3.1. Studies on pool-and-weir fishways

Studies on pool-and-weir fishways were carried out in the new experimental hall of the Water Resources and Environmental Engineering Laboratory, University of Oulu, Finland in 1999 (Fig. 7). These studies were carried out in a straight channel with several discharges and slopes and using three pool lengths and one weir height.

The pools were constructed inside an experimental channel. Water into the model was conducted from the equalizing flume through the head tank with a well-designed inlet. From the model water ran through a collection well back into the collection tank. One wall of the flume is made of polycarbonate while the other wall, the bottom and the baffles are of plywood. The model width was 280 mm and length about 3 100 millimeters (Fig. 8). It was installed inside a flume, which was 600 mm wide.

A simple tilting arrangement is used to set the model to any desired slope. Discharge is controlled by a valve and determined by a Thompson weir, which is set after the model.

The weir heights were 190 mm for all studies, and three different spacings were used: 170 mm, 340 mm and 500 mm. For all the spacings, the experiments were carried out with three slopes, 5 %, 7 % and 10 %. Discharges varied from 0.4 l/s to 28.3 l/s with flow patterns ranging from plunging to streaming. Vertical water depths at the weir were measured at the centerline of the flume in the region of fully developed flow by using a ruler. The flow was visualized with dye. Photographs were taken of flow patterns with each of the weir spacings at the slope of 10 %. Velocity measurements were not carried out due to small water depths at the weirs.