1.10.2015

Kivisalmi pumping station has been operational for slightly over seven months. The preliminary results have been promising.

The Kivisalmi pumping station has been operational for slightly over seven months. The preliminary results have been promising.

In August 2015, the nutrient concentrations had decreased somewhat from the previous year’s end-of-summer levels and the oxygen concentration level was also good. The results are preliminary, but promising.

”There may be significant variation from year to year; major conclusions cannot be made on the basis of one year’s results, but we are heading in the right direction and the results are encouraging,” says Project Coordinator Raija Aura.

The ice breakup came early this year, in April, so the open water season started exceptionally early. In particular, the beginning of the summer was chilly and the water temperature rose slowly and steadily, throughout the water mass. Typical temperature-based stratification was nearly undetected in several of the sampling points. Strong stratification of water often causes oxygen deficiency and increased concentrations of nutrients and other pollutants in late summer in the bottom water layers near the lake bed. In the absence of stratification, the oxygen levels remained good all through the summer and water quality was steady throughout the water mass. Only at the 15-metre sample point in the mid-lake area of Vehkasalonselkä was slight stratification detected in the water and minor oxygen deficiency in the bottom water.

Early summer was chilly and rainy. Rainfall increases run-off and loading to the water body, which is a sign of deteriorating water quality. And in fact the waters of Pien-Saimaa were turbid at several sampling points in early summer. During the summer, however, the water became less turbid. There were no significant changes in COD (chemical oxygen demand), which expresses the amount of organic compounds in the water. However, there was slightly more colour in the surface water compared to the previous year.

Only a few blue-green algae observations were made during the summer. In mid-September, there were abundant blue-green algae blooms in various places in the Pien-Saimaa water bodies for a couple of weeks.

The Kivisalmi pumping station located at Lappeenranta’s Kivisalmi inlet pushes water from the mid-lake area of Vehkasalonselkä to another mid-lake area, Piiluvanselkä, at the rate of 10 m3/s. On the eastern side of Taipalsaarentie road, the waters of Pien-Saimaa have fewer nutrients and they are clearer but of a darker colour compared to the waters of Pien-Saimaa on the western side of the same road. The purpose of the pumping station is to reduce the nutrient concentrations and algae blooms in the waters of Western Pien-Saimaa.

Monitoring of the pumping station began immediately after the pump was put into service in February 2015. From the beginning, monitoring was carried out at eight sampling points every other week. In the summer, monitoring was reduced by half – four sample points once a month. In addition, water quality is monitored through an automated measuring station in the mid-lake area of Piiluvanselkä.

Kivisalmi pumping station has been operational for slightly over seven months. The preliminary results have been promising.

Brochure: Purifying Pien-Saimaa by pumping