What is the importance of the Orinoco River in the novel, Dinosaur Summer?

The Orinoco River introduces additional elements of danger beyond the risks arising from the wild and inhospitable river itself; the greed and ambition of men now threaten the expedition. Venezuela's politics are in turmoil, with the army near El Grande ignoring orders from its government and basically operating as a law unto itself. Military leaders fear the possible reopening of El Grande because an Indian who braves the plateau and returns alive could become a unifying leader for local Indian tribes that resent the control asserted by the army.