Navarra's principal river, an Ebro tributary flowing south through Pamplona. The Arga rises in the western Pyrenees and joins the Aragón before reaching the Ebro (Mediterranean drainage — no Atlantic salmon access). Limestone and granite headwaters transition to sandstone near the city. Productive brown trout water with pool-and-run structure. Dry fly and nymphing for summer trout in clear upper reaches; water turns brownish during spates.
- Mixed