Holocene groundwater table fluctuations in a small perched aquifer inferred from sediment record of Kankaanjärvi, SW Finland

Kankaanjarvi is a closed seepage lake controlled by groundwater flow within a perched aquifer. The results of this study indicate that its paleolimnological record forms a detailed groundwater table proxy covering the Holocene. Lake-level fluctuations were reconstructed from AMS-dated shifts in sediment properties, indicating marked natural changes of exceptional magnitude during the last 9000 years. The basin was more or less dry from 9000 to 6000 years ago. Since then, the water level gradually rose to its present limits of fluctuations about 3000 years ago. The record indicates that the water table of the associated perched aquifer is sensitive to precipitation changes, and that a decrease of 100 mm in annual precipitation may explain the low early Holocene level of the water system. The predicted climate change will likely keep the water table at a high, but stable level due to increased precipitation rates.