Arari River

The Arari River (Portuguese: Rio Arari) is a river of Marajó, which itself is an island in the mouth of the Amazon. It is located in the state Pará in northern Brazil.

The river originates in the south of Lake Arari. Here it flows through swamp areas called mondongos that are normally flooded during the wet season. The beginning of its course is rather winded, becoming more straight after passing Cachoeira do Arari. Here the river is covered with aninga plants, giving it a dark and muddy aspect. Close to its mouth in Marajó Bay the river widens and its banks are more rocky. Numerous lakes line the banks of the river, particularly in the middle and downstream sections, the largest being around 10 km (6.2 mi) long and 0.6 km (0.37 mi) wide.

Depending on seasonal changes of the water level in Marajó Bay, the river sometimes flows in the opposite direction for part of its course. This introduces a seasonality in all its physical and chemical characteristics, like oxygen and nitrogen levels, temperature, acidity, turbidity, water quality and Trophic State Index. The land upstream is used for large water buffalo farms, which saturate the river with nutrients. Smallholder farmers use the river water for domestic use, agriculture and fishing. Tamoatá fish from the basin of the Arari represents 6% of sales in Ver-o-Peso market in Belém.