The river Zvelsa flows in Plunge and Telsiai districts, the river Minija left tributary. Length of the river 38 km, the basin area 144 km ². The source in Dausynos forest, 5 km north from Endriejavas town. Flows to west. Flows into the river Venta 62 km from its mouth at Zvelsenai village, 5 km north from Gargzdai town. Average gradient 268 cm/km. Average rated discharge at the mouth 1.87 m³/s.

At higher water level. Spring, or after heavy rains.
Rapids, shalows, strainers, fallen trees.
WW 1/1+ (2).

7.9 Bridge. Average rated discharge 0,9 m³/s. The current strong, small rapids, can be strainers, fallen trees. The river to the mouth flows through small forests, width 4-7 m.
5.1 right Trumpe. right Lapiai. The runoff of the river doubles. Average gradient to mouth 681 cm/km. The river width 7-10 m.
4.7 left the brook. On right bend of the river rapid. The river drops 0.7 m. Downstream the river for a short quiet. Below to the mouth current strong, small rapids, stones, boulders.
0.3 Gargzdai - Kartena road bridge. right Zvelsenai.
0.0 The Zvelsa flows into the river Minija.