The Sulejów Reservoir is a typical, shallow lowland reservoir, taking up a large area.

- The Reservoir was created in 1969–1973 as a result of damming the Pilica river near the village called Smardzewice. A concrete and soil dam with the length of 1200 m and the height of 16 m was constructed on the 139th kilometer from the mouth and resulted in the creation of a reservoir with the surface area of 2700 ha.

- The reservoir water supply comes mainly from two rivers: Pilica and Luciąża.

- Basic description of the Sulejów Reservoir:

• 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 approx. 27 km²,
• usable volume 61 mn m³
• maximum volume 75 mn m³
• catchment area 4,900 km².

The Sulejów Reservoir is particularly susceptible to eutrophication, caused mostly by long water retention (40 days), low average depth, inflow of waster from the direct catchment area and the supply rivers: Pilica and Luciąża. The eutrophic character of the waters is caused by excessive load of biogenic substances, especially phosphorus, fed into the reservoir from both local and area sources. The most disadvantageous manifestation of the increased water fertility are toxic cyanobacterial blooms in the vegetation period. The presence of algae disqualifies the reservoir as a source of potable water but also limits its recreational functionalities. Contact with cyanobacteria in water may cause allergic reaction, both dermatological and gastric. Consumption of even small amounts of cyanobacteria toxins in water for prolonged periods of time may result in liver or colon cancer.
The quality of water in the reservoir depends mostly on the level of the supply rivers. 64% of the areas around the reservoir are used for farming purposes, there are no factories or large industrial plants in close proximity causing direct pollution. All in all, for many years the reason for the unsatisfactory condition of the environment have been surface run-off from agricultural areas, sewage from leaking septic tanks and areas without a central sewage system, resulting in the loss of biodiversity and the reduction of the environmental value of the local ecosystem.