The Neckar is a tributary of the Rhine in Germany with a length of 362 km - with the longer Eschach upper reaches even 380 km - which drains the central part of Baden-Württemberg with a catchment area of almost 14,000 km². At its mouth, an average of 145 m³/s flow off. Hydrologically, the Neckar is the fifth largest tributary of the Rhine after the Aare, Maas, Moselle and Main and the twelfth largest river in Germany in terms of both length and flow.
Source: Wikipedia