The Paranaiba flows north out of the Mata da Corda serra at an average elevation of 760 meters. For its first 370 kilometers, it crosses an underpopulated stretch of Minas Gerais, passing through the town of Patos de Minas at 770 meters. The slope is gentle, about 25 centimeters per kilometer. Small tributaries enter from the flanks of the Magalhaes peak and the Serra of Barbaca. At kilometer 729, the river meets the Verde River near the town of Contendas in Goias and bends sharply, taking up the border between Minas Gerais and Goias. That border-making continues for hundreds of kilometers. The middle Paranaiba cuts through diamond-bearing rock in what's called the triangle zones of Minas Gerais and Goias. Tributaries here have fed diamond prospectors for centuries. Valleys are narrow, banks rise steeply to 25 or 60 meters, and the river's slope steepens to 1.2 meters per kilometer.

The lower Paranaiba is a chain of reservoirs. Three major dams punctuate its course, all generating electricity for the southeast's industrial heart. The Itumbiara Dam, in operation since 1981 at Aporao, generates 2,082 megawatts and ranks as the most powerful in the Furnas hydroelectric complex. Downstream, the São Simão Dam adds another 2,680 megawatts. The Cachoeira Dourada station near Itumbiara, now operated by Endesa, feeds Goiania and Brasilia. But the dams cost Brazil a natural wonder. The São Simão Channel, also called the Canal de São Simão, was a narrow gorge carved into basalt, 23 kilometers long and 35 meters deep, on the Minas-Goias border. Its waters split into two parallel arms before merging again in a corridor of waterfalls. The São Simão Dam flooded it. The channel no longer exists. It was one of the greatest ecological losses in modern Brazilian history, and like the Guaira Falls downstream, it was traded for megawatts.

The Paranaiba gathers water from a dense network of tributaries. The São Marcos enters at kilometer 661 from the right bank. The Perdizes comes in at kilometer 633 from the left. The Bagagem enters at 596. Below that stretch, the Verissimo, the Corumba, the Santa Maria, the Jordao, the Araguari, and the Piedade all feed the middle Paranaiba. Together they drain a vast area of western Minas Gerais, southern Goias, and northern Mato Grosso do Sul. Agriculture occupies 20 to 50 percent of the river corridor, with the rest divided among pasture, cerrado, and protected areas. At kilometer 400, the river begins running on the famous basalt plate that underlies much of the Paraná basin. This geological signature will follow the water all the way to the sea.

The Paranaiba is navigable only for 180 kilometers, in the artificial lake of Ilha Solteira, as far as the São Simão Dam. Beyond those limits, the dams block passage and the natural rapids defeat shipping. There have been proposals to extend navigability deeper into central Brazil, potentially reaching Brasilia, but they remain proposals. Meanwhile the river carries pressures its planners did not anticipate. Bank erosion from sand extraction is severe. Original forest cover has largely been cleared. Practically 100 percent of the towns in the basin dump untreated sewage directly into its waters. Goiania, the state capital, sends 95 percent of its sewage untreated into the Meia Ponte, a Paranaiba tributary. The diamonds that once fueled prospector dreams are mostly gone. The hydroelectric potential has been substantially tapped. The pollution remains a public-health problem that outruns both the economic development and the ecological losses.