The Šešupė river basin is a part of the Nemunas River Basin District (RBD). The territory of the Šešupė sub-basin within Lithuania comprises about 10% of the total area of the largest Nemunas RBD (Figure 1).
The Šešupė sub-basin (Figure 2), covering an area of 6,104.8 km2, was selected as a pilot area for the WATERPRAXIS project in Lithuania. The Lithuanian portion of the Šešupė sub-basin comprises 80% of its total area and 53% of the length of the river bed. The upper reaches of the Šešupė (27 km, catchment area: 287 km2) lie in Poland, while the western part of the middle and lower reaches (62 km, 919 km2) lie in the Kaliningrad region. The river flows 52 km along the border between Lithuania and the Kaliningrad region.
By considering the typology of bodies of water and following the results of a human impact analysis, 70 rivers and 14 lakes were identified in the Šešupė sub-basin.
In eight rivers in the Šešupė sub-basin, water quality parameters are not in compliance with good ecological status requirements. The major identified sources of impacts in the Šešupė sub-basin are: municipal and industrial wastewater and agricultural pollution.
Agriculture accounts for the largest share of diffuse pollution. In the Šešupė sub-basin, as much as 75-80% of nitrate nitrogen enters water bodies as a result of agricultural pressures. According to the data on the area deemed agricultural land, arable land in the Šešupė sub-basin constitutes as much as half of the total area of sub-basin. A high density of animals (in respect of the total area of the sub-basin) has also been observed in the Šešupė sub-basin.
The annual water consumption in the Šešupė sub-basin is about 10,400 m3. The water consumption level in the Šešupė sub-basin is low (about 5% of household consumption in the Nemunas RBD) compared to other sub-basins in the Nemunas RBD.
In a number of groundwater wellfields in the Šešupė sub-basin, the concentrations of two indicators, sulphates (SO4) and chlorides (Cl), fail to conform to the requirements for drinking water quality. About 87% of the groundwater bodies investigated and around 55% of the groundwater wells used for potable water do not meet the requirements for iron concentration in water (≥0.2 mg/L).
Economically feasible solutions are needed for good-quality drinking water in small settlements. EU and national financial mechanisms do not cover drinking water quality improvement measures in small settlements.