University of Oulu

Alireza Gohari et al 2022 Environ. Res. Lett. 17 124027,

A century of variations in extreme flow across Finnish rivers

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Author: Gohari, Alireza1; Shahrood, Abolfazl Jalali2; Ghadimi, Sahand2;
Organizations: 1Department of Irrigation, College of Agriculture, Isfahan University of Technology, Isfahan 84156-83111, Iran
2Water, Energy, and Environmental Engineering Research Unit, University of Oulu, P.O. Box 4300, FIN-90014, Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.1 MB)
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Language: English
Published: IOP Publishing, 2022
Publish Date: 2023-01-04


River flow in cold climates is known to be one of the hydrological systems most affected by climate change, playing a central role in the sustainability of downstream socio-ecological systems. Numerous studies on the temporal and spatial variations of streamflow characteristics have been done, and a comprehensive study on the variation of hydrologic extremes is becoming increasingly important. This study evaluated the long-running changes in the magnitude, time, and inter-annual variability of hydrologic extremes, including high and low flow in 16 major Finnish rivers. We applied four new hydrologic extreme indices for summer–winter low flow ratio, spring-absolute high flow ratio, time-to-peak index, and increasing rate index during the snowmelt period to analyze the spatiotemporal variations of extreme streamflow from 1911 to 2020. The most detected trends in flow regimes have started in the last six decades and become more severe from 1991 to 2020, which is likely to be dominated by anthropogenic global warming. The results also indicated that alteration of low pulses in most rivers was associated with an increase (decrease) in winter (summer) flows, suggesting the annual minimum flow in summer frequently contradicts natural hydrologic regimes in Arctic rivers. Southern Finland has experienced higher variations in extreme hydrology over the last century. A new low flow regime was detected for southern rivers, characterized by frequent annual minimum flow in summer instead of winter. Moreover, the annual maximum flow before/after spring dictated a new high-flow regime characterized by frequent double peak flows in this region.

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Series: Environmental research letters
ISSN: 1748-9318
ISSN-E: 1748-9326
ISSN-L: 1748-9326
Volume: 17
Issue: 12
Article number: 124027
DOI: 10.1088/1748-9326/aca554
Type of Publication: A1 Journal article – refereed
Field of Science: 1171 Geosciences
218 Environmental engineering
112 Statistics and probability
Copyright information: © 2022 The Author(s). Published by IOP Publishing Ltd. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.