Appendix 2. Pool and weir fishways – studies at the University of Alberta, Canada
The experimental work at the University of Alberta on pool-and-weir fishways was performed in a 0.31-meter-wide flume with an aluminum bed and plexiglass sides of a height of 0.57 meters and a length of 4.9 meters. The flume was equipped with weirs. The height of the weirs was 0.21 m, and they were cut from 6-mm-thick aluminum plates.
Water was supplied at the upstream end of the flume from two parallel pumps and the flow rates were measured with magnetic flow meters. A tailgate was provided at the downstream end of the flume for downstream depth control. The flow depths, head over the weirs, as well as the depth of the streaming flow, were measured to the precision of 1 mm. The flow pattern in the pools in the middle of the flume was observed with a tuft-grid. In every experiment, using the tuft-grid and dye-injection, the flow was classified as either plunging or streaming. Depending on the state of flow, either the head over the weir or the depth of the flow over the weirs was measured (Fig. A2.1). For the transition state, both depths were measured.
Three series of experiments were conducted with four slopes of 2%, 5%, 10% and 15%. For each of the slopes, experiments were performed with several increasing flow rates so that the flow passed (generally) from plunging to streaming states. For the first series, nine pools were constructed in this flume, with the length of each pool equal to 0.376 m. For the second series, the pool length was 0.18 m and for the third series the pool length was 0.57 m. Experimental data is given in Rajaratnam et al. (1987).
In general, it was observed that for a given slope and a given pool length, the transition from plunging to streaming flow occurred when flow rate exceeded a certain value. This transition occurred earlier as the pool length was reduced or as the slope was reduced. For smaller slopes and shorter pools, the streaming flow was smooth and the surface stream had an almost constant thickness, whereas for the larger slopes with longer pools, the streaming flow had a wavy appearance and in some cases, contained undular surface jumps over a portion of its total length.
1.1 Reports and papers
Rajaratnam N, Katopodis C & Mainali A (1987) Pool and weir fishways. Technical report (WRE 87-1). Department of Civil Engineering, University of Alberta, Edmonton, Alberta. 10 p. + figures and tables.
Rajaratnam N, Katopodis C & Mainali A (1988) Plunging and streaming flows in pool and weir fishways. Journal of Hydraulic Engineering, ASCE 114: 939-944.
Sikora G, Rajaratnam N & Katopodis C (1996) A photographic study of pool and weir fishways. Technical report (August 1996-SRK1), Department of Civil Engineering, University of Alberta, Canada. i-v, 224 p. photos.