Quantifying groundwater dependence of a sub-polar lake cluster in Finland using an isotope mass balance approach
A stable isotope study of 67 kettle lakes and ponds situated on an esker aquifer (90 km 2 ) in northern Finland was carried out to determine the role and extent of groundwater inflow in groundwater-dependent lakes. Distinct seasonal fluctuations in the δ 18 O and δ 2 H values of lakes are the result...
| Published in: | Hydrology and Earth System Sciences |
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| Main Authors: | , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Copernicus Publications
2015
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| Subjects: | |
| Online Access: | https://doi.org/10.5194/hess-19-1247-2015 https://doaj.org/article/bd186563dfa94603aa64648f359fef9d |
| Summary: | A stable isotope study of 67 kettle lakes and ponds situated on an esker aquifer (90 km 2 ) in northern Finland was carried out to determine the role and extent of groundwater inflow in groundwater-dependent lakes. Distinct seasonal fluctuations in the δ 18 O and δ 2 H values of lakes are the result of seasonal ice cover prohibiting evaporation during the winter. An iterative isotope mass balance approach was used to calculate the inflow-to-evaporation ratios ( I TOT / E ) of all 67 lakes during the summer of 2013 when the isotopic compositions of the lakes were approaching a steady-state. The balance calculations were carried out independently for 2 H and 18 O data. Since evaporation rates were derived independently of any mass balance considerations, it was possible to determine the total inflow ( I TOT ) and mean turnover time (MTT) of the lakes. Furthermore, the groundwater seepage rates to all studied lakes were calculated. A quantitative measure was introduced for the dependence of a lake on groundwater ( G index) that is defined as the percentage contribution of groundwater inflow to the total inflow of water to the given lake. The G index values of the lakes studied ranged from ca. 39 to 98%, revealing generally large groundwater dependency among the studied lakes. This study shows the effectiveness of applying an isotope mass balance approach to quantify the groundwater reliance of lakes situated in a relatively small area with similar climatic conditions. |
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