LATVIJAS VIDES, ĢEOLOĢIJAS UN METEOROLOĢIJAS AĢENTŪRA © LVĢMA AQUATIC ECOSYSTEMS OF LATVIA T....

LATVIJAS VIDES, ĢEOLOĢIJAS UNMETEOROLOĢIJAS AĢENTŪRA

© LVĢMA

AQUATIC ECOSYSTEMS OF LATVIAT. Kolcova and I. Mikelsone

GENERAL INFORMATION

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© LVĢMA T. Koļcova, I. Miķelsone

•Forests cover a total of 44% of the country, 10% consists of peat bogs, 2-3% is fresh water reservoirs, 38% is used for agriculture and 4% is taken up by towns, villages and roads.

•Latvia is situated in the North-eastern Europe on the coast of the Baltic Sea. It borders with Estonia in the north, Lithuania in the south, the Russian Federation in the east and Belarus in the southeast direction. The seacoast length is 494 km. The total land border is 1862 km.

•The coastal plain is mostly flat, but inland to the east the land is hilly with forests and lakes.

• All rivers of Latvia discharge into the Baltic Sea or to the Gulf of Riga (part of the Baltic Sea). More than 12,000 streams are located in Latvia. Percentage of small rivers of a length of less than 10 km is 95%; only 17 are longer than 100 km. The drainage basins of large streams cover about 80% of the Latvian territory. Only the one river (Daugava River) has a length of more than 500 km.

• The lakes cover 1.3% of the Latvian territory. The total area of the lakes is about 1,000 km²; the number of the lakes amounts to 3,000. Most of them have an area of the water plane of less than 0.5 km². Latvian lakes are shallow with mean depth of 1-5 m, only 8 of them are deeper than 10 m.

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GENERAL INFORMATION


River basin

district

Number of river water

bodies

Total length of rivers

(km)

Surface area of RBD (km2)

RBD area comparing with total area of

Latvia (%)

Daugava 66 8322,927 27062,1 41,89

Lielupe 33 3144,431 8849,27 13,70

Venta 63 4972,762 15625,24 24,22

Gauja 45 4234,954 13050,94 20,20

Total: 207 20675,074 64587,55 100,00


AQUATIC ECOSYSTEMS

• Any watery environment, from small to large, from pond to ocean, in which plants and animals interact with the chemical and physical features of the environment.

• Aquatic ecosystems of Latvia: freshwater ecosystems; estuarine ecosystems; coastal water ecosystems.



FRESHWATER ECOSYSTEMS

The main freshwater ecosystems of Latvia:

- Daugava River basin;- Gauja River basin;- Lielupe River basin;- Venta River basin -




FRESHWATER ECOSYSTEMS: DAUGAVA RIVER BASIN

GEOGRAPGY:•The drainage basin of Daugava River stretches from the Valday Massive in the central part of European Russia to the Gulf of Riga and crosses the northeast of Belarus.

•The length of the basin is 700 km, the maximum width – 225 km.

•Total area covered by the Daugava basin exceeds 87 900 km², within Latvia – 24 700 km².

•The mean slope of Daugava River is 0,54 ‰. - Lakes cover around 3% of the Daugava basin area, mire – 7%. - - Biotops: forests (39%), pastures (14%), meadows (7%), wetlands (3%).


FRESHWATER ECOSYSTEMS: DAUGAVA RIVER BASIN


CLIMATE:

The influence of Polar Maritime air masses of the North Atlantic origin gradually increases moving from the upstream to the downstream parts of the basin.

- monthly avg. air temperature;

- annual precipitation;

- annual evapotranspiration – 450 mm;

- snow cover duration 70-80 days,

- ice cover formed in the upstream part at the beginning

of December but in the downstream – at the

end of December.

-4,3°C (Jan.)

-6,9 °C (Jan.)

16,9 °C (Jul.)

17,6 °C (Jul.)

800 mm635 mm


FRESHWATER ECOSYSTEMSDAUGAVA RIVER BASIN


HYDROLOGY:•The average density of river network is 830 m/km.

•There are 8 rivers longer than 100 km, and 6 lakes lager than 10 km²

•Hidrological regime: high spring flood, summer-autumn rainfall floods, summer and winter low flow periods, winter floods caused ice jump.

•Feeding: snow melt (50%), ground water (30-35%) and rainfall (15-20%).

•Mean annual Daugava River water runoff is 710 m³/s.

