WATER RESOURCES IN FINLAND – WATER QUALITY IN FINLAND

JYRKI RÖPELINENDoctor.Tech. (Civil Engineering)

Hydraulic and Geotechnical Engineeeringjyrki.ropelinen@oamk.fi

CONTENTS OF THE PRESENTATION

Water resources in Finland

Water quality, changes in quality

Lake restoration, reasons for restoration

Methods to lake restoration

External loading, methods to prevent loading

Recreational use; swimming, fishing, boating, summer cottage

SURFACE WATERS

Finland is rich in surface waters, with a total of 187,888 lakes and ponds larger than 500 square metres. The number of lakes larger than 1 ha (10 000 square metres) is estimated to be around 56 000. The total shoreline length of the lakes is 130 000 km. The total length of all rivers is estimated to be around 25 000 km. Almost a tenth of the country‘s total land area is covered by water. The total length of the coastlines of the Baltic Sea in the west and the south is 46,000 kilometres when the shorelines of islands are included.

In the Finnish Lake District (see map), a typical value is 40 lakes within 100 square kilometres.

There are three lakes larger than 1 000 square kilometres in Finland: Saimaa, Inari and Päijänne.

The annual variation of lake area is around 2 350 square kilometres and the annual variation of volume around 39,5 cubic kilometers.

Although there is plenty of water visible on the surface, most of these waters are not very deep.  Finland’s lakes contain a total of only 235 cubic kilometres of water – the same amount of water that flows through the Amazon in just two weeks. Finland’s lakes and coastal waters are so shallow because the rocks in this geologically stable region of Europe have been gradually evened out by erosion over millions of years, and during successive recent ice ages.

Finland’s shallow lakes are easily contaminated by pollution. Even relatively low concentrations of excess nutrients, acidic deposition or other harmful contaminants can easily disrupt their sensitive aquatic ecosystems.

Harmful pollutants also eventually run down through lakes and rivers into the sea. Finland lies almost entirely within the catchment area of the Baltic Sea, although rivers and streams in northernmost Finnish Lapland and parts of north-eastern Finland flow into the Barents Sea and the White Sea.

The Baltic Sea is also shallow, and sensitive to pollution. The Baltic is virtually an inland sea, and is burdened by exceptionally heavy loads of contaminants originating from its extensive catchment area, which is home to more than 80 million people .

The concentrations of inorganic substances in Finnish surface waters are low.

By contrast, the concentrations of dissolved organic substances, for example, humic acids, can be high locally, since bogs cover about 30% of the area of the country. The shallowness of lakes (average depth about 7 metres) and relatively low discharges of rivers, together with the long period of ice cover, make inland waters sensitive to pollution.

The water quality of Finnish inland waters improves from south to north and from west to east, being poorest in coastal areas in the south, southwest and west.

GROUNDWATER

Groundwater forms wherever water flows or trickles down into gaps, cracks, holes and pores within soils or rocks. Finland’s groundwater reserves are replenished in the spring when the winter snow and ice melts, and then often again in the autumn – typically the rainiest season.

Groundwater can be found in almost every part of Finland, but is particularly widespread in areas with extensive deposits of permeable sands and gravels formed during the last ice age. The depth of the water table may vary from less than a metre to more than thirty metres, but is typically about 2–5 metres below ground level.

In Finland, groundwater is widely used by local residents and by waterworks, since it is often much purer and better protected from contamination than the water in lakes and rivers. Groundwater can usually be safely consumed without any treatment.

Approximately 60% of the total water supply distributed by Finland’s waterworks consists of groundwater.

Threats

Groundwater reserves in Finland do not normally suffer from contamination on a wider scale, since individual bodies of groundwater tend to be small. The risk of contamination is highest in areas where soils consist of coarser sands and gravels, which can be infiltrated by pollutants as well as water.

Considerable contamination may be caused locally where salts are used to de-ice slippery roads, on over-fertilised farmland, at garages and service stations where oils may accidentally enter the soil, and following accidents involving chemicals.

Groundwater quality may also be reduced by the nature of the local soil or bedrock. In certain areas the groundwater can contain harmful concentrations of iron and manganese. Wells drilled into the bedrock may contain high levels of substances such as arsenic or radon in places.

 HYDROLOGY IN FINLAND

During the period 1961-1990, the Finnish territory received a mean precipitation of 660 mm. Of this amount, 341 mm was evaporated, while 318 mm flowed into the seas. The water storage was increased by 1 mm during this period. The mentioned value 318 mm corresponds to a mean discharge of 3400 m3/s.

