University of Oulu

Elina Isokangas, Anna-Kaisa Ronkanen, Pekka M. Rossi, Hannu Marttila, Bjørn Kløve, A tracer-based method for classifying groundwater dependence in boreal headwater streams, Journal of Hydrology, Volume 577, 2019, 123762, ISSN 0022-1694,

A tracer-based method for classifying groundwater dependence in boreal headwater streams

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Author: Isokangas, Elina1; Ronkanen, Anna-Kaisa1; Rossi, Pekka M.1;
Organizations: 1Water, Energy and Environmental Engineering Research Unit, Faculty of Technology, University of Oulu, P.O. Box 4300, FI-90014, Finland
Format: article
Version: accepted version
Access: open
Online Access: PDF Full Text (PDF, 2 MB)
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Language: English
Published: Elsevier, 2019
Publish Date: 2021-05-10


Ecosystem protection requires a better definition of groundwater (GW) dependence and tools to measure this dependence. In this study, a classification method for the GW dependence of headwater streams was devised based on the fact that GW affects discharge, thermal regime, and water quality. The method was tested in three boreal headwater streams discharging from two esker aquifers. Spatial and temporal variability of GW dependence were studied in the stream continuum at several locations, by combining continuous measurements of temperature, electrical conductivity, and discharge with discrete sampling of environmental tracers (e.g., stable water isotopes, silica, chloride). The stream tracer index method developed was used to classify stream sections into GW-dominated, GW-surface water (SW) transition, and SW-dominated zones. We found that, spatially, GW dependence along the stream varied widely, with calculated stream tracer index values ranging from 33 to 94%. The GW-dominated areas extended at least 745, 1 682, and 4 202 m downstream from the main GW discharge points in the three streams studied. A stream located in a pristine peatland-dominated catchment was more prone to rapid change from GW- to SW-dominated than two streams located in catchments dominated by peatland forestry. These results suggest that to evaluate the GW dependence of streams, it may be sufficient to sample stream sections only once, during summer low-flow conditions. The proposed method can serve as a water management tool, especially for streams of exceptional ecological importance or in places where anthropogenic activities are expected to change local hydrology and ecology.

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Series: Journal of hydrology
ISSN: 0022-1694
ISSN-E: 1879-2707
ISSN-L: 0022-1694
Volume: 577
Article number: 123762
DOI: 10.1016/j.jhydrol.2019.05.029
Type of Publication: A1 Journal article – refereed
Field of Science: 218 Environmental engineering
1171 Geosciences
Funding: This study was funded by the Academy of Finland (project no. 128377) and Renlund foundation.
Academy of Finland Grant Number: 128377
Detailed Information: 128377 (Academy of Finland Funding decision)
Copyright information: © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license