230 mm

280 mm

380 mm


FRESHWATER ECOSYSTEMSLIELUPE RIVER BASIN


•The river basin area is 17 633 km², within Latvia – 8 750 km². The average slope of Lielupe River is 0,48 ‰. The river bed is much lower than average Baltic Sea level over a length of 100 km upstream from the mouth. -Lakes cover less than 1% of the Lielupe basin area, forest – 30% and mire cover 10%. -Karst area along the border.

- the Memele River (Nemunelis in Lithuania) approx. 191 km in length of which 78 km in Lithuania, 29 km in Latvia and 84 km along the border, originates from the Aukstaitia heights.

•The river has two major branches; - the Musa River 164 km in length of which 140 km in Lithuania, 18km in Latvia and 6 km along the border, starts from the Tyrelis bog in Lithuania (87 m a.sl.)




CLIMATE:

The influence of Polar Maritime air masses of the North Atlantic origin.

- monthly avg. air temperature; -5,0°C (Jan.) and 17,0-18,0 °C (Jul.)

- annual precipitation: 500-550 mm

- snow cover duration: left bank - 88 days, right bank – 99 days;

- ice cover formed at the middle of December.

550 mm

500 mm





•There are 8 rivers longer than 100 km, and 1 lake lager than 10 km²

•Hydrological regime: high spring flood, summer-autumn rainfall floods, summer drought and winter low flow period interrupted by thaws.

•Feeding: snow melt (50%), ground water (5%) and rainfall (45%).

•Mean annual water runoff is 110 m³/s.

150 mm

220 mm



FRESHWATER ECOSYSTEMSGAUJA RIVER BASIN

•The river basin area is 8900 km², within Latvia – 7790 km², the river length is 460 km.

•The average slope of Gauja River is 0,50 ‰.

•Lakes and mire cover 1% of the Gauja River basin area, forest – 40%.

•The Gauja River basin starts from the small mire in Cesis administrative region on the high of 240 m a.s.l. The river basin middle and upper parts locate on the Vidzeme upland, and only lower riches cross the Gulf of Riga lowland.




CLIMATE:


- monthly avg. air temperature: in the southeast part of basin -6,7 °C (Jan.) and 16,6 °C (Jul.), and in the lower part: -4,3 °C (Jan.) and 17,6 °C (Jul.);

700 mm870 mm


- snow cover duration: 85-110 days;

- ice cover formed at the beginning of December in the river upstream and at the middle of December in the downstream.




HYDROLOGY:

•Feeding: snow melt (35%), ground water (35-40%) and rainfall (25-30%).

•Mean annual water runoff is 75,0 m³/s.

•The average density of river network is 390 m/km.

•There are 7 rivers longer than 100 km.

•Hydrological regime: high spring flood, summer-autumn rainfall floods, summer and winter drought.

360 mm

240 mm



FRESHWATER ECOSYSTEMSVENTA RIVER BASIN

GEOGRAPGY:

•The drainage basin of Venta River stretches from the lake Zvirgzas in Lithuania to the Baltic Sea nearby Ventspils city.

•The length of the river is 346 km, within Latvia – 176 km.

•Total area covered by the Venta River basin exceeds 11830 km², within Latvia – 7900 km².

•The mean slope of Venta River is 0,5 ‰.

•Lakes cover less than 1% of the Venta basin area, mire – 5%, forests – 20%.




CLIMATE:


- monthly avg. air temperature river downstream area is -2,7 °C (Feb.) and 16,7 °C (Jul.) bet upstream area –4,3 °C (Feb.) and 16,6 °C (Jul.);


- snow cover duration: 65-75 days;

- on lower part of basin ice cover formed at the beginning of January bet in 30% of the observation period rivers don’t freeze.

-2,7°C (Feb.)

16,7 °C (Jul.)

-4,3°C (Feb.)16,6 °C (Jul.)





•There are 3 rivers longer than 100 km and 1 lake lager than 10 km.

•Hydrological regime: high spring flood, autumn and winter rainfall floods and summer drought.

•Feeding: snow melt (55%), ground water (<10%) and rainfall (35%).

•In lower part of river basin mean annual water runoff is about 280 mm, in upper part 240-260 mm on the right bank and 280-300 mm on the left bank of Venta River basin.

240 mm

300 mm




GEOLOGY:

All the rivers of Latvia, including the Daugava, Venta, Lielupe and Gauja River basins, can be divided into 3 types according to geological conditions:

-rivers with carbonated riverbeds mainly composed of Devonian sediments: dolomite, clay, dolomite marlstone, and limestone ;

-rivers with sandy riverbeds mainly composed of quaternary sediments: sand, sandstone, clay, sand-gravel, loam;

- rivers with organic originated riverbeds composed of postglacial sediments: mainly peat.



