Agno River is a river in the Philippine island of Luzon, in the province of Pangasinan. It is the fifth largest river system in the country with drainage area of 5,952 km². It originates in the Cordillera Mountains and empties into the South China Sea via the Cordillera Mountains. The river is 206 km long. Roughly 2 million people live in the Agno River Valley and it comprises one of Philippines’ larger population clusters.
The Agno is the largest Philippine river in terms of water discharge, draining around 6.6 cubic kilometers of fresh water into Lingayen Gulf, or almost 70% of the total fresh water input into the gulf.
The headwaters of Agno River are at the slopes of Mount Data in the Cordillera Mountains at an elevation of 2,090 m, where it drains Cretaceous to Paleocene igneous basement rocks, and marine siliciclastic and carbonate rocks. Of its total length, about 90 kilometers runs through mountainous terrain and canyons.
As the river descends following a southerly course, it exhibits a braided channel pattern. It then transforms into a southwest-directed meandering river as it crosses the Central Luzon Plain. From its confluence with the Tarlac River emanating from the south, the Agno River then veers northward while draining the eastern flanks of the Zambales Mountains.
The Agno’s principal tributaries include the Pila, Camiling, Tarlac and Ambayoan Rivers. The main branch of the Agno River is Tarlac River which originates from Mount Pinatubo (elevation 1,745 m) in Tarlac and joins the Agno River at Poponto Swamp near Bayambang. The swamp has an area of about 25 square kilometers and temporarily retains flood waters from Tarlac River. – wikipedia.org