The river Spengla flows in Trakai and Varena districts, the river Merkys right tributary. Length of the river 30 km, the basin area 123 km ². The source in Gudarastis swamp at Gudakiemis village, 8 km east from Onuskis town. Flows to southeast through the lakes Galvoezeris and Spengla. The Spengla flows into the river Merkys 83 km from its mouth, 4 km southwest from Valkininkai village. Average gradient 102 cm/km. Average rated discharge at the mouth 0.96 m³/s.

Not recommended in dry summer.
Rapids, shalows, low footbridges, strainers.
WW 0/1- (1+).

18.4 Bridge. right Mazieji Lieponiai. Average gradient to the right brook 111 cm/km. The channeled river flows through meadows, width 5 m. In some places small shallow rapids.
16.3 Small bridge. right Kalviai.
15.8 Small bridge. right Kalviai.
15.5 Bridge. right Kalviai.
15.1 Small bridge. left Kalviai.
13.8 right the brook S-2.
12.1 right Lielukas.
10.7 Rudiskes - Varena road bridge.
10.5 Railway bridge. Under the bridge small rapid. Downstream left Vaitakarcmis. To Puckorne village a few low footbridges. Can be beavers dams. The river channeled.
9.9 Bridge. left Vaitakarcmis.
8.7 Small bridge. left Puckornes. Channeled section of the river ends.
8.3 Bridge. Puckornes. Near the river forests. The banks overgrown by rare trees and bushes.
7.3 Small bridge.
6.4 Steel bridge. right Valkininkai. Can be fallen to the riverbed trees.
5.0 Vilnius - Alytus highway bridge. Under the bridge small rapid. The current accelerated, depth decreases, sandy bottom replace gravel. To the mouth rare small shallow rapids. The river flows through forest. The banks in some places high, a few outcrops up to 10 m height. Strainers not a lot.
2.3 The remains of former Spengla water mill.
1.6 right the brook from small lake. Strainers in the river bed. Average gradient to the mouth 244 cm/km.
0.0 The Spengla flows into the river Merkys.