The Trebbia river spring is located on the oriental side of an important orographic and hydrographic knot , the Antola Mountain massif and its ramifications.
The river, whose name comes from Latin "Trebia", is being born along the Prelà Mountain slopes at 800m above sea-level, flowing for 118 Km maintaining a SW-NE direction.
The meandering watercourse, after a tortous run, little ponds and bends, flows into the Po river, near Piacenza, even if its spring is quite close to the Ligurian sea.
The regular shaped basin of the valley almost maintains a constant wideness.
The torrential regimes of the tributeries are quite changeable during the year.
An important tributary is the Brugneto stream that flows into the Trebbia river before Montebruno town, after having filled up the homonym artificial lake.
Afterwards there is the Cassingheno stream near Due Ponti town, and the Terenzone stream to the south of Gorreto that flows down the slopes of the Carmo Mountain.
In the upper part of the valley on the right slope the limited impluvium wideness  prevents the formation of big basins, even if there are numerous and steeply  (Giassina stream, Bocco stream, Cavagnaro stream...).
Streams of bigger length are formed only along the slopes of Montarlone mountain because of the valley getting wider. Some of  these are the Sermigliasca stream, the Pescia stream flowing between the  Fontanigorda town and Casanova town, and the Gramizzola stream, flowing down into the Trebbia river close to Rocca dei Corvi and on the border between Liguria and Emilia.