Water quality and recreational and natural values of lakes and rivers

Takaisin raportteihin

5. Water quality and recreational and natural values of lakes and rivers

Lahti Environmental Services continued the maintenance of the Lake Vesijärvi and other small lakes as a part of the Vesijärvi program devised together with the Vesijärvi Foundation. Lahti Environmental Services was responsible e.g. for the management of fish stocks and oxygenation of Lake Vesijärvi and Lake Kymijärvi, water sampling in lakes and ditches, and the maintenance of ten automatic water quality monitoring stations. The fishing catch from Lake Vesijärvi and Lake Kymijärvi was total 140 tons, of which up to 65 tons could be utilized. Breams were delivered especially for raw material of fish steaks and roaches for preservatives. The River Caretaker project included repairs to the River Seestanjoki, improving the flow of its waters, as well as the introduction of a trout population to the river. A protective wetland area covering over two hectares was established in the Lake Sylvöjärvi delta. A preliminary report concerning the adjustment of lake water surface levels in the Nastola area was completed. During 2017, various reports were prepared relating to the condition of water bodies, to the environmental strain they bear as well as their populations of fish and other animals. Populations of eel and trout were introduced to Lake Vesijärvi, while pikeperch were introduced to the Lake Joutjärvi.

The implementation of storm water management is quided by the city’s storm water programme, and the application is governed by the Stormwater working group. Actions in stormwater project were implemented in Ranta-Kartano and Western Hennala areas. The project is funded by Ministry of Environment and it is a spearhead project of government programme in water and marine management.

In addition, an AIKO funding was applied and granted for the Hule Smart&Clean project coordinated by the City of Lahti, aiming to develop new ways of storm water quality management together with different cities, businesses and universities. Storm water quality is constantly monitored at two automatic monitoring stations in the Lake Vesijärvi area. Monitoring samples are also taken in the Lake Kymijärvi area and in Western Hennala, and a total of 55 samples were taken in 2017. 

Lake water chlorophyll a, measured in August (µg/L)

Vesijärvi, Lankiluoto in Enonselkä basin5,86,84,8252211131112764,51413168,7101212
Hollola, Lake Arkiomaanjärvi3,72,97,34,46,75,74,63,254,9
Nastola, Lake Salajärvi8,1917317,41312111015149,58,18,98,4


Peak in 2009 is due to abundant blue-green algal bloom at the measuring moment.








Lake water transparency measured in August (m)

Vesijärvi, Enonselkä basin2,81,92,02,92,32,21,82,11,80,92,22,31,81,81,7222,5
Lake Alasenjärvi4,62,53,33,33,03,13,02,52,53,03,53,22,03,043
Hollola, Lake Arkiomaanjärvi2,02,02,02,42,01,82,02,52,3
Nastola, Lake Salajärvi1,52,02,53,02,02,01,811,6







Lake Vesijärvi management fishing catch (tonnes/year)



Kymijärvi power plant’s heating load into Lake Vesijärvi (TJ)



Percentage of lakes in good or excellent condition (% of total lake surface area)




Future plans and challenges:
• Reducing the external and internal load on Lake Vesijärvi.
• A rehabilitation method for cutting down the internal load will be planned for the Lake Kymijärvi.
• Achieving the target levels outlined in the Water Framework Directive for all lakes.
• Decreasing the storm water load of Lahti city centre.
• Reducing the adverse effects caused by the excessive fluctuation of the water level of the lakes in the former Nastola area.



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