Slapy is located in the Central Bohemian Region, in the Benešov Uplands.

Slapy has an area of the water surface of 11.63 km2 (4.49 sq mi) and total capacity of 269,300,000 m3 (218,300 acre⋅ft).

The current water level is 35 metres higher than the original bed of the Vltava.

The construction of a lock was planned, but due to time and financial reasons, it was not implemented.

The reservoir also partially protects the area under the dam (especially the city of Prague) from floods.