THREE-DIMENSIONAL GEOLOGIC MODELING FOR GROUNDWATER AND LAND USE MANAGEMENT

Three-dimensional (3-D) geologic modeling was undertaken in the Virttaankangas aquifer area in southwestern Finland. This Late-Weichselian (Wisconsin Episode) interlobate esker aquifer is hosting one of the largest groundwater reserves in Finland. The aquifer is planned to be used to produce an artificially recharged groundwater reserve for the use of 285,000 inhabitants in the Turku region by infiltrating river water into the aquifer.

Hydrogeological features of the study area include a perched groundwater table as well as unconfined and confined aquifers that are connected with each other. The confined aquifer underlying glacial and postglacial silt and clay deposits comprises one of the Finland’s largest artesian groundwater areas. The accommodation of the artificial infiltration project with the complex hydrogeological environment creates a need to map and visualize the three-dimensional geological architecture and hydrogeological features of the area.

The results obtained from the earlier 3-D model pointed out the areas requiring further studies. At present, the study area has been enlarged from the earlier 3-D model area (Artimo 2003) to 80 km² to better cover the outskirts of the aquifer including the confined parts of the aquifer. The results of this ongoing study are to be used to support the groundwater and land use management in the area and to examine the effects of the artificial infiltration into the Virttaankangas esker aquifer. The recent 3-D geological model will be integrated with the future groundwater flow model(s) of the Virttaankangas area.

The 3-D geological model will be used as a tool for depicting the geological structures to a great variety of people with different interests, including scientists, municipal decision makers as well as local farmers, whose water supply is dependent on the good quality artesian groundwater.