Bjoreio

{{Use mdy dates|date=October 2023}}

{{Infobox river

|name = Bjoreio

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|image = Vøringfossen.jpg

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|image_caption = Vøring Falls on the Bjoreio River

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|pushpin_map = Vestland#Norway

|pushpin_map_caption = Location of the river

|subdivision_type1 = Country

|subdivision_name1 = Norway

|subdivision_type2 = County

|subdivision_name2 = Vestland

|subdivision_type3 = Municipalities

|subdivision_name3 = Eidfjord Municipality

|length = {{convert|72|km|mi|abbr=on}}

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|source1 = Tinnhølen

|source1_location = Eidfjord, Norway

|source1_coordinates = {{coord|60.2865568|7.5624561|region:NO}}

|source1_elevation = {{convert|1213|m|sp=us|abbr=on}}

|mouth = Lake Eidfjord

|mouth_location = Eidfjord, Norway

|mouth_coordinates = {{coord|60.427569|7.1223271|display=inline,title}}

|mouth_elevation = {{convert|17.5|m|sp=us|abbr=on}}

|progression =

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|basin_size = {{convert|627|km2|sp=us|abbr=on}}

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The Bjoreio, also known as the Bjoreia,{{cite web|last1=Rosvold|first1=Knut A.|title=Sima kraftverk|url=https://snl.no/Sima_kraftverk|website=Store norske leksikon|accessdate=April 28, 2018}} is a river in the municipality of Eidfjord in Vestland, Norway.{{cite web|title=Bjoreia|url=https://snl.no/Bjoreia|website=Store norske leksikon|accessdate=April 28, 2018}}{{cite web|title=Bjoreio, Eidfjord (Hordaland)|url=https://www.yr.no/place/Norway/Hordaland/Eidfjord/Bjoreio/|website=Yr|publisher=Norwegian Meteorological Institute and the Norwegian Broadcasting Corporation|accessdate=April 28, 2018}}{{cite book|title=Bjoreio|date=1989|publisher=Miljøverndepartemetet|location=Oslo|isbn=82-7243-707-4|url=http://www.miljodirektoratet.no/old/uversjonert/Vassdragsrapporter/Samla%20Plan/Hordaland/222%20Bjoreio%2001%20Tveitafoss.pdf|accessdate=April 28, 2018}} The river is {{convert|72|km|sp=us}} long, and it has a drainage basin of {{convert|627|km2|sp=us}}. Its natural average discharge is {{convert|25.2|m3/s|sp=us}},{{cite web|title=Nedbørfelt (REGINE)|url=https://www.nve.no/karttjenester/kartdata/vassdragsdata/nedborfelt-regine/|accessdate=April 28, 2018}} but this is considerably less today because of hydroelectric infrastructure along the watercourse.

The Bjoreio has its origin on the northwest side of Sildabunutane, a {{convert|1444|m|sp=us|adj=on}} mountain in Hardangervidda National Park. The river, which is called the Eitro here, then runs southeast through Sildabudalen, a wide valley, and into Langavatnet, a lake at an elevation of {{convert|1223|m|sp=us}}. Under the name Snero the river continues the short distance to Tinnhølen, a lake at {{convert|1213|m|sp=us}}. When it flows out of Tinnhølen the river is now named Bjoreio, and it runs to the northwest out of the national park and down through the Bjorei Valley (Bjoreidalen). At the Nybu tourist lodge it is joined by the Svinto from the east. Here the river runs through the Bjorei Valley Nature Reserve (Bjoreidalen naturreservat). In the nature reserve there is a ban on walking outside specially marked trails from May 20 to July 20 to protect nesting birds.{{cite web|title=Bjoreidalen|url=http://faktaark.naturbase.no/Vern?id=VV00001054&srid=32633|website=Miljødirektoratet|accessdate=April 29, 2018}} Further downstream, at Storlia, is the {{convert|81|m|sp=us|adj=on}} high Sysen Dam, a large stone embankment that creates Lake Sysen on the Leiro River just before it empties into the Bjoreio. The rivers continues westward through the Sysen Valley, where its tributaries include the Isdølo from the north and the Drolstølbekken from the south. At Fossli the river creates {{convert|182|m|sp=us|adj=on}} high Vøring Falls, where it hurtles down into the narrow and deep Måbø Valley. The river empties into Lake Eidfjord in Øvre Eidfjord, only {{convert|500|m|sp=us}} from the nearby Veig River. At the opposite end of Lake Eidfjord, the short Eio River empties into the Hardanger Fjord.{{cite web|title=Bjoreio|url=http://norgeskart.no/#!/?zoom=9&lon=71308.02&lat=6718455.99&project=seeiendom&layers=1002,1015&sok=Bjoreio|website=Norgeskart|accessdate=April 29, 2018}}

Together with the nearby Sima River to the north, the Bjoreio River has been developed for power production at the Sima Hydroelectric Power Station.{{cite book|last1=Skoglund|first1=Helge|last2=Skår|first2=Bjørnar|last3=Gabrielsen|first3=Sven-Erik|last4=Barlaup|first4=Bjørn T.|title=Fiskebiologiske undersøkelser i Sima med vurdering av vintervannføring og stranding av gytegroper. 2011, 2012 og 2013|date=2013|publisher=LFI Uni Miljø|location=Bergen|url=https://uni.no/media/manual_upload/LFI_224.pdf|accessdate=April 28, 2018}} Lake Sysen is used as the main reservoir. The river's flow has been diverted through a tunnel to the lake and, together with the upper course of the Isdølo, the water is then directed to the power station below Kjeåsen on the north side of the Simadal Fjord. The river bed below the Sysen Dam is dry for most of the year, but during the summer season it is required to release water so that the flow at Vøring Falls is at least {{convert|12|m3/s|sp=us}}.

At the lower end of Lake Måbø (Måbøvatnet), the old road through the valley crosses the river over the Måbø Bridge.{{cite book|title=Nasjonal verneplan for veger, bruer og vegrelaterte kulturminner|date=2002|publisher=Vegdirektoratet|location=Oslo|page=170|url=https://www.vegvesen.no/_attachment/62326/binary/16316|accessdate=April 30, 2018}}