The Seven Biggest Rivers

Introduction

These seven rivers were chosen, because they have the largest drainage areas and the highest flow of the Baltic rivers. They cover 50% of the Baltic Sea catchment and all of them are transboundary rivers (Map 1.). They comprise nearly half (46%) of the total flow and over 50% of the nutrient inputs into the Baltic Sea (HELCOM PLC 5.5 report) so they have an important role in the inputs of the Baltic Sea. The human pressure is the highest in southern parts of the catchment with the most dense population and intensive agricultural activities.

Map 1. The catchment areas of the seven biggest rivers of the Baltic Sea catchment.

The Göta River

Figure 1. The drainage area (green line) of the Göta River.

Basic information

The area of the Göta River’s drainage basin is 50,200 km2. Most of the catchment belongs to Sweden, but the northernmost part is in Norway (Figure 1). The northern parts are pristine, whereas the human impact is most evident in southern parts of the catchment. Lake Vänern has an import role in the nutrient export as it efficiently retains nutrients originating from its upstream catchment.

Mean water flow: 698 m3 s-1

Area specific P inputs 8.0 kg km-2

Area specific N inputs 286 kg km-2

Trends in the export: The Göta River

In 2014 flow was 17% higher than the long term average flow. The N export was 14,000 t and P export 403 t.

N export decreased from 1995 to 2014 (Figure 1a).

There was a better correlation between flow and N export than with P export and flow (Figure 2b).

Figure 2a. Total N (green bars), total P export (blue bars) and flow (red line) by the Göta River from 1995 to 2014. The black lines are showing flow-normalised nutrient export and the green dashed lines the trend in the flow-normalised export.

y = 23.263x + 818.83R² = 0.7915

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y = 0.5249x + 41.347R² = 0.6229

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Figure 2b. The relationship between water flow and NTOT & PTOT export.

The Kemi River

Figure 3. The drainage area (green line) of the Kemi River.

Basic information

The River Kemi with its 550 km is the longest river in Finland and it flows in to the Bothnian Bay. It is draining the northern parts of Finland and small part of its catchment is in Russian territory. The river has been heavily used for hydroelectric production and the first dam was built in 1946. Today the total number of hydroelectric plants is 21. In addition to dams, two large reservoirs were built in the late 1960s in the northern parts of the catchment for hydroelectric purposes.

Forests cover over half and peatlands one fourth of the area. Especially the northernmost parts of the catchment area are in pristine conditions. Human impact, beside hydroelectric production, is mainly due to forestry practices. In addition, there are also nearly 20 peat production areas and three mines, but no other industrial activities causing pollution since the closure of the pulp factory in Kemijärvi in 2008. The largest city in the area is Rovaniemi with 62,000 inhabitants. Most of the cultivated areas and major part of the settlements are located in the lower parts of the catchment. Agricultural land areas and urban areas cover together less than 2% of the total catchment area and the population density is only two people per km2.

Mean water flow: 549 m3 s-1

Area specific P inputs 4.0 kg km-2

Area specific N inputs 127 kg km-2

Trends in the export: The Kemi River

In 2014 flow was 11% lower than the long term average flow. N export 5,670 t and P export 262 t.

No statistically significant trends could be detected (Figure 4a).

There was a good correlation between flow and nutrient export (Figure 4b).

Figure 4a. Total N (green bars), total P export (blue bars) and flow (red line) by the Kemi River from 1995 to 2014. The black lines are showing flow-normalised nutrient export and the green dashed lines the trend in the flow-normalised export.

y = 0.8445x - 144.09R² = 0.8057

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Flow vs P export

y = 13.972x - 1319.9R² = 0.9304

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Figure 4b. The relationship between water flow and NTOT & PTOT export.

The Daugava River

Figure 5. The drainage area (green line) of the Daugava River.

Basic information

The area of the Daugava River’s drainage basin is 86,500 km2. The biggest share of the catchment belongs to Latvia, but large parts are also in Belarus and Russia (Figure 5).

Mean water flow: 791 m3 s-1

Area specific P inputs 18 kg km-2

Area specific N inputs 450 kg km-2

Trends in the export: The Daugava River

In 2014 flow was only 53% of the long term mean flow and nutrient export was also less than 60% of the long term mean: 20,000 t N and 757 t P.

