Author(s): Lennart Billfalk
Linked Author(s): Lennart Billfalk
Keywords: No Keywords
Abstract: In order to facilitate ice cover formation and thereby reduce ice jamming at freeze-up on the river reach downstream of Vittjarv hydro power station in northern Sweden, exstensive excavations have been undertaken. In spite of the work carried out, ice jamming still occured resulting in head-losses and inundations. As a measure against the ice jamming it was suggested to decrease the discharge when ice formation starts and keep it low until the river is satisfactorily ice covered. However, the problem is to reduce the flow in the lower part of the river and still be able to generate electricity at high capacity in stations along the upper parts of the river. This requirement can partly be met by prelowering of a "mid-river" reservoir. Considering the planning needed for the operation of the whole river system it is extremely important that the right time for the low discharge period is correctly predicted. The method worked out to cope with this problem includes monitoring of water temperatures and water levels, weather fore-casting, ice surveys etc. To speed up ice cover formation a specially designed ice boom has been tested. Also ice breaking and ice-sawing on reaches with rapid shore ice formation have been used. The paper presents details of the indicated method together with two years of practical field experience
Year: 1984