"Computer recipe" for salmon's wellbeing

Svein Tønseth

The electricity company has now built pools and artificial rapids as suggested by the two scientists, in the hope of created good growth conditions for salmon in this regulated river.

The computer program used by Harby was developed by SINTEF NHL (Norwegian Hydrotechnical Laboratory), and it is one of a number of subprograms that make up the river simulator that is being tested in connection with the recently completed hydroelectricity development in the mountain village of Meråker.

The subprogram that has been employed to model the Dålåa River shows how current speeds, water depth and temperature, and river-bed material change after interventions in a river system. When they use the model, the SINTEF NHL scientists collaborate closely with biologists. Used in conjunction with the biologists' knowledge of the physical conditions preferred by the fish, the computer simulations show how living conditions for the fish are altered by specific changes in water supply or other effects on the river.

The licence for the Meråker development required the developer to release salmon fry into the river, in which much less water flows than it used to.

"We want to determine the lowest flow rate and to identify other measures in the river that will provide living conditions for the salmon without wasting water. SINTEF NHL's computer model means that we feel more likely to arrive at good results than we would have done by trial and error" says Bjørn Høgaas of Nord-Trøndelag Electricity Company.