There was a statistically significant increase in P export from 1995 to 2014 (Fig. 6a).

The correlation between flow and export weaker than respective correlation of the Göta and Kemi rivers (Fig. 6b).

Figure 6a. Total N (green bars), total P export (blue bars) and flow (red line) by the Daugava River from 1995 to 2014. The black lines are showing flow-normalised nutrient export and the green dashed lines the trend in the flow-normalised export.

y = 42.869x + 10670R² = 0.4353

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y = 1.5751x + 344.92R² = 0.2962

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Figure 6b. The relationship between water flow and NTOT & PTOT export.

The Nemunas River

Figure 7. The drainage area (green line) of the Nemunas River.

Basic information

The area of the Nemunas River’s drainage basin is 97,900 km2. The biggest part of the catchment belongs to Lithuania and Belarus (Figure 7).

Mean water flow: 624 m3 s-1

Area specific P inputs 18 kg km-2

Area specific N inputs 450 kg km-2

Trends in the export: The Nemunas River

In 2014 flow 22% lower than the long term average flow. The N export was in 2014 32,600 t and P export 1150 t.

Statistically significant decrease in P export could be detected from 1995 to 2014 (Fig. 8a).

The correlation between flow and P export was very weak (Fig. 8b).

Figure 8a. Total N (green bars), total P export (blue bars) and flow (red line) by the Nemunas River from 1995 to 2014. The black lines are showing flow-normalised nutrient export and the green dashed lines the trend in the flow-normalised export.

y = 93.342x - 16426R² = 0.5164

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y = 1.8319x + 869.3R² = 0.0889

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Figure 8b. The relationship between water flow and NTOT & PTOT export.

The Oder River

Figure 9. The drainage area (green line) of the Oder River.

Basic information

The Odra is 841 km long. The Odra river basin is 124.049 km², of which 107.169 km² are in Poland (86.4%), 7.278 km² in the Czech Republic (5.9%), and 9.602 km² within the boundaries of Germany (7.7%) (Figure 9). The source of the river is in the Czech Republic in the Odrzanskie Mountains (Oderské vrchy) at the altitude of 634 m above sea level. 21.4% of the Odra’s water river basin lies 300 above sea level, 54% - between 100-300 m above sea level, 24% - below 100m. The highest point is Śnieżka (Sněžka/ Schneekoppe) in the Giant Mountains (Karkonosze/ Krkonoše/ Riesengebirge) – 1602 m above sea level. For the first 47 km, the Odra has a character of a mountain stream. The drop of the river from Ostrava (Ostrawa/ Ostrau) to the mouth of the Warta is about 27 cm/km, however below Schwedt it is below 5 cm/km. The Odra flows into the Szczecin (Stettin) Lagoon. Large Cities: Ostrava, Opole, Breslau, Frankfurt, Stettin.

Particularly important is the tributary Nysa Łużycka (Lausitzer Neisse) river. The river is 251,8 km long and has a river basin of 4 403,45 km². It is a left tributary of the Odra River, into which it flows on the 542 km of the river’s run. The importance of the river comes from the fact that there are water reservoirs in tree countries: Poland, Germany and Czech Republic as well as from the river’s economic importance and all the international problems it may cause.

The Odra and most of its tributaries are very important ecological passageways of relatively low level of natural environment changes (in relation to the most of the EU rivers). There are seven national parks within the area of the Odra catchment. In the territory of Poland they are: Karkonosze (Karkonoski/Krkonoše/Riesengebirge), Table

Mountains (Góry Stołowe/Stolové hory/ Heuscheuergebirge), Wielkopolska (Wielkopolski Park Narodowy), Drawno (Drawieński Park Narodowy), Ujscie Warty (Park Narodowy Ujście Warty) and Wolin (Woliński Park Narodowy); in the territory of Germany it is the Unteres Odertal (Dolina Dolnej Odry). Moreover, within the Odra river basin there are also landscape parks, nature preserves along with other forms of sanctuaries. Many areas, especially in river valleys, have been protected within a framework of the NATURA 2000.

Mean water flow: 895 m3 s-1

Area specific P inputs 38 kg km-2

Area specific N inputs 874 kg km-2

Trends in the export: The Oder River

In 2014 flow 26% lower than the long term average flow. The N export was 40,000 t and P export 2290 t.

Both N and P export were decreasing from 1995 to 2014 (Fig 10a).

