Managing and taking care of water areas is part of the duties of Metsähallitus. The public water areas owned by the Finnish State are controlled by Metsähallitus as of 1 January 2016. These waters include all territorial waters along the Finnish coastline as well as the main bodies of some of Finland's major lakes.
Metsähallitus has extensive experience in restoring streams and their drainage areas. This work has been conducted especially in the Iijoki River since 1998. These restoration efforts not only improve the habitats of fish species, but they also positively affect game habitats, biodiversity and the water economy of small running waters.
The Lake Kostonjärvi fish passage, a co-operation project in which Metsähallitus was involved, was completed in 2012, the same year the National Fish Passage Strategy came into effect.
Furthermore, Metsähallitus has created gravel spawning grounds in various river areas to facilitate the reproduction of trout and grayling.
As a result of forestry activity, both solid matter and nutrients can be washed into surrounding waterways. The pollution load can become very significant locally in the headwaters of waterways, especially in smaller waters. When these activities are carried out across a large surface area, the drainage area also grows exceptionally large and the simultaneously released masses of water can increase the load significantly. With careful planning these damages to the waterways can be crucially reduced, which also reduces the subsequent need for renovation investments. When planning forestry activities, it is key to recognise the parts of the terrain that are critical in terms of water pollution control (parts that are vulnerable to erosion). When done right, the amount of loose matter and the corrosive effect that the released water has on the soil can be minimised, which in turn reduces the need for water pollution control infrastructure downstream of the affected area.
A new geographic information system (RLGIS) allows us to model the flow of surface waters for each drainage area specifically. The system allows us to connect different factors that contribute to the pollution load, including the amounts of water running in the channels and the slope ratios and soil types in the terrain. The system makes use of topographical models and data on the area's ditches, waterways and fields (gleaned from the NLS Topographic Database, for example). The accuracy of the analysis can be increased even further if it is supported by a digital soil map. The RLGIS system models how the surface waters are distributed across the drainage area and what channels they use to flow into the downstream waterway. The model calculates the flow rate and erosion potential for each section of each ditch within the drainage area based on the size of each ditch's drainage area, the amount of water running in it, the slope ratio of the terrain (slope of the ditch) and the type of soil in the area. When all of the ditches within the drainage area have been classified and the vulnerable sections have been identified, the obtained data can be used not only to direct the tilling work, but also to plan restorative ditching efforts during the later stages.
The results of the analysis can also be made into charts and added to planning documents (see picture 126.96.36.199). With the help of this analysis, the ditches or sections of ditches with high erosion potential can be left entirely undug, for example, or the water can be directed to flow through other channels. The required water pollution control structures can also be placed and scaled more appropriately when the risks are known. A surface water analysis should always be included in the planning of restorative ditching efforts.
The method has been developed further to also make it useful in the planning of activities related to regeneration felling and the tillage of soil (see picture 4.5.4.b). The method makes it possible to estimate and predict the drainage channels of surface waters in the areas in question and then use this information to plan the required water pollution control structures and scale the pollution control zones proportionately to the affected waterway.