FRESHWATER ECOSYSTEMSGROUNDWATER

•The thickness of active water exchange zone range between 10 m in the Northern part of Venta River basin and 400 m in the Southern part of Venta River basin and the Eastern part of Daugava River basin .

•The main infiltration areas are located in the areas of higher altitude, namely in the Highlands of Rietumkursa, Austrumkursa, Ziemeļkursa, Idumeja, Vidzeme, Alūksne and Latgale. From there groundwater flows to the direction of the Baltic Sea, Riga Gulf and valleys of big rivers.


© LVĢMA T. Koļcova, I. Mikelsone

FRESHWATER ECOSYSTEMSGROUNDWATER

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© LVĢMA T. Koļcova, I. Mikelsone


•The total catchments of fish and lamprey in Latvian priority waters exceed 80 % of the total catchments in Latvian inland waters.

•23 fish species are reported in lake catchments statistics;

•only 8 of them may be regarded as economically significant: bream, pike, roach, pikeperch, tench, perch, Crucian carp and eel.

•Our rivers are used as spawning grounds by 5 economically significant species - salmon, sea trout, European smelt, vimba and river lamprey. It is estimated that there are about 100 000 anglers in Latvia

There is a large number of species of aquatic flora and fish fauna in the Latvian aquatic ecosystems.


© LVĢMA T. Koļcova

COSTAL WATER ECOSYSTEMS

•Seaward border of the Latvian coastal waters typically goes along the Latvian coast between isobaths of 10 and 15 m. The only exception is the coastal stretch between Kolka and Roja in the Riga Gulf, where a maximal depth of coastal waters reaches 25 m.

•The average depth of Latvian coastal waters is about 7 m, with the exception of Kolka – Roja stretch, where an average depth is 13 m.

•Bottom substrate of the Latvian coast consists of sand and gravel of different granulometric size, which is interrupted by more or less extensive aggregations of boulders and smaller stones and, at some places, by underwater exposures of limestone.



COSTAL WATER ECOSYSTEMS

F i g u r e 1 . 1 . 9 . 4 . 1 . C o a s t a l a n d t r a n s i t i o n a l w a t e r b o d i e s i n t h e

R i g a G u l f

F i g u r e 1 . 1 . 9 . 4 . 2 . C o a s t a l w a t e r b o d i e s i n t h e B a l t i c S e a

F i g u r e 1 . 1 . 9 . 4 . 3 . C o a s t a l w a t e r b o d i e s i n t h e B a l t i c S e a


© LVĢMA T. Koļcova, I.Mikelsone

ESTUARINE ECOSYSTEMS

•The main Latvian estuarine ecosystem is located in the southern part of the Riga Gulf, in the vicinity of Daugava, Lielupe and Gauja river mouths. The 10% deviation from annual mean salinity is used as a criterion for establishing of boundary of transitional waters in the large river plume extending offshore.

•The average salinity of the Gulf of Riga surface layer is 5,26 practical salinity units; therefore the boundary of transitional waters is defined by 4,7 practical salinity units isohaline.



•Area includes specific ecosystem shaped by the presence of the mixing zone. Presence of both freshwater and brackish water plankton and benthos species is characteristic there, as well as excess nutrients, dissolved and particulate organic matter, that originate in Daugava and Lielupe river basins.

The average depth of the transitional water basin is 22 m, thus according to the mixing conditions it may be classified as “partially stratified”.

The estuaries of Lielupe and Gauja Rivers usually freeze up at the middle of December, and ice cover period lasts 95 days an average. On Daugava River ice cover formation starts in the beginning of January bet is destroyed artificially.




TypeSalinity(PSU)

Depth(m)

Wave exposure Mixing

Residence time (days)

SubstratumIce cover

(days)

South-eastern exposed Sandy coast

6 < 18-20 <30 Exposed Permanently full

<7sand-gravel

Irregular

South-eastern exposed Stony coast

6 < 18-20 <30 Exposed Permanently full

<7 cobble Irregular

Gulf of Riga Sandy Coast

0,5 < 6 <30moderately

exposedPermanently

full<7

sand-gravel

Irregular

Gulf of Riga Stony Coast

0,5 < 6 <30 moderately exposed

Permanently full

<7 cobble Irregular

COSTAL AND ESTUARINE WATER ECOSYSTEMS



•Latvia marine monitoring program includes both sediments and biota: fish and molluscs. Contents of toxic substances in perch (Perca fluviatilis) and molluscs (Macoma balthica) are studied in the Riga Gulf.

•Contents of lead, cadmium, copper and zinc are determined in fish liver; contents of mercury in muscle, and all the abovementioned metals are determined in tissue of molluscs.


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