The general slope of the plateau is toward the N., and the drainage of the state is chiefly through the above-named rivers - the principal tributaries of the Araguaya being the Grande and Vermelho, and of the Upper Tocantins, the Manoel Alves Grande, Somno, Paranan and Maranhao.
Although the northern and southern extremities of Goyaz lie within two great river systems - the Tocantins and Parana - the upper courses of which are navigable, both of them are obstructed by falls.
On the western frontier a northern extension of the great central chain of Goyaz forms the water-parting between the drainage basins of the Sao Francisco and Tocantins, and is known at different points as the Serra do Paranan, Serra de Sao Domingos and Serra das Divisoes.
The Mantiqueira-Espinhago chain shuts out the streams flowing directly east to the Atlantic, and the boundary ranges on the west shut out the streams that flow into the Tocantins, though their sources are on the actual threshold of the state.
The latter rises on the western slopes of the Serra da Matta da Corde, and one of its northern tributaries has its source in a "knot" of the Serra dos Pyreneos, from which streams flow eastward to the Sao Francisco and northward to the Tocantins.
