The Iecava is the largest tributary on the right side of the Lielupe river, which originates in the Ellītes bog in Daudzese parish. Opinions differ on the length of the Iecava, as its middle reaches are so winding that measuring instruments are confused.

In its course, the Iecava is a very unpredictable and tricky lady, with deep and easily navigable places suddenly alternating with substantial shallows. Today, however, much of the Iecava’s course has been regulated, straightened and many tributaries remain. The river’s natural outlet into the Lielupe is 4 km downstream of Jelgava, but much of the water drains through the 19th-century Devil’s Ditch and the Garoze to the Lielupe upstream of Jelgava.

The river is navigable all year round, some sections are not navigable in summer, the section from Lambārte has many fallen trees.

The total length of the river is ~155 km.