Quality and availability of groundwater

Takaisin raportteihin

4. Quality and availability of groundwater

vesiLahti and Hollola are located above the significant I Salpausselkä groundwater reserves. 2017 saw the commencement of construction work for the Lahti southern ring road, as well as the more detailed planning of the parts of the project carrying a considerable risk to the groundwater reserves. The project entails the lowering of groundwater surface level on the west side of Sokeritoppa by several metres from its natural level during construction. On this site, the groundwater surface level will be permanently lowered by approx. two metres. In the Liipola area, groundwater levels must be lowered by several metres due to tunnel construction, and the same applies to Patomäki. In order to minimize the risks to groundwater reserves, the project must be planned and implemented in close co-operation with the planners, Lahti Aqua as well as the various authorities concerned (Lahti Urban Environment service area, the Centre for Economic Development, Transport and the Environment, the Regional State Administrative Agencies).

In 2017, central Lahti implemented potassium and natrium formate as a replacement for de-icing salt in preventing slippery road surfaces. The impact of this change on groundwater quality will be monitored in the city centre over the coming years. The planning of joint monitoring of groundwater continued 2017 and preparation will carry on for the year 2018. Joint monitoring will commence in the Lahti groundwater area at the beginning of 2019.

The City of Lahti purchased the former Vientikerma water intake facility located in Asemantausta. Water intake ended when the facility ceased its operation, and at the same time the protective pumping of groundwater polluted by industrial cleaning activities stopped in the area. After the change of ownership, the water intake facility will be recommissioned for protective pumping, preventing the flowing of polluted groundwater from the area.

The water acquisition of Lahti and Hollola is solely based on groundwater reserves. The volume of water pumped for consumption in Lahti and Hollola totaled 25,000 m3 per day in 2017. All water samples taken met the quality requirements and recommendations set for household water. Approximately 100,000 m3 of groundwater is formed in the Lahti groundwater reserves every day, around four times the daily consumption.

The unmetered consumption percentage is as an indicator of the functionality and leakage rate of the water supply network. For all the water pumped in Lahti, the share of unmetered consumption was 7%, which is an excellent result at the national level, as the national average is around 20%. The unmetered consumption for the Hollola region was 12%. The lower the unmetered consumption rate, the smaller the amount of water, energy and chemicals going to waste.

Groundwater conductivity (μS/cm)

Indicates the total amount of salts dissolved in the water.
Sport Centre254235224221278216217230
Lahti Jalkaranta196202196205192175184186184183186
Hollola, Ruoppa1101051099711083106104106106107
Nastola, Mälkönen abstraction site172190215190220220200200210213220

Groundwater conductivity (μS/cm), depicts the total amount of salts dissolved in the water. Limit value is 2,500 µS/cm. Sport Centre water abstraction site hasn't been in production after 2007, because of the high amounts of pesticides. 




Atrazine levels in groundwater (μg/L)

Nastola Uusikylä (observation point GA1)2,91,310,82,63,2
Lahti (HP137, trakcside)1,62,22,31,21,80,30,3






Atrazine is a pesticide. Limit value for any particular pesticide in household water is 0.1 µg/L.








There were no major changes in water consumption during the year. The specific consumption figure includes water consumed by residents and the industry as well as loss caused by leakage. The figures for Lahti include Nastola and the figures for Hollola include Hämeenkoski.

Groundwater areas classified as being in poor state, %

Lahti and Hollola014142020151515282929292626


Water consumption (L/resident)

Lahti specific consumption197189184183179187181
Hollola specific consumption114113113110102120120
Nastola specific consumption212192211211216
Lahti household consumption127125124122121120119


Future plans and challenges:
• The need for water supply network renovations will increase as the pipelines built in the city’s years of rapid growth in the 1960s and 1970s will reach the end of their lifecycle.
• The construction of a motorway in the groundwater reserve area, and the resulting risks with lowering groundwater surface levels (highway 12).
• The regional preparation and implementation of the groundwater joint monitoring program.
• Monitoring the impact of the new de-icing method on the chloride levels in groundwater (observation point 126 central hospital).




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