From its source at Laguna Negra (eastern slopes of the Andes, 3,600 masl), the Upano River flows in a northeast direction towards the Palora River; but suddenly it makes a U-turn and heads toward the south to join the Paute River, and eventually the Santiago River, an affluent of the Amazon. Along its ca. 100-km course, the Upano River has cut a channel 50 to 100 m deep, and 1,000 to 2,400 m wide, flanked by steep walls, known locally as “barrancos.” The strong current characteristic of this river makes the Upano unsuitable for navigation and unpredictable for crossing, as the stream constantly moved across the channel. In the past three decades, however, the river-bed has remained steady, giving room for the formation, on the channel, of a relatively wide flood plain, where a permanent settlement (Playa de San Luis) of daring colonists has been established.
The Upano River cuts across a large plain (located at 1,200-1,500 masl) sloping down towards the south and east until reaching the Cutucu Cordillera. On the right bank, the plain is a sort of a plateau (Eden) with hardly any topographical feature worthy of notice, except for small streams that cut across it to fall into the barranco. Towards the south, this plateau ends at the edge of a 70 m-deep ravine cut by the Domono River flowing eastward to the Upano River. At the base of this ravine the terrain gives way to a lower plain that runs south for several kilometers to the present day towns of General Proano and Macas. On the left bank a similar situation occurs. The Balcones plateau rolls down to Huapula (where the Sangay complex is located), and then drops to the plain extending south to the present day towns of Santa Rosa and Sevilla del Oro (the latter located opposite Macas).
From a geological point of view, the Upano Valley is built on huge deposits of clasts and sand, mostly of volcanic origin. The history of the nearby Sangay volcano (5,230 m high) is not well known, but geological survey carried out by Hall (1977:83) indicates the existence of at least three craters in a position that suggests a migration of vents towards the west. The soils of the upper Upano Valley have been described as “hydrandepts” of rather low fertility and high water content, lying on volcanic ashes, usually weathered.
As a general rule, the soil profiles consist of a black vegetal layer 10-20 cm thick, followed by an intermediate layer lighter in color (usually around 30 cm thick), and a thicker yellow layer (2 m and more) that constitutes the substratum of the profile. Both colonists and indigenous Shuar consider the Upano Valley fertile enough for their agricultural practices. The Upano river valley is heavily deforested due to the intensive colonization from the highlands that has taken place since the 1920s.
World History
