The reserve is triangular shaped by the Marañón River in the north and Ucayali River in the south, just before their junction which is the origin of the Amazon River. Its main purpose is to preserve the ecosystems of the Omagua Natural Region, and also to promote the sustainable development of the local towns.
The shortest route is Iquitos – Nauta by highway and then a trip on the river from Nauta to the village, Community of 20 de Enero, about three to four hours by boat. To be able to enter, you must request permission from INRENA and pay the corresponding fees.
Inside the reserve, there are three river basins: the Pacaya River basin, the Samiria River basin, and the Yanayacu-Pucate River basin. There are also numerous lakes, gorges, canals, and oxbows. It has an annual monthly temperature between 20°C (68°F) and 33°C (91°F) and an annual rain fall of 2000 to 3000 millimeters, which allows for its huge biodiversity: 527 bird species, 102 mammal species (among them the pink dolphin), 69 species of reptiles, 58 species of amphibians, 269 fish species, and 1024 species of wild and cultivated plants. The reserve is a refuge for different endangered species like the Arrau turtle (Podocnemis expansa), the spider monkey (Ateles sp.), the giant river otter (Pteronura brasiliensis), the scarlet macaw (Ara macao), Cedrela odorata trees, and others. It is also contains the most extensive area of protected floodable forest (várzea) in the Amazon rainforest.
There are diverse protection and natural resource management projects like the one aimed at repopulating the Taricaya and the Charapa river with turtles in the artificial beaches of the reserve. The local population is involved in the projects. On the edges of Pacaya-Samiria on the banks of the Marañon and Ucayali Rivers, more than 42.000 people live grouped in ninety-four communities and another 50.000 inhabit the 109 villages in the buffer zone. Almost all of them make a living from fishing, farming, or hunting and wild fruit and greens picking.