Community-based monitoring reveals the impacts of the permanent river drought imposed by the Belo Monte Hydroelectric Power Plant at Volta Grande do Xingu, Amazonia

Hydroelectric dams, once seen as clean and renewable energy sources, have been the subject of extensive research, particularly concerning their socio-environmental impacts. The Belo Monte Hydroelectric Power Plant (HPP) relies on the operation of two dams, diverting water from a 130 km stretch of the Xingu River to generate energy, disrupting the natural flooding cycle along the Volta Grande do Xingu (VGX) and creating a riverine hydrological condition equivalent to a prolonged extreme dry season in the watershed. Before the Belo Monte HPP, local communities relied on the predictability of the seasonally flooded forest and the synchrony of the reproductive cycle of a highly diverse fish assemblage. VGX residents observed the transformation firsthand, noting the water discharge shortage that critically undermined the river's capacity to sustain vital ecosystem processes that support local people's lives. The Belo Monte HPP environmental licensing process ignored the vital link between the river's flood pulse, the aquatic and seasonally flooded ecosystems, and the traditional lifestyles of VGX residents. The local communities reacted and sought partnerships, establishing the Independent Territorial Environmental Monitoring Program (MATI-VGX). Data acquired by the MATI-VGX evidenced the drastic transformations of traditional lifestyles, shifts in fishing practices, and a significant decline in fishing yield, jeopardizing food sovereignty and security. Here we present evidence of hydrological-induced disruptions in ecological cycles along the VGX, which are intrinsically connected to the modes of life of local populations. To ensure the ecological sustainability of the VGX, the Belo Monte HPP operation must change to support key spawning areas, maintain water quality, avoid short-term water discharge fluctuations, and emulate natural interannual discharge variability, mitigating the flood pulse disruption. Local ecological knowledge should never be ignored in projects where local communities are the most affected. These communities should be central in decision-making regarding socio-environmental impact assessment, mitigation, and monitoring.