Pekka M. Rossi, Pertti Ala-aho, Bjørn Kløve
Eskers aquifers are common groundwater bodies in Europe. Management of these aquifers should account for the sustainability of groundwater dependent ecosystems and land use in an integrated way. To study the impacts of peatland ditches to esker aquifer, Rokua Esker aquifer case study site was studied with in situ methods and modeling. Rokua esker area contains groundwater-dependent lakes and a periodic water level decline has raised concerns about the future of these lakes. Peatland drainage in the vicinity of the aquifer has been accused of changing the aquifer conditions but the connection of the drainages and the aquifer has not been studied previously.
Based on in situ measurements, groundwater discharge from the esker aquifer to drained peatland was studied to identify relevant hydrological processes for groundwater-surface water interactions. The results revealed a connection between the aquifer and the peatland whereby groundwater can enter the ditches through seepage or preferential flow.
Modeling was used to determine critical factors in the management of the esker aquifer-peatland system. The results showed that climate and land use can affect esker groundwater, while peatland drainage in the vicinity can have similar impacts to groundwater abstraction and drought. Peatland restoration by filling in drainage ditches could possibly restore the aquifer groundwater levels. However, for the Rokua aquifer, which will possibly experience less severe dry periods in the future, extensive drainage restoration is currently too major, uncertain, and expensive a measure relative to the expected benefits.