Freshwater - State and impacts (Latvia)

Water quantity:

Latvia is one of the richest states in the world in terms of fresh water resources, given the size of the country’s population.

Freshwater resources far exceed present and future requirements for water consumption. In Latvia, the Water Exploitation Index (WEI) is one of the lowest in the European Union. Moreover, it has decreased from 0.013 in 1990 to 0.007 in 2005, due to economic and institutional changes and water saving and water efficiency measures.

• CSI 018 Use of freshwater resources

Water quality:

• The eutrophication of inland surface water and marine water - particularly in the southern part of the Gulf of Riga - is a major environmental     problem
• In general, the nitrogen concentration in rivers is increasing slightly
• There is no common trend for the annual average phosphorus concentration in rivers; it varies between rivers and depends on the different socioeconomic, climatic and hydrological conditions in each river basin district
• The concentration of oxygen-consuming substances in rivers is low and this generally indicates good water quality.

Ecological quality of water bodies

Figure 1: Ecological quality of inland surface water bodies in Latvia

Source: Latvian Environment, Geology and Meteorology Centre

River Basin Environmental Reports (in Latvian) River Basin Management Plans (in Latvian)

The territory of Latvia is sub-divided into the catchment areas of four large rivers to create the Daugava, Gauja, Venta and Lielupe river basin districts.

According to the information included in the first river basin management plans, 51 % of surface water bodies are currently considered to be of high or good ecological quality (Table 1). The main cause of inadequate surface water quality is eutrophication due to pollution from point and diffuse sources, morphological changes in rivers and an influx of biogens from neighbouring countries via transboundary watercourses.

Table 1: Ecological quality of inland surface water bodies in Latvia

Source: Latvian Environment, Geology and Meteorology Centre

Nutrients in the largest rivers

Figure 2: Annual average concentrations of nitrogen in river estuaries

Source: Latvian Environment, Geology and Meteorology Centre

Since the beginning of the 1990s the annual average concentration of nitrogen in rivers has decreased and does not exceed 2 mg/l in Daugava, Gauja and Venta. In Lielupe, the concentration of nitrogen is higher due to intensive agriculture activity in this region. In 2007, the average nitrogen concentration in Lielupe exceeded 6 mg/l. However, despite a variability in the overall average nitrogen concentration from year to year, the recent trend indicates a small increase in nitrogen concentrations in all rivers.

In Lielupe, the annual average concentration of total phosphorus has changed significantly compared with other rivers. This is partly explained by climatic and specific hydrological conditions in the catchment area.

Figure 3: Annual average concentrations of phosphorus at river estuaries

Source: Latvian Environment, Geology and Meteorology Centre

Point and diffuse pollution sources have the most significant impact on the ecological quality of inland water. Transboundary pollution also affects freshwater quality. More than 50 % of the total run-off from rivers in Latvia originates in other countries and contains significant amounts of pollutants, particularly nutrients. The largest rivers receiving pollution from neighbouring countries are the Daugava, Lielupe and Venta.

It is estimated that more than 70 % of the total nitrogen and more than 40 % of the total phosphorus inland load is caused by various human activities – e.g. waste water discharge or run-off from agricultural land and forests. The agricultural sector generates the largest proportion of nitrogen discharge and the main source of phosphorus is municipal and industrial waste water.

CSI 020 Nutrients in freshwater

Oxygen-consuming substances in the largest rivers

Figure 4: Pollution by oxygen-consuming substances at river estuaries

Source: Latvian Environment, Geology and Meteorology Centre
 

In recent years, the annual average concentrations of BOD₅ have decreased in Venta and Daugava, but this trend has not been observed in Lielupe and Gauja. BOD₅ values observed during the period 2001–2008 are generally less than 2 mg O₂/l and are typical of good quality water. Values between 2 and 2.5 mg O₂/l indicate only slightly polluted surface waters.

CSI 019 Oxygen-consuming substances in rivers