THE ARTIFICIAL RECHARGE PROJECT OF THE VIRTTAANKANGAS AQUIFER, SOUTHWESTERN FINLAND

Insufficient water reserves during dry periods and seasonal quality problems in raw water have created the need to replace the water supply for the Turku region, southwestern Finland from the local surface sources with artificially recharged groundwater. The artificial recharge will be conducted in the Quaternary esker aquifer called the Virttaankangas aquifer, located 66 km north of Turku. The water for the infiltration will be extracted from the River Kokemäenjoki, located 28 km north of Virttaankangas. A total amount of 1.3 m³s^-1 of artificially recharged groundwater will be delivered for consumption to the 285,000 inhabitants in the Turku region by the end of this decade.

A project of this scale needs a solid basis of information for the planning and implementation of the artificial recharge. The various geologic features of the aquifer affecting the flow of the infiltrated water needed to be mapped and characterized in detail. The first three-dimensional (3-D) geologic model of the Virttaankangas area was completed in 2001. Since then, various updates and extensions have been introduced to the 3-D model.

The 3-D geologic modeling studies have required a flexible database capable of storing and analyzing the 3-D data. As the amount of data has increased on a daily basis, several routine tasks have been automated to save time and reduce human errors. These procedures include the preparation of input data for the groundwater flow model, which is integrated with the existing 3-D geological model.

The database and the 3-D modeling tools are key for understanding the internal structures and variation of the geologic materials of the Virttaankangas aquifer, both of which affect the ability of the aquifer to recharge and discharge water. Therefore, these modeling tools are crucial for evaluating and controlling the effects, and the long-term success, of the planned artificial recharge project in the Virttaankangas aquifer area.