The territory of Poland lies in the catchment areas of the Baltic, Black and North Seas, to which waters, 99.7%, 0.2% and 0.1% respectively, from the territory of the country are drained.

Surface waters in Poland occupy 8,313 km², which is 2.7% of the territory of the country. Lakes and rivers with dammed reservoirs dominate among these surface waters.

Wetlands, marshes and peat-bogs play an important role in shaping the water resources of Poland. The Bagna Biebrzanskie, occupy an area of 1,400 km² and are the largest of the wetlands. This area was recognised as a natural retention reservoir and was officially rendered a National Park in 1993. Unfortunately, due to improper water drainage and a drought which has lasted for the past several years, the surface area of the wetlands, marshes and peat-bogs is deteriorating constantly and permanently.

The water resources on the territory of Poland result from the yearly water input and output. 97% of the water input is shaped by atmospheric precipitation. Evaporation and transpiration constitute main outputs, accounting for nearly 70% of water loss. River run-off, on the other hand, describes the size of water resources, and is characterised as changing from season to season and from year to year. In the years 1950–1995, surface water resources measured on average 61.0 km³, approximately 1,550 m³ per person. This figure is three times lower than the European average and five times lower than the world average.

The small water resources are distributed throughout Poland unevenly. The belt of the Srodkowopolskie Lowlands suffers from surface water deficit, which is mainly a result of the precipitation deficit. The size of the areas which suffer from surface water deficit is estimated to be 38.5% of the territory of Poland.

The amount of river run-off in Poland fluctuates from year to year, from about 30–90 km³. Due to varying seasonal precipitation, much of the river run-off has a seasonal character. Because of its seasonal character, only 95% of river run-off data is used as a basis for available resource calculations. The available resources are estimated to measure 22 km³. After subtracting the amount of inviolable resources from the estimated 22 km³, the remaining amount of water reservoirs which ensure the functioning of the water ecosystems, is 15 km³. Each year, 7 km³ of water resources are used for economic purposes.

The successful undertaking of enlarging water reservoirs depends on the development of natural (soil) retention and artificial (dammed reservoirs) retention.

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