There is rather good data on the Finnish water resources meaning the presently available total amount of surface water and groundwater. Of the most important phases of the water circulation, some records of precipitation and runoff (discharge) began already in the 19th century.

Finland belongs to the so called humid zone; the major water bodies do not normally dry out. A typical feature in Finland is the abundance of water bodies - lakes and rivers. The water situation may, however, greatly differ from year to year. Within a year, there is a considerable difference between the winter (when the precipitation is stored in the snow cover) and the summer (when a major part of the rainwater evaporates).

The waters are in Southern Finland least abundant in early autumn, in Northern Finland in late winter. An trend towards more abundant precipitation has increased the wintertime discharges and water levels in the coastal areas, while the snow cover has increased in the eastern and northern parts of the country.

River basin districtsMainland Finland is divided into five river basin districts (RBD) for the purposes of the river basin planning and management required under the EU Water Framework Directive (WFD). These districts have been

defined on the basis of the natural basins of major rivers:

1. Vuoksi River Basin District2. Kymijoki-Gulf of Finland River Basin District3. Kokemäenjoki-Archipelago Sea-Bothnian Sea River Basin District4. Oulujoki-Iijoki River Basin District5. Kemijoki River Basin District

Two international river basin districts (IRBD) have also been designated covering parts of Finland:

6. Tornionjoki IRBD (shared with Sweden)7. Teno, Näätämöjoki and Paatsjoki IRBD (shared with Norway)8. A separate RBD has been defined to cover the autonomous Åland Islands province, where the WFD is being implemented by the provincial government

WATER QUALITY CLASSIFICATION

 

The general usability classification of water bodies gives an idea about the average suitability of water bodies for water supply, fishing and recreation (swimming, fishing etc.) in Finland.

The quality class is determined based on the natural quality of the water and human impacts. The water bodies have been classified into five classes: excellent, good, satisfactory, passable and poor.

The latest classification based on data from 2000-2003 covered 82% of the total area of lakes with size greater than one square kilometre, 16% of the total length of rivers with width more than two metres, and the sea area inside the Finnish territorial waters.

Class

Class interpretation Variables and their threshold values

IExcellent

The watercourse is in a natural state, usually oligotrophic, clear or with some humus. Water use is not restricted by any special occurrence of algae.Highly suitable for all modes of use.

·                       colour < 50 mg Pt/l ·                       transparency > 2.5 m ·                       turbidity < 1.5 FTU ·                       fecal coliforms or fecal streptococci < 10 CFU/100 ml ·                       total phosphorus < 12 µg/l ·                       mean chlorophyll-a in the growing season < 4 µg/l(in Baltic Sea < 2 µg/l)  

IIGood

The watercourse is in a near-natural state, slightly eutrophic or clearly humic. Locally restricted algal blooms can occur occasionally. Water is still suitable for most modes of use.

·                       oxygen concentration in epilimnion 80–110% ·                       no oxygen defiency in the hypolimnion ·                       colour 50–100 mg Pt/l(< 200 in natural humic waters) ·                       transparency 1–2.5 m ·                       turbidity > 1.5 FTU ·                       feacal indicator bacteria< 50 CFU/100 ml ·                       total phosphorus < 30 µg/l(in Baltic Sea 12–20 µg/l ·                       mean chlorophyll-a in the growing season < 10 µg/l(in Baltic Sea < 2–4 µg/l)  

Criteria for the general water quality classification in Finland

IIISatisfactory

The watercourse is slightly affected by wastewaters, diffuse loading or other changing activity, or is appreciably eutrophic or humic due to natural causes. Algal blooms can occur repeatedly. Concentrations of harmful substances in water, sediment or biota can be slightly higher than in pristine conditions.The watercourse is usually satisfactory for most modes of use.

·                       oxygen concentration in epilimnion 70–120% ·                       some oxygen defiency may occur in the hypolimnion ·                       colour < 150 mg Pt/l ·                       transparency < 1 m ·                       feacal indicator bacteria< 100 CFU/100 m ·                       total phosphorus < 50 µg/l(in Baltic Sea 20–40 µg/l) ·                       mean chlorophyll-a in the growing season < 20 µg/l(in Baltic Sea 4–12 µg/l)  

IVPassable

The watercourse is strongly affected by wastewaters, diffuse loading or some other changing activity. Algal blooms are common and may restrict water use for a long period. Concentrations of harmful substances in water, sediment or biota can be clearly higher than in pristine conditions. In catchments with Littorina Sea* clay deposits, the pH of water can be very low for short periods and die-offs of fish caused by the acidic conditions can sometimes occur.Water is suitable only for modes of use having few water quality requirements.

