Observations on groundwater‐surface water interactions at River Vantaa, Finland

The purpose of this paper is to emphasize the importance of groundwater‐surface water interaction when studying, modeling and assessing climate change impacts on river water management.

The investigations were focused on River Vantaa and its tributaries in southern Finland. The main methods used involved aerial infrared photography, thermal profiling of river sediments, water quality measurements, isotopic composition of oxygen and hydrogen δ¹⁸O, δ²H and river water temperature measurements. The authors present the first results of the field measurements targeted to identify the groundwater recharge and discharge zones within the river system.

Groundwater discharge zones were found to have a significant impact on water quality and volume in River Vantaa and its tributaries. In the drainage basin, the aerial infrared photography seemed to be a feasible and cost‐effective method to identify areas of groundwater discharge across the entire river basin. Around 350 groundwater/surface water interaction sites along the 220 km river system could be identified.

The interaction sites identified during the season of low flow rate should be considered as potential risk areas because during flood periods groundwater quality might be at risk due to bank infiltration. This should be considered in river basin management within predicted changing climatic conditions.

This is the first attempt in Finland to map systematically groundwater and river water interactions. The focus of the paper is relevant, because according to the existing climate scenarios, flooding of the main rivers in Finland will be more frequent in future, increasing the probability of groundwater‐surface water interaction.