The
Topolnitsa is a river in southern
Bulgaria, an important left tributary of the
Maritsa. It takes its source from Bich Peak in
Sredna Gora close to
Koprivshtitsa; it is known as the Shirineyska in its upper course. Its average
discharge is 55 m³/s and it is long; its
drainage basin covers . The Topolnitsa flows into the Maritsa near
Pazardzhik after making a large turn under
Trakiya motorway. The
Topolnitsa Reservoir has a maximum volume of and serves the area around Pazardzhik. Among the Topolnitsa's tributaries are the Mativir and the Bunovo River. The river's name is derived from the Bulgarian word топола,
topola ("
poplar").