The Unini River is a river located in the Amazonas state in north-western Brazil. It serves as a right tributary of the Rio Negro.

Course

The Unini River originates from the confluence of the Água Preta stream and the Preto River. From there, it flows eastward towards the Rio Negro, serving as the border between the Rio Unini Extractive Reserve Extractive Reserve to the north and the Jaú National Park to the south. The river basin has about 1,500 streams and over 1,000 lakes, with an estimated length of 400 km from its mouth to the headwaters. The basin covers approximately 2689644 ha. The largest tributaries are the Papagaio, Paunini and Solimõezinho streams. The Unini River is characterized by its generally acidic water with minimal suspended material. Its meandering course, along with its tributaries, gives rise to a diverse array of aquatic environments, including lakes, rivers, creeks, and flooded forests. Water levels in the river exhibit seasonal fluctuations, with the lowest levels typically occurring between October and November, and the highest levels between June and July. The range of water levels vary from minimum to maximum between 11.26 and 15.75 m.

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