Do representative river sections exist?

26.11.2017 16:06

We know by observations from more than fifty years in the laboratory of rivers that rivers constantly change, that rivers are dynamic and the river gravel more or less move all the time. One year it goes 600 m/s in a flood and the river is wide and large, another year the power station holds back the floods in a dam and the river is small and narrow. There is no representative or typical river section because the river always moves in all directions and calculations using river section flow will be too late, always obsolete. Minimum flow is to be determined on the landscape level, i. e. from the annual mean natural flow at the diversion.

If you anyhow use a typical river section it is to be taken from an undamaged pristine river where the running water has done its work, where all energy is used to ventilate the river and create biological mass and diversity. But, it is still a very questionable exercise. In the damaged regulated river Surnas deep pools has been filled and there are little resting and winter habitat for salmon.

The power company Statkraft describes a small shallow section from Surna as typical in the revision document for the Folla-Vindöla Regulation. With this section they try to establish some truths.

1.      They describe water flow that salmon prefer but do not recognize that habitat deteriorate in the preferred flow but improve in a flood.

2.      They present a shallow and most damaged river section when little water is running to establish the section as typical or representative for Surna.

3.      The exercising calculations using the presented section are used to suggest nonexistent minimum flow of water.

4.      Statkraft will give the impression that a damaged river can’t be changed to a more natural one. This is not true, as well as a river can be damaged it can be repaired for natural processes. The best is to let the river do the work, to be more natural.

5.      The conclusion is that Statkraft does not approve of minimum water for biological diversity. Today there is an excess of electrical power and our assessment gives that a decrease of 10 % power generation is neglectable for the community but do a lot of good for Surnas biological diversity. A good salmon river pumps annually tens of millions kronor into the valley. However, the last 10 % power generation is probably used for bonus.

Back to the original question: Do representative river sections exist? No, they don’t.