The Sulejów Reservoir (Figure 1) was constructed in the years 1969-1973 by impounding the Pilica River with a dam at the village of Smardzewice. It is a typical lowland, low-volume artificial lake with large areas emerging when low water levels occur.The Sulejów Reservoir is defined by the following parameters:
- length – 17,1 km
- maximum width – 2,1 km
- average width – 1,5 km
- average depth – 3,3 m
- maximum depth – 11 m
- shoreline length - 58 km
- surface area - about 22 km2
- usable capacity - 61 mln m3
- maximum capacity – 75 mln m3
- drainage basin area – 4 900 km2
The reservoir is located on the territories of four communities: Wolbórz, Sulejów, Tomaszów Mazowiecki and Mniszków. The whole drainage basin of the reservoir is a farm (64%) and forest (30%) area. For nearly 30 years, the main function of the reservoir was to supply the cities of Łódź and Tomaszów Mazowiecki with drinking water; however, problems with water quality (algal blooms) restrict this function nowadays. The main functions of the Sulejów Reservoir today are: retention, recreation, energy production (2,5 – 3 MW) (Figure 2) and fire protection.A sanitary system has not been developed completely around the reservoir, which facilitates sewage discharge and direct surface flows into the water body. The reservoir waters are marked by high oxygenation along with supersaturation during the bloom period. Alkalization takes place during the strong growth of phytoplankton. As a result, the nutrients are desorbed from the bottom deposits, which periodically contribute to the mass growth of algae, particularly their blue-green genus. This causes a disturbance in the ecological balance of the ecosystem. The algae may have carcinogenic and toxic effects on humans, by degrading the liver cells, damaging the nervous system or irritating the respiratory muscles.
The analysis of water quality, threats and conflicts occurring in the area of the Sulejów Reservoir, allows to construct a matrix of interactions and anthropogenic pressure influencing the water quality. The matrix shown in Figure 3 illustrates the relations between the environmental conditions of water in the Sulejów Reservoir and factors causing deterioration of its quality.
The key ecological issues in the Sulejow reservoir region are as follow:
- Non-point sources pollution of the Pilica and Luciąża Rivers, resulting from agricultural use of the catchment; high nutrient loads transported by the rivers.
- Point-sources pollution severely impacting the water quality of the river:
- unstable sewage treatment technologies at the sewage treatment plants
- exceeded chemical and biological standards in the sewage released to the river from the treatment plants,
- eutrophication and periodically increased bacteriology in the river
- Toxic algal blooms in the Sulejów Reservoir
- blue-green algae blooms restricting the use of the reservoir as a drinking water supply and recreational area.