A Peruvian court has ruled that plans to dredge parts of the Amazon and its major tributaries must be suspended until indigenous communities along the rivers are consulted.

The ruling by the Superior Court of Loreto, in northeastern Peru, could set a precedent in the country, according to Juan Carlos Ruiz, a lawyer at the non-profit Legal Defense Institute (Instituto de Defensa Legal, IDL).

“This is the first case involving an (infrastructure) megaproject that has been won by an indigenous organization,” said Ruiz, who filed the case on behalf of Acodecospat, an association of Kukama communities in the lower Marañón River valley.

For the Kukama Kukamiria in the lower Marañón River valley, the river is the home of the boa that gave birth to the first of their people. It is also the source of water for cooking, washing, drinking and bathing, as well as the main transit route through a region with almost no roads.

And spirits—including family members who drowned and whose bodies were never recovered—live in its depths.

The proposed waterway or “hydrovia” is part of a South American plan to improve infrastructure connecting the region’s countries. It would involve dredging what officials call “bad spots”—shallow places and snags of submerged tree trunks—along the Amazon River and three Peruvian tributaries, the Marañón, Huallaga and Ucayali River.

But local fishermen say those are “good spots”—places where fish gather and river spirits rest.

The $64 million project also calls for signals marking the channel a system to transmit information about water levels. The goal is to make the rivers navigable year-round to the port cities of Yurimaguas and Pucallpa, where freight from Brazil can connect with highways to the coast.

The Peruvian government had called for bids on the project, but suspended the process in February, when only one of the eight companies that had expressed interest actually presented a bid.

Some observers said the reluctance may have been due to a lower court ruling in Acodecospat’s favor and the appeal that was pending at the time before the higher court.

At a public hearing in February in Nauta, a port town on the Marañón River, officials from the Ministry of Transportation and Communications told community leaders that the government would not go ahead with the project until a consultation was held.

A law requiring prior consultation of indigenous communities when a development project or government plan would affect their communal rights took effect in 2011.

In arguing the case, Ruiz said indigenous organizations should be consulted on both the terms of reference for the project and on the environmental impact study.

The superior court ruling, however, leaves some unanswered questions about the consultation process. In its decision, the court said it lacked the authority to dictate when the consultation should occur.

While the appeal was under way, officials from the Ministry of Transportation and Communications and ProInversion, the government’s investment promotion agency, met with leaders of indigenous organizations from the four affected watersheds to discuss the consultation process.

The consultation plan will be announced formally on May 19, according to the government news agency, and the consultation is to be completed by August.

At the public hearing in February, Kukama leaders told government officials that they were worried about the impact of dredging on fish and riverside fields where they grow corn, rice and bananas.

They also expressed concern about the safety of river travel, as the canoes generally used by local families can be swamped by the wake of large vessels.

Several speakers mentioned the impact on the spirits that live in the river, a topic that has generally gone unnoticed in discussions of the waterway.

One potential problem with the planned dredging is that little is known about sediment flows in the targeted rivers, according to Jorge Abad, a Peruvian civil engineer at the University of Pittsburgh’s Center for Research and Education of the Amazonian Rainforest.

Abad is leading the first effort to map the sediment flows in the four rivers that would be affected by the dredging. Without basic data, he said, it is impossible to predict potential environmental impacts of the project.

“First you have to understand the river,” he said, “and I don’t think we’re at the point of understanding our rivers yet.”