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

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

Lahti Environmental Services continued the maintenance of Lake Vesijärvi and smaller lakes as part of the Vesijärvi programme prepared together with the Vesijärvi Foundation. Lahti Environmental Services were responsible, among other things, for the management of fish stocks in the Vesijärvi and Kymijärvi lakes, oxygenation of Vesijärvi, water sampling in lakes and ditches, and the maintenance of ten automatic water quality monitoring stations. The management fishing catch from Vesijärvi and Kymijärvi totalled 129 tonnes, of which approximately 26.5 tonnes could be utilised. Bream was particularly used as raw material for fish steaks and roaches for the production of canned food. A permit application plan was prepared for stopping the regulation of Lake Iso-Kukkanen and for the restoration of the Kumianjoki river.

A rapids area on the Seestaanjoki river was restored. At the same time, a submerged dam at the head of the rapids was modified to enable fish to pass. After this, there are no known fish migration obstacles on the Seestaanjoki river.

A key project led by the University of Helsinki and funded by the Ministry of the Environment tested a novel application of hypolimnetic withdrawal in Lake Kymijärvi. Various reports were prepared in 2018 relating to the condition and loading of water bodies as well as their bottom feeder and fish populations. Populations of eel and trout were introduced to Lake Vesijärvi.

Storm water management is guided by the city’s storm water programme, and its application is co-ordinated by the city’s storm water working group. Measures related to the storm water key project were implemented in the Ranta-Kartano and Länsi-Hennala areas. This key project of the government programme for water and marine management is funded by the Ministry of the Environment. The AIKO-funded Hule Smart&Clean project, coordinated by the City of Lahti, developed new methods for storm water quality management in co-operation with cities, companies and universities. The quality of storm water was continuously monitored at two automatic monitoring stations in the Vesijärvi area.


2019 Lake water chlorophyll a, measured in August (µg/L)

Vesijärvi, Lankiluoto in Enonselkä basin5,86,84,8252211131112764,51413168,710121220
Hollola, Lake Arkiomaanjärvi3,72,97,34,46,75,74,63,25,04,94,8
Nastola, Lake Salajärvi8,1917317,41312111015149,58,18,98,47,9


2019 Lake water transparency measured in August (m)

Vesijärvi, Enonselkä basin2,81,92,02,92,32,21,82,11,80,92,22,31,81,81,722,02,51,8
Lake Alasenjärvi4,62,53,33,33,03,13,02,52,53,03,53,22,03,04,03,02,7
Hollola, Lake Arkiomaanjärvi2,02,02,02,42,01,82,02,52,32,0
Nastola, Lake Salajärvi1,52,02,53,02,02,01,81,01,62,3


2019 Lake Vesijärvi management fishing catch (tonnes/year)




2019 Kymijärvi power plant’s heating load into Lake Vesijärvi (TJ)

Heating load722508206111396661001107112468171293877,4600519278806



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

Good or excellent as the directive defines1111111111


Future plans and challenges
Reducing the external and internal load on Lake Vesijärvi.
Planning a rehabilitation method for cutting down the internal load on Lake Kymijärvi.
Achieving the target levels (good or excellent) 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 lakes in the Nastola area.




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