The Trombetas is long, and is navigable by 500 ton vessels for a stretch of . The Trombetas river gives birth to very many rivers, including the Anamu river. It is formed by the junction of the
Poana and Anuma rivers on the border between Brazil and
Guyana. Where it meets the Paraná de Sapucuá it takes the name of lower Trombetas, and reaches up to in width, with the stream divided by several long and narrow islands. It runs through the municipalities of
Oriximiná,
Terra Santa,
Óbidos and
Faro. The river basin has an area of about , with an intricate pattern of tributaries including the Poana, Anamu, Turuna, Inhabu, Mapuera and
Paru de Oeste. In the
Saracá-Taquera National Forest the main streams in the Trombetas basin are the Papagaio, Água Fria, Moura, Jamari, Ajará, Terra Preta and Saracá. Its
confluence with the Amazon is just west of the town of
Óbidos, Pará in
Brazil. Its sources is in the
Guiana highlands, but its long course is frequently interrupted by violent currents, rocky barriers, and rapids. The inferior zone of the river, as far up as the first fall, the
Porteira, has but little broken water and is low and swampy; but above the long series of cataracts and rapids the character and aspect of the valley completely change, and the climate is much better. The river is
navigable for above its mouth. The river reaches its highest levels in April and May, since the rainy season usually peaks in April. ==Region==