New method for quantifying groundwater dependency of a peatland

The Water Resources and Environmental Engineering Research Unit in the University of Oulu has developed a new method, based on the “heavy” stable isotopes of water, which makes it possible to quantify the amount of groundwater rising to peatland surface with only one areally extensive sampling.

The new isotope method has been tested in practice on a peatland, and researchers were surprised by the result: “The amount of groundwater in the peatland varied between 0 and 100 per cent. This is the first time that a peatland’s groundwater dependency has been quantified in different parts of the area. We were able to show that the hydrological connection of the various parts of the peatland to groundwater fluctuated greatly. There were groundwater-dependent areas both near a groundwater formation, and also farther away outside of the groundwater area limits”, says M.Sc. Elina Isokangas from the research group.

There is an ongoing inspection of the classification of groundwater areas in Finland, and their significant groundwater ecosystems are taken into consideration in the new E class. The new method now developed can be used in classifying peatland areas. “With this method, one sampling round during a non-rainy summer period can give a comprehensive picture of the role of groundwater in the peatland”, says Isokangas. There are over 6000 classified groundwater areas in Finland. They are important in the water supply of communities, as they produce over half of our drinking water. At the same time, groundwater pumping is threatening valuable springs and peatlands.

The law for waters maintenance and organization of sea maintenance obligates to classify and protect ecosystems that are directly dependent of groundwater. The problem in conservation has been how to observe the hydrological connection between a groundwater formation and a peatland in a way that is comprehensive enough but still cost-efficient. The new method now developed can be used in defining the groundwater connectivity in peatland ecosystems.

Previously, the evaluation of groundwater dependency had been made mostly based on vegetation analysis. However, vegetation reacts slowly to a changing hydrological situation, and thus the effects of groundwater pumping, for example, cannot be quickly observed.

This study is part of a larger dissertation research, in which Elina Isokangas is aiming to develop methods for defining groundwater dependence in other ecosystems as well, such as lakes and brooks.

The peatland isotope study ”Quantifying spatial groundwater dependence in peatlands through a distributed isotope mass balance approach” was published in Water Resources Research, which is the highest quality peer-reviewed magazine in hydrology. The research group members were, in addition to Elina Isokangas, Professor Bjørn Kløve, research doctors Pekka Rossi, Anna-Kaisa Ronkanen and Hannu Marttila, and the Polish isotope hydrology expert, Professor Kazimierz Rozanski.

Water Resources and Environmental Engineering Research Unit

Last updated: 27.9.2017