The Stryama is a river in southern Bulgaria, an important left tributary of the Maritsa. It originates in the Balkan Mountains. The river is 110 kilometres in length and is the sixth longest in the Maritsa drainage, following the Tundzha (390 km), the Arda (290 km), the Ergene (281 km), the Topolnitsa (155 km) and the Sazliyka (145 km).

The Topolnitsa is a river in southern Bulgaria, an important left tributary of the Maritsa. The river's name is derived from the Bulgarian word топола, topola ("poplar"). Reaching length of 155 km, the Topolnitsa is the fourth longest river in the Maritsa drainage, following the Tundzha (390 km), the Arda (290 km) and the Ergene (281 km).