Freshwater - State and impacts (Lithuania)

Lithuania has four official river basin districts that are part of the Baltic Sea region. The average annual river discharge is around 25 km³. According to the water status classification criteria derived in accordance to the requirements of the Water Framework Directive (Directive 2000/60/EC), some 47 % of the water bodies in Lithuania’s largest river basin, the Nemunas Basin, fall within the group at risk. Lithuania has over 80 operating hydropower plants, built by damming some 50 rivers and this has made approximately 80 % of the country’s territory inaccessible to migrating fish (Fig. 1).

According to national monitoring data, the quantity of substances entering rivers and enhancing eutrophication, such as  nitrogen and  phosphorus, has declined while the percentage of clean rivers has been increasing on an annual basis (Fig. 2).

On average, groundwater meets quality standards at 90 % of the monitoring sites. The highest levels of nitrates are observed in urban areas or zones of intensive agriculture. Lithuania began monitoring the status of groundwater resources in 1946. Data on the groundwater level indicate that changes in climatic conditions have had a negative impact on groundwater resources in recent years. Dry springs followed by hot, dry summers have an adverse effect on groundwater resources. The groundwater level is an indicator of a dry period in the subsurface (Fig. 3).

The most sensitive areas are lowland zones, made up of glacial and lacustrine deposits with low permeability (clay, till), where the loss of groundwater resources is higher than groundwater recharge.

In 2007, groundwater levels indicated the end of a dry period. However, the weather conditions in 2008 were unfavourable for groundwater resources. In glaciolacustrine lowlands, where shallow groundwater occurs at a depth of less than 3 m, the rate of evaporation is higher than that of recharge. Consequently the balance of groundwater resources was negative in 2008 (-2.96 m³/s). In glacial lowlands, where shallow groundwater is found in glacial deposits and glaciolacustrine sandy lowlands at a depth of below 5 m, annual groundwater resources were 1.51 m³/s. The best situation was observed in sandy glaciofluvial lowlands and highlands where natural groundwater resources were close to the long-term average. However, natural shallow groundwater resources throughout the country were below the long-term average (Table 1).

Table 1. Groundwater resources