The Olona is a 131 km long Italian river, which runs through the provinces of Varese, Milan and Pavia.

The Olona river in Nerviano

The Olona river passes through the deep Olona Valley, cut in the poruous soils of the upper Po Valley, eventually flowing in the plain after Legnano. It is in the Olona valley part that the river gets much of the industrial pollution which has made it a byname for venomous waters for decades. Only in recent years attempts to restore the river's ecology have proven at least partially successful. After Legnano, the Olona river flows in the plain until Milan, usually contained in narrow artificial banks. New expansion basins are being constructed to prevent floodings, which are rare but can be devastating under conditions of sudden intense rain in the upper river flow.

The river passes through Milan mostly under road level. In Milan the Olona cedes part of its water to the Lambro meridionale, to later continue southward in the Bassa (lower Lombard Po Valley). The Olona flows into the Po near San Zenone al Po.

The Olona river counts 39 tributaries. The principal tributaries are the torrents Vellone, Bevera Varesino, Lanza (or Gaggiolo), Bozzente, Lura, Merlata and Mussa.

References

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