Water

 POLLUTION OF SURFACE WATER

 

Pollution of surface water in Riga is of particular worry as it entails pollution of the Baltic Sea . Besides, as surface water infiltrates into the ground, contamination of ground water occurs. Surface water is a significant recreational resource. Large lakes and rivers play an important role for the fisheries domain.

Pollution of surface water reduces the recreational value of such water, endangers replenishment of the fish stock and bears a direct impact on the quality of water in the Baltic Sea .

 

On the national level water quality of Riga`s small rivers is assessed by Greater Riga Regional Environmental Board, Daugava River and Kisezers (lake) - by Latvian Hydrometeorological Agency (Since 2002 by Latvian Environmental Agency). On the municipal level in 1995 Environmental Department of Riga City Council created monitoring network (16 monitoring sites) of the City to assess the inland water quality. This monitoring was into operation from 1996 to 1998 and unfortunately was stopped later.

 

 

 

 WATER QUALITY IN THE DAUGAVA RIVER

The water in the Daugava River can be considered as moderately polluted in the territory of Riga. The quality of water in the river is very much impacted by the pollution created in the Daugava River drainage basin.

Daugava River within Riga City territory is designated as Cyprinid waters that are waters, which support or become capable of supporting fish belonging to the cyprinids (Cyprinidae ) as well as species such as pike (Esox lucius), perch (Perca fluviatilis) and eel (Anguilla anguilla ). for these waters national target values harmonized with Freshwater Fish Directive 78/659/EEC are set by RegulationNo 118 of the Republic of Latvia Cabinet of Ministers. The concentrations of quality parameters for Cyprinid waters (Regulation No 118 of the Republic of Latvia Cabinet of Ministers) are within ranges of target values except NH 4/N concentration in 1997 (see Figure 36) . The concentrations of oxygen vary from 8 to 11 mg/l (target value 5 mg/l). Thus it should be concluded that despite of the impact of urban environment, r iver is still suitable to the fish of carp family. According to the data of the National Hydrometeorological Administration, the least concentration of oxygen has been observed at Milgravis where it is no higher than 5,99 mg/l or with a saturation of 66 % (less than the standard used in evaluating surface waters suitable to fish of the carp family).

In the water of the Daugava, the content of organic substances also exceeds the required water quality standards.

There are three state monitoring points on Daugava River - downstream Doles Island, at Milgravis,  in estuary.

In period from 1995 to 1999 the mean annual concentrations of total nitrogen fluctuates between from 0.72 to 1.96 mg/l, total phosphorus - from 0.007 to 0.076 mg/l, saprobic index by macrozoobenthos - from 1.99 to 2.93 (see Figure 35). According this data water quality of Daugava River varies from slightly polluted to polluted by biological assessment system based on examination of macroinvertebrates (The Standard of Latvia Republic LVS 240:1999)

The water is much impacted by the Riga Port terminals and industrial sites close to the estuary. In Milgravis, water contamination with petroleum products is 4 times higher than the maximum permissible concentration and increasing over the last years (see Figure 29).