ABSTRACT
The stable isotopic composition of two rivers, the Vantaanjoki River and the Kokemäenjoki River, in southern and southwestern Finland was studied to resolve the transit times and travel routes of the river water in the two different catchments. The Kokemäenjoki River is dominated by great lake basins whereas the Vantaanjoki River has been reported having a significant groundwater component. The mean residence time of the young surface flow component could be resolved by sine function fitting onto the annual fluctuations of the isotopic signal, and the amount of base flow was estimated by using the isotopic composition of the river and groundwater. In this study, we found that the methods work for simple two component catchments. In more complex cases with three different components mixing, the solution becomes increasingly difficult and requires more study.
Acknowledgements
The authors would like to thank Heli Vahtera and other staff of The Water Protection Association of the River Vantaa and Helsinki Region for help in sampling, and the laboratory staff at the Geological Survey of Finland for their work. The authors would also like to acknowledge Turku Region Waterworks Ltd. for providing the data for the Kokemäenjoki River, and TAVASE OY for providing the lake water data. Tobias Fusswinkel is thanked for conversations regarding the topic, and the two anonymous reviewers for their insightful comments which helped improve the manuscript.
Disclosure statement
No potential conflict of interest was reported by the authors.
Notes
† Originally presented at the IAEA International Symposium on Isotope Hydrology: Revisiting Foundations and Exploring Frontiers, 11–15 May 2015, Vienna, Austria.