fulltext - DiVA

The J\1ajor Rivers of Northern SwedenBy NILS QUENNERSTEDTThe oldest known traces of human habitation inthe north of Sweden, dating some 5000 years back,are mostly located near its lakes and waterways.These waterways provided important channels ofcommunication and furnished a never-ending andeasily available supply of food in the form of fish.The first attempts at cultivation took place in thebroad valleys, bordering the largest rivers. Theirsediments provided good agricultural land, andthe verdant fringe areas, subjected to seasonalflooding, gave excellent grazing for the livestock.As development proceeded, salmon fishing becameof great economic importance and was subsequentlythe subject of much litigation. There are recordsof lawsuits, dating back to the Middle Ages, whichtell of the tug-of-war between Church, State andpeasantry regarding the ownership of fishing rightsand, even today, some 500 years later, such disputesare occasionally encountered.During the second half of the last century, whenthe timber industry began to assume large proportions,it was on the bosoms of these northern riversthat the logs were floated down to the sawmills.This was the manner in which the waterways werefirst harnessed in the service of industry. Alongthe less navigable stretches, the river beds werelevelled and troublesome boulders were removedin order to facilitate the passage of the floatingtimber. It was only in the smaller tributary systemsthat dams were constructed, in order to retain waterand to regulate the flow so as to coincide with thestart of the timber-floating season. These measurescaused no noticeable alteration in the normalseasonal water-levels further downstream, in thelarge rivers, as the relatively small volume ofimpounded water was usually released about thetime of spring flood or shortly after and made littledifference to the total flow.The subsequent utilization of the rivers for hydroelectricpurposes has radically changed existingnatural conditions in quite a different way. Unfortunately,these changes have been put into effectwithout a satisfactory study of cause and effect;in no case have adequate records been secured ofthe pre-existing hydrobiological conditions or theoriginal plant and animal ecology of the affectedareas. There is even an apparent danger that asatisfactory field survey will never be accomplishedin time, should the remaining free-running riversbe exploited too hastily.During the last two decades, a great many newhydro-electric plants have been built along severalof the North Swedish rivers. This intense activityin the north is explained by the fact that morethan 80 % of Sweden's potential turbine-effect(at mean water flow) is attrioutable to northcountryrivers. Moreover, the rivers of SouthSweden are now almost fully utilized.Of the twelve large northern main rivers, onlythree have not yet been changed out of recognitionthrough hydro-electric development. These three"virgin" rivers are: the Torne river which, with itstributary the Muonio river, marks the boundarybetween Sweden and Finland, the Kalix river andthe Pite river (about the two former, see PEKKARI'scontribution). Furthermore, the proposed developmenthas not yet commenced on the northern forkof the Ume river (the Vindel river; cf. WASSEN'spaper in this volume).Characteristic of the large rivers, which all havetheir sources in the mountains, is the existence of adiscontinuous gradient from source to estuary,resulting in numerous rapids and less frequentwaterfalls, interspersed with calmer stretches ofwater. Most of the catchment areas of these riverslie at a higher altitude than 300 metres above seaActa Phytogeogr. Suec. 50