The Pastaza (the ancient river Sumatara) is a large tributary to the Amazon River.
It has its headwaters in the province of Tungurahua, where the Tambo River joins the Latacunga River, near the foot of the Volcano Tungurahua, flowing south-east towards the Amazon Basin. It is very shortly thereafter dammed by the Agoyan hydroelectic project, which has made a large, silty lagoon just below the town of Banos. The Agoyan dam was placed in that location specifically to leave the famous Falls of Agoyan, about 5 km further downstream, intact. In Tungurahua, the Pastaza is a very fast whitewater river with class-4 rapids; it is often used for whitewater rafting although it is not considered to be of the same quality as the Tena River and is therefore less popular for the sport. The Troncal Amazonas highway parallels the river from Banos to Puyo, passing through seven tunnels, and four major waterfalls that are touristic destinations for many Ecuadorians (Agoyan and Pailon del Diablo being the most popular.) Just past the town of Santa Inez, the Pastaza River crosses into the province of Pastaza, where it forms the boundary between that province and Morona-Santiago. There are no major fisheries on the Pastaza River - it is primarily used as a means of transport by canoe. Its rise and fall are rapid and uncertain, and it is shallow and full of sandbanks and snags. Flooding occurs seasonally. After cutting through Ecuador, the Pastaza passes into Peru at a point about 60 miles west of the mouth of the Huallaga.
The Pastaza has numerous tributaries, both above and below the hydroelectric dam. These contribute to its rapid flow and to its tendency to flood. On the highway side of the Pastaza, a tributary river occurs about every 3-4 km for a stretch of about 50 km; on the opposite bank, the number of tributaries is slightly lower. Major rivers, including the Pindo, the Puyo, and the Bobonaza, also feed the Pastaza.
In Ecuador, there are very few bridges across the Pastaza. The most significant ones are in Tungurahua province - namely a large span over the exact point of headwaters, just north of Banos, and the secondary span created by the Agoyan dam. After this, bridges tend to be of the suspension type, suitable for foot or small vehicle passage only. However, it is notable that the Pastaza can be forded during the dry season in a 4x4 truck, going across the floodplains below Mera.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Pastaza River