The Coaque's headwaters lie inside the Mache-Chindul Ecological Reserve, in the Bilsa Biological Station - a pocket of coastal wet forest that catches moisture off the Pacific and holds it against the first ridges of the Andean foothills. Water collects there, drops through ferns and bromeliads, and works its way down through a landscape that looks nothing like the open beaches it will eventually reach. By the time the river reaches the coastal plain, it has become a working river: irrigating small farms, carrying sediment, and carving a shallow channel across soft sedimentary rock on its way to the sea.

In early 1531, Francisco Pizarro's third expedition - the one that would end at Cajamarca with the capture of Atahualpa - landed on this coast and spent months at a Native settlement called Coaque, near the river mouth. His men were sick, tired, and suspicious of the inland journey ahead. They looted the Indigenous village of gold and emeralds, sent some of the treasure back to Panama to entice reinforcements, and waited. A historical marker and the surviving place name still tie this quiet river to that moment, when the direction of a continent's history hinged partly on whether Pizarro's depleted force could regroup here long enough to march south.

The modern Coaque is less famous but more demanding. In March 2012, landslides in Piedra Maluca upstream dumped so much mud into the channel that the river dammed itself, flooding homes in the communities of Coaque, Quiauque, Colisa, and La Playa. Police and military shut the roads, and the contractor Equitesa - which was building the Pedernales-to-San Vicente highway - was given the unglamorous job of getting the river moving again. By 2013, crews had excavated more than 254,000 cubic meters of earth and cut a new channel 420 meters long and 26 meters deep, with tens of thousands more cubic meters of widening still to come.

The same river that nearly drowned a string of villages is also supposed to save them. In 2013, Ecuador's National Water Secretariat commissioned a Spanish engineering firm to study a multi-purpose scheme that would link the Coaque and Tachina basins with a diversion dam and a seven-kilometer canal. The plan, if built out, would irrigate 2,100 hectares of farmland and pipe drinking water to about sixty thousand residents of the Pedernales canton. For a rural coast where tropical downpours alternate with long dry months, the project asks a simple question that Coaque has posed since Pizarro's day: how do you share a river that is never quite the same year to year?

From the air, the Coaque looks almost incidental - a pale line winding through green fields and patchy forest, reaching the sea south of Pedernales. On the ground it is the spine of a way of life. Small fishing settlements dot the mouth. Inland, farms depend on its flow. The ecological reserve at its headwaters is a last refuge for coastal wet forest in a province that has lost most of its original tree cover. The Coaque does not make the tourist brochures, and it probably never will. But trace it from Bilsa to the Pacific and you pass through most of what Manabí Province is about: mountains, mud, memory, and the patient work of keeping a river in its channel.