·                       oxygen concentration in epilimnion 40–150%, frequent oxygen deficiency in the hypolimnion ·                       feacal indicator bacteria< 1 000 CFU/100 ml ·                       total phosphorus 50–100 µg/l(In Baltic Sea 40–80 µg/l) ·                       mean chlorophyll-a in the growing season 20–50 µg/l(In Baltic Sea 12–30 µg/l) ·                       algal blooms common ·                       concentrations of harmful substances:As < 50 µg/l, Hg < 2 µg/l, Cd < 5 µg/l, Cr < 50 µg/l, Pb < 50 µg/l, total cyanide < 50 µg/l ·                       off-flavours often found in fish  

VPoor

Wastewaters, diffuse loading or other changing activity extensively pollute the watercourse. Algal blooms occur frequently and are often abundant, restricting water use for a long period. Oxygen concentrations are clearly affected by eutrophication. Concentrations of harmful substances in water, sediment or biota can be at levels that cause a clear risk to the use of water or biota. In catchments with Littorina Sea* clay deposits, the pH of water can be very low for long periods and die-offs of fish caused by the acidic conditions occur repeatedly.Poorly suited to any mode of use.

·                       major problems of oxygen balance, oxygen saturation in the epilimnion during summer may exceed 150%; on the other hand total oxygen depletion at the surface may occur; at the end of the stratification season the whole hypolimnion may be anaerobic ·                       feacal indicator bacteria>1 000 CFU/100 ml ·                       total phosphorus > 100 µg/l(In Baltic Sea > 80 µg/l) ·                       mean chlorophyll-a in the growing season > 50 µg/l(In Baltic Sea > 30 µg/l) ·                       one or more of the following exceeds the threshold-limit specific for class IV: As, Hg, Cd, Cr, Pb or total cyanide ·                       mercury concentration in predatory fish species > 1 mg/kg ·                       oil film on the water surface often observed  

Map of the Water Quality in 2003 

Water quality mostly good in lakes and the open sea

 

The quality of water was excellent or good in 80% of the classified lake area and in the 73% of the sea area. In general, the water quality in rivers was worse than in lakes, because of human activities, such as agriculture are concentrated along rivers. Moreover, many rivers are sensitive to the effects of nutrient loading because of their low flow rates. Some 43% of rivers are classified as excellent or good quality. These rivers are mostly located in Northern Finland.

Comparison of classifications in 1984-2003

In Finland water quality has been classified since the 1970s. Using the same criteria, the environmental authorities have carried out the classification procedure four times for inland waters and twice for sea areas.

In the vicinity of towns and industrial plants, water quality had improved considerably already at the beginning of the 1990s, because of long-term measures for water protection. These measures were further improved during the 1990s..

Eutrophication is still a problem in coastal waters and the total area of these waters classified as passable or poor has increased. 

Changes in the water quality classes

 The two latest classifications, in the mid-1990s and at the beginning of the 2000s, have been compared on the next map.

The quality class wasimproved in 1220 km2 of lakes, 822 km of rivers and 890 km2 of sea area. At the same time, there was a deterioration in water quality in 690 km2 of lakes, 960 km of rivers and 10 450 km2 of sea area

LAKES

There has been little change in the water quality classifications of lakes. The clearest change occurred between the middle of the 1980s and the beginning of the 1990s. The main reason for this was the improvement in water quality in the vicinity of industrial plants and towns, where water protection measurements were very effective.

RIVERS

Changes in river water quality have been more detectable. The total figure for the two best classes, excellent and good, was slightly lower at the beginning of the 1990s than in the middle of the 1980s and now, at the beginning of the 2000s. At the same time, the total figure for the two worst classes, passable and bad, was slightly higher at the beginning of the 2000s than earlier. The reason for this could be, for example, changes in the volume of water in these periods or changes in the amount of water quality data available for classification.

SEA AREA

In sea areas, there are only two classifications that can be compared. The water quality in the Gulf of Finland has deteriorated from good to satisfactory. Eutrophication is a problem especially in the Gulf of Finland and in the vicinity some estuarites in the Gulf of Bothnia.

In the Gulf of Finland, eutrophication is a consequence of excessive nutrient loads and the special physical conditions of the sea area. The nutrient load has actually decreased by nearly 40% since the late 1980s. However, eutrophication continues to be a problem and is causing more abundant blue-green algae blooms in the summertime. The reason is that eutrophication is not only caused by nutrients loads from land areas, but also the release of phosphorus from the sea bottom sediment. The release of phosphorus from the sediments has increased because of the lack of oxygen on the sea bottom. This internal phosphorus loading is a problem also in many lakes in Finland.