Better correlation between flow and N export than the correlation between flow and P export (Fig. 10b).

Figure 10a. Total N (green bars), total P export (blue bars) and flow (red line) by the Oder River from 1995 to 2014. The black lines are showing flow-normalised nutrient export and the green dashed lines the trend in the flow-normalised export.

y = 124.44x - 3869.3R² = 0.8122

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y = 7.6676x - 455.29R² = 0.5346

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Figure 10b. The relationship between water flow and NTOT & PTOT export.

The Vistula River

Figure 11. The drainage area (green line) of the Vistula River.

Basic information

The Vistula river catchment area covers about 183 176 km2 which is approximately 59 % of total surface area of Poland (Figure 11). 87.5% of the Vistula river basin is located in Poland and the remaining part is on the territory of Belarus, Ukraine and Slovakia. The river basin of the Vistula covers almost the whole eastern part of the country and it is inhabited by 20.8 million people, which is more than half of Poland’s population. The source of the Vistula River is located in southern part of Poland. The mouth of Vistula River is in the Bay of Gdansk.

In Vistula catchment area, the point sources of pollution are mainly related to municipal wastewater treatment plants. The pollutants affecting water bodies are also from industry including the crude oil processing industry, organic and inorganic chemistry plants, paper production, textile industry, iron and steel metallurgy, food industry, shipyards. Another anthropogenic pressure is related to water discharge from mine drainage and leachate from landfills that are not properly protected.

The most important factors responsible for diffuse sources of pollution are agriculture, scattered dwellings and atmospheric deposition. The agricultural land covers about 64.2 % of the river basin and forests are about 30% of total Vistula river basin area. These pressures are reflected in high area specific input figures.

Mean water flow: 1,730 m3 s-1

Area specific P inputs 47 kg km-2

Area specific N inputs 750kg km-2

Trends in the export: The Vistula River

In 2014 flow 13% lower than the long term average flow. In 2014 N export was 64,900 t and P export 7980 t.

N export decreased from 1995 to 2014 (Fig. 12a).

There was a good correlation between flow and export (Fig. 12b).

Figure 12a. Total N (green bars), total P export (blue bars) and flow (red line) by the Vistula River from 1995 to 2014. The black lines are showing flow-normalised nutrient export and the green dashed lines the trend in the flow-normalised export.

y = 101.86x - 11979R² = 0.6333

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Flow vs N export

y = 5.5575x + 334.9R² = 0.7217

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Figure 12b. The relationship between water flow and NTOT & PTOT export.

The Neva River

Figure 13. The drainage area (green line) of the Neva River.

Basic information

The Neva River has the largest drainage basin of all Baltic rivers: 272,000 km2. The biggest part of the catchment belongs to Russia, but also large area is in Finnish territory (Figure 13). The north-eastern parts are in pristine state, whereas the areas along the riverside are densely populated. Europe’s two largest lakes (Ladoga and Onega) are situated in the catchment area and they retain large share of the nutrient inputs from their upstream catchment.

Mean water flow: 2,860 m3 s-1

Area specific P inputs 7.4 kg km-2

Area specific N inputs 187 kg km-2

Trends in the export: The Neva River

In 2014 flow 13% lower than the long term average flow and N export was 49,500 t and P export 2460 t.

A statistically significant decrease in P export could be detected (Fig. 14a).

The correlation between flow and export was weak (Fig. 14b).

Figure 14a. Total N (green bars), total P export (blue bars) and flow (red line) by the Neva River from 1995 to 2014. The black lines are showing flow-normalised nutrient export and the green dashed lines the trend in the flow-normalised export.

y = -14.88x + 90656R² = 0.1464

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Flow vs N export

y = 0.1634x + 2905.2R² = 0.00180

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Figure 14b. The relationship between water flow and NTOT & PTOT export.

Trends in the export: All 7 rivers

In 2014 flow was 7% lower than the long term average flow. The N export was 220,000 t and P export 28,600 t.

Both N and P export was decreasing from 1995 to 2014 (Fig. 15), but the statistical significance has not been tested.

Figure 15. Total N (green bars), total P export (blue bars) and flow (red line) by the 7 big rivers from 1995 to 2014. The black lines are showing flow-normalised nutrient export and the green dashed lines the trend in the flow-normalised export.