The main objective of this work was to study the hydraulics of pool and weir fishways, for wider range of bed slopes, weir spacing, and heights, so that they can be designed to allow the passage of different species and sizes of fish. This laboratory study contains the results of 435 experiments, including the flow regimes, main flow characteristics and velocity profiles for several discharges. The flow regimes may be classified into plunging, transitional, streaming, and supercritical jet flows. A diagram has been developed to predict the different flow regimes using two dimensionless variables, Qt* and L/p. The dimensionless discharge Q+ for plunging flows was found to follow the Rehbock equation while Q* assumed a constant value equal to 5.75 for streaming flows. Velocity profiles in plunging as well as in streaming flows were found to be similar and correlations have been developed for the velocity and length scales. If the present work is considered to be a scale-model study, the scale would be approximately 10. Key words: fishways, pools and weirs, hydraulics, turbulent flow, energy dissipation, fisheries management.