Summary:

The Brzeg Dolny Dam functioning since the year 1959 consists of a fivegate weir, sluiceway, powerhouse and a fishpass. The concrete pool pass has 26 chambers separated by vertical cross-walls each with one top notch and one submerged bottom orifice positioned alternately. The bottom of each following chamber, beginning from the inlet, drops by approx. 30 cm. Connection with tailwater is available through 3 entrances one above the other, what enables water supply within a wide range of head- and tailwater levels. Field studies and hydraulic analysis of the pass permitted to estimate its operation effectiveness confronted with the changed water level on the weir from 108.00 m.a.s.l. to 107.50 m.a.s.l. and lowered tailwater level due to river bottom erosion. The study showed that the fishpass sustained its function. This paper also presents recommendations towards the improvement of the pass functioning by its conversion into vertical slot pass and by the use of electric-electronic barriers protecting fishes from getting into turbines and directing them to the pass.