The Trnava Dam is one of three dams built in the surroundings of the small town Želiv. It was built on the Trnava river about 1 km south of Želiv.

The construction of this hydroengineering structure finished in 1981. The dam is used for catching sewage waters from the basin of the Trnava river. It protects water in the Švihov Dam (down the stream), which is used as a source of drinkable water for Prague.

The revetment is 15 m high and 205 m long (at the crest). Its area is 85 ha and it is 6 km long. The dam contains about 6.5 million cubic metres of water and its maximal depth is 12 m.

The access to the dam is possible along the road from Želiv. The red marked path leads from Želiv along the dam. The path goes over the lake and continues to the small town Červená Řečice. The yellow marked trail goes along the dam in its southern part.