Rehabilitation of fishery significance of small and medium rivers can be achieved by creating required areas of spawning for anadromous fish including those artificially built. It was established that in spite of diversity of existing home and foreign designs there is no construction of artificial spawning which can be implemented at small and medium rivers when there is no a dam or reservoir with accumulated water resources in the upstream or because of their complexity. The developed by the authors radically new construction of spawning complex for small and medium rivers allows creating favorable conditions for reproduction either lithophilic or phytophilous fishes. The construction includes bottom sill, which conducting a local head of water, and riverbed shooting flow part. Spawning complex doesn’t dike the entire cross-section of a river, doesn’t block transit ways of spawning fish migration and can be settled in riverbed sequentially. As a result, along the river, an artificial spawning of required area for efficiency reproduction of anadromous fish species can be created. Assuming the specifics of spawning of particular species of anadromous fishes, a modification of the riverbed spawning complex with shooting flow as a number of benches was developed. For both varieties of spawning complex a methodology for calculating geometric and hydraulic parameters was developed. For small rivers, the part of the construction of shooting flow is recommended to make a complex profile as a deepen stream of trapezoid cross-section in its center and widen horizontal shelves. Central stream works in water-short years (with runoff probability (Ð) less than 25 %), and horizontal shelves together with central part perform functions of spawning in high-water years (Ð ≥ 25 %) or their periods. For medium rivers the cross-section profile of a riverbed spawning complex is recommended to make as a trapezoid with slopes m = 2…3. The obtained results enabled to design and build a riverbed spawning complex at the river Kundruchya in 9 kilometers from its mouth.
Keywords: riverbed spawning complex, hydrologic and hydraulic regime, fishery discharge, spawning parameters, spawning of compound profile.
