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Recently various types of fishways have been developed and constructed in order to preserve diversity of fish species and restore the riverine ecological system. Some of the fishways in Korea, however, seem to be designed and installed without careful study on their functions and swimming characteristics of target fishes. The present study aims to elucidate proper hydraulic characteristics of the Ice Harbor-type fishway. In the present study, we analyzed the hydraulic characteristics depending on changes in the spans of walls in the Ice Harbor-type fishways, by using Flow-3D, a three dimensional numerical simulation program. Two physical experiments were performed to verify the results of the program. The comparison between the physical model and the numerical model showed that the results of the numerical model are in good agreement with the physical opponent. A series of numerical simulation were performed with various pool-aspect ratios (the ratio of span of fishway to its width). The numerical simulations revealed that, as the spans of baffles widens, the flow velocities of entire area decreases and the flow velocity of orifice area increases. The results showed that the pool aspect ratio should be larger than 1.0 to avoid the streaming flow, where fish could not ascend easily. As the ratio increases, the recirculation zone develops at the vertical plane and the flow condition becomes an inclined flow, which is the proper condition for fish ascending.

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In this paper we explore the economic principle behind the revenue-sharing rule for interconnection charges. Our main finding is that symmetric firms can collude by splitting the revenues equally. We further characterize the optimal revenue-sharing ratio and discuss the relationship between optimal ratio and the optimal access price. We also show that the revenue-sharing rule can have the perverse effect of inducing a firm to raise its own costs in order to gain a higher share of revenues. JEL classification number: L11.