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Salaca River Einzugsgebiet

SALACA RIVER BASIN SHORT CHARACTERIZATION


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The Salaca River starts its 95 km long flow as a dozen meters wide stream from the Lake Burtnieks – the fourth biggest lake in Latvia to Riga Bay. The Salaca River Basin is the fifth largest in Latvia - 3191,2 sq. km and it forms the heart of North – Vidzeme Biosphere Reserve (NVBR). 98% of the Salaca River Basin is located in Latvia (3191,2 sq. km in Latvia and 228,8 sq. km in Estonia) and it comprises four sub – basins, namely:

 

·  Salaca River downstream Ige (sub-) basin (between Staicele and Mazsalaca towns);

·  Ige River (sub-) basin (Aloja town);

·  Salaca River between Ige and Lake Burtnieks (sub-) basin (Mazsalaca town;

·  Lake Burtnieks (sub-) basin (Rūjiena and Valka towns).

 

The Salaca River basin comprises a total of 3,570 sq km and has rather complex surface characteristics. The Lake Burtnieku basin accounts for 2,290 sq km, or approximately 60% of the Salaca River Basin.

The lake is 13.3 km long and 5.5 km at its widest point, covering a total of 40.1 sq km with a shore length of 33 km.

Average depth is 2.2 m and maximum is 3.3 m with a sandy bottom and long sand bars.  There are two islands – Enksāre and Cepurīte. The south shore of the lake is steep, in places up to 20m, occasionally revealing sandstone. The Salaca River flows out of the northwest end of Lake Burtnieku.

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In its upper and middle reaches the Salaca River flows through a terraced valley in the Burtnieku and Metsapoles plain.  In its lower reaches it flows through the Vidzeme coastal area emptying into the Gulf of Riga at the city of Salacgrīva. Forests cover approximately 30% of the river’s basin and 12% are swamplands. There are 160 lakes within the basin and 11 rivers each longer than 20 km. Compared with other rivers the Salaca is relatively winding and contains many sand bars and rapids. The river is generally 25 to 55 meters wide increasing to 100 to 150 meters and up to 200 meters at its mouth. Water depth is 0.7 – 2.7 m with occasional 8 m deep spots. The river valley is about 20 m deep, narrow and with steep sides, occasionally revealing red devon sandstone.

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The Salaca River Basin, including Burtnieks, is within the climate zone of north Vidzeme. Its variable and contrasting climate is due to the segmented surface contour. To the south from Staicele the Idumeja hill area influences the local climatic conditions which result in more than 800mm of precipitation annually in the river’s lower reaches. The rest of the area receives 700 to 800 mm, and in warmer seasons only about 500 mm.

About 60 to 65% of the total precipitation flows as surface and subsurface waters. These are favorable conditions in the formation of river networks and wetlands. The growth period for vegetation averages 180 – 190 days.  Air temperatures range from – 6o in January to + 17o in July. Arriving air masses from the sea are subject to significantly changing conditions in short time periods, accompanied by increases in precipitation. Besides affecting precipitation, the basin’s proximity to the sea and its relatively flat ground surface, about 40 to 80 m above sea level, contribute to gusty wind conditions inland.  The only windbreaks are forests.

The Salaca River is rich in biodiversity. Taxonomy reveals more than 330 macrozoobenthos organisms. Theses are the result of favorable conditions created by rock formations, rapids and varying water flow rates, and oxygen concentrations together with biological quality and lighting which contribute to the development of biotypes such as Potamogeton alpinus, Fontinalis sp., and Hildenbrandia rivularis. The morphology of virtually all biotypes here corresponds precisely to their definitions, and at present there are no negative influences, or their effect is not significant.

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The waterfauna also is determined by the varying environment and the influences of Lake Burtnieki and the Bay of Riga. A total of 42 species of fish, including lampreys, have been identified. Most (30) are freshwater species, some of which at various times are found in the coastal waters of the Bay of Riga.

 

Copyright © Günter Feuerstein