Estimating groundwater recharge in Finland

The Geological Survey of Finland (GTK) joined the GeoERA projects with two main objectives: firstly, to carry out meaningful scientific research in the groundwater and climate change sectors, and secondly, to network with other Eurogeosurveys. After a very good start, networking got a new twist, unfortunately, we all know why. However, colleagues from all over Europe feel to have become even more familiar by Zoom and other video calls. Perhaps we feel closer because of the glimpses to our personal livingrooms, bedrooms, hallways and wherever we have set our laptops at home, and the fact that we are facing similar challenges all over the globe.

Researchwise, we wanted to study groundwater formation, – resources and also threats to groundwater from nationwide perspective. Groundwater resources in Finland are mainly in quaternary sediments on top of crystalline bedrock. Retreating ice during the end of last deglaciation formed glaciofluvial eskers, which are now our main aquifers and conduits in large part of Scandinavia. Water is relatively easy to extract, but also vulnerable to multiple actions in current society. Changing climate is obviously a serious threat with droughts and storms being more unpredictable. Shallow groundwater is first in line to reflect changes in different circumstances.

In TACTIC our goal was to make simple, data based approach of potential groundwater recharge in Finland. From daily precipitation and temperature data we got estimation of evaporation and effective precipitation for years 1981-2010. We multiplied this with infiltration coefficients derived from surficial geology. This provided first round estimation of potential infiltration of groundwater. We compared these results with estimated and observed discharge data of aquifers. This comparison provided calibration coefficients for 13 sub-areas in Finland. Calibration coefficients reflect variating conditions of snow and frozen ground throughout the northern country. Finally, as a result, we have created a potential groundwater recharge Map of Finland, which is yet unpublished.

<– Figure 1. Sediment deposition in front of ice margin.

Figure 2. Potential groundwater recharge in Finland –>

Weather data is open data courtesy of Finnish Meteorological Institute (FMI), groundwater discharge data courtesy of Finnish Environment Institutes (SYKE) and geological data courtesy of Geological Survey of Finland (GTK). Ideas and guidelines owe to Geological Survey of Ireland (GSI)and Geological Survey of Sweden (SGU)