The river Jiesia flows in Marijampole, Prienai and Kaunas districts, the river Nemunas left tributary. Length of the river 68.5 km, the basin area 499 km ². The source at Pajiesys village, 6 km west from Igliauka willage. Flows to the northeast. Flows into the river Nemunas 214.5 km from its mouth, at Kaunas city. Average gradient 115 cm / km. In lower section banks are steep, in the riverbed is a lot of boulders. The valley width 130 - 150 m, in lower section (from Rokai village) up to 800 m. Valley slopes in middle and lower sections steep, height 30-60 m. Floodplain width 60 - 100 m, during floods flooded. The river is characterized by sudden, brief flood not only in spring but in winter too; they are sometimes higher than in the spring. Average rated discharge at the mouth 2.99 m³/s.

At higher water level. Spring, or after heavy rains.
Rapids, dam, a few strainers.
WW 0/1+ (2).

19.4 left Pajesys. On the banks bushes, trees. The river width approx. 7 m. In the riverbed can be bushes, strainers, beavers dams. Current speed average.
18.4 left Slapaksna. right Kairiuksciai. Average gradient to the brook Kume 118 cm/km. The river width to mouth 10-15 m. Average rated discharge 214 m³/s.
17.0 left the brook J-3. left Ilgakiemis.
14.9 left Rasnava. Current gradually accelerating, in riverbed stones, first small rapids.
13.0 left Kume. Average gradient to the brook Aukstazys 200 cm/km. In the river small rapids to the mouth.
12.1 left Aukstazys. Average gradient to the brook Maisys 100 cm/km.
11.7 right Vycius. The remains of the bridge. In the riverbed concrete ingots. left Garliava.
11.4 1st railway bridge. Under the bridge rapid.
10.8 left Maisys. Average gradient to the brook Sanasa 120 cm/km.
10.4 2nd railway bridge. Under the bridge rapid.
9.1 3rd railway bridge. Under the bridge concrete rapid (height of 3 cascades 2.5 m). Dowstream the banks high. Slopes, outcrops.
7.2 Low dam. Height approx. 1 m. Navigable on left side. left Razickiai.
5.8 4th railway bridge.
5.4 Kaunas - Marijampole road bridge. 40 m downstram bridge. right Rokai.
3.6 left the brook J-1.
1.1 left Sanasa. Average gradient to the mouth 73 cm/km.
1.0 Pedestrian bridge. left Kaunas. Naujoji Freda. Just before the mouth the river calms.
0.1 Bridge.
0.0 The Jiesia flows into the river Nemunas. 300 m downstream right hillfort Pajiesys (Napoleon's cup).