1-2-1
2) 農業工学研究所　〒305-8609 茨城県つくば市観音台2-1-2

Naoto TSUNESUMI¹⁾, Tatso NAKA²⁾, Takashi KATO²⁾: Experimental study of fishways for harmonization of irrigation facilities with environmental conservation Ecol. Civil. Eng. 3(2), 179-192, 2000.

1) Hokuriku National Agricultural Experiment Station, 1-2-1, Inada, Joetsu, Niigata 943-0193, Japan
2) National Research Institute of Agricultural Engineering, 2-1-2, Kannondai, Tsukuba, Ibaraki 305-8609, Japan

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.

Key words: fishway, boatway, headwork, hydraulic design, open channel

摘要

近年，取水堰付設魚道については，生物多様性保全の見地から水産重要魚種のみならず，より多様な魚種に対応したものが求められるようになりつつある．その際，問題になるのは農業利水と魚道機能の向上を如何に調和させるかということである．本報文では最近，近自然工法の一環として採用事例が増えつつある粗石付き斜路式魚道につき，利水等との調和を図りつつ多魚種対応が可能か否かを実験的に検討した．
その結果，局所流況に着目して粗石形状・粗石配置を設定すれば，魚道勾配1/40では通常の堰上げ水位変動範囲で大型魚から小型魚・底生魚まで遡上可能な流況が保たれること，浮遊流下物による閉塞抑制を図るべく粗石を水没させた状態（維持管理が比較的容易かつ低廉な流況）での魚道運用が可能なことが明らかとなった．また，魚道放流量の管理に役立てるべく，当該魚道の上流水位―放流量曲線も示した．
なお，本魚道は漁労用舟通しも兼用させたため，魚道内表面流速が比較的遅く魚道流況としては若干余裕が見られる状態であった．魚道機能に特化させれば更なる大水深や1/40を超える急勾配でも上記と同機能の流況が保たれる可能性がある．

2000年7月27日受付, 2000年11月8日受理
1) e-mail: azum@inada.affrc.go.jp