The Rio Pacaás Novos is a river in the western state of Rondônia, Brazil, and is a significant tributary of the Mamoré River. It flows through a region of notable ecological importance, as its tributaries are encompassed by the Resex Estadual Rio Pacaás Novos, a state-level extractive reserve. This designation indicates a protected area focused on sustainable use and conservation, which may influence regulations for visitors. Paddlers should be aware of and respect any local rules established for this reserve. The river's character is defined by its role within the larger Amazonian watershed system. Its waters support a specific aquatic biotope, suggesting a distinct ecological community. The water parameters from this habitat include a temperature of approximately 26.5°C (about 80°F), a pH of 6.5, and very soft, acidic water with a general hardness near 0. These conditions are consistent year-round in this tropical region, indicating stable, warm water temperatures suitable for paddling across seasons. The river's aesthetic is one of a typical Amazonian tributary, with its associated fish and plant life contributing to the environment. Direct information on specific access points, recommended routes, hazards, or facilities for paddlers is not detailed. The presence of the extractive reserve suggests that while the river is used, activities are likely managed to protect both the environment and the livelihoods of traditional communities, so prior inquiry into access permissions is advisable for trip planning.