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Increased growth and distribution of Ephemerella aurivillii (Ephemeroptera) after hydropower regulation of the Aurland catchment in Western Norway
Author(s) -
Raddum Gunnar G.,
Fjellheim Arne,
Velle Gaute
Publication year - 2008
Publication title -
river research and applications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.679
H-Index - 94
eISSN - 1535-1467
pISSN - 1535-1459
DOI - 10.1002/rra.1142
Subject(s) - hydropower , hydrology (agriculture) , drainage basin , environmental science , watershed , mayfly , larva , degree (music) , ecology , geography , biology , geology , physics , geotechnical engineering , cartography , machine learning , computer science , acoustics
The Aurland watershed has been regulated for hydropower since the establishment of a series of power plants during the period 1970–1983. This resulted in a strong reduction of the flow in the river Vassbygdelvi, the inlet river to lake Vassbygdvatn. In the downstream river Aurland, the flow has varied, but from 2000 the intention has been to simulate pre‐regulation winter flow as far as possible. The temperature in the river Vassbygdelvi has increased from about 1500 degree‐days per year before regulation to above 2000 degree‐days after regulation. In the river Aurland the thermal regime, expressed as degree‐days per year, was more or less unchanged, but a small reduction in the summer temperature and a corresponding increase during other periods was observed. The mayfly Ephemerella aurivillii (Bengtsson) was not recorded in Vassbygdelvi prior to regulation, but became abundant in the river after. Full‐grown larvae were recorded 1–2 months earlier in the river Vassbygdelvi than in the river Aurland after regulation. E. aurivillii has a 1‐year life cycle with imagos present in June–August. Young larvae occurred from June to early September. It is concluded that larvae of E. aurivillii could not complete their life cycle within 1 year before regulation in the river Vassbygdelvi, due to low temperature. The study demonstrates how temperature can regulate the distribution of a species with a strict 1‐year life cycle. Copyright © 2008 John Wiley & Sons